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29* 



ELEMENTS 



OF 



CHEMISTRY, 



INCLUDING THE APPLICATIONS OF THE SCIENCE IN THE ARTS. 



WITH NUMEROUS ILLUSTRATIONS. 



BY 

THOMAS GRAHAM, F.R.S. L. & ED. 

PROFESSOR OF CHEMISTRY IN UNIVERSITY COLLEGE, LONDON; PRESIDENT OF THE CHEMICAL 

SOCIETY; CORRESPONDING MEMBER OF THE ROYAL ACADEMIES OF 

SCIENCES OF BERLIN AND MUNICH, &.C. 



WITH NOTES AND ADDITIONS 



BY 



ROBERT BRIDGES, M.D. 



PROFESSOR OF GENERAL AND PHARMACEUTIC CHEMISTRY, IN THE PHILADELPHIA COLLEGE OF 
PHARMACY, AND ONE OF THE EDITORS OF THE AMERICAN JOURNAL OF PHARMACY. 



# 

PHILADELPHIA: 

LEA & BLAN CHARD. 
1843 



3£VtUVt% according to Act of Congress, in the year 1843, by LEA & BLANCHARD 

in the Clerk's Office of the District Court of the Eastern District of Pennsylvania. 






GRIGGS & CO., PRINTERS. 



PREFACE. 



The important bearings of the laws of heat, particularly in reference to the 
physical condition of matter, have led to their consideration before the chemical 
properties of substances, in this as in most other elementary treatises on che- 
mistry. Light is then shortly considered, chiefly in reference to its chemical 
relations. The principles of its Nomenclature, in which, compared with many 
sciences, chemistry has been highly fortunate, are then explained, together with 
the Symbolical Notation in use, by means of which the composition of highly 
compound bodies is expressed with the same palpable distinctness, which in 
arithmetic attends the use of figures, in place of words, for the expression of 
numerical sums. 

A considerable section of the work is then devoted to the consideration of the 
fundamental doctrines of chemistry, under the heads of Combining Proportions, 
Atomic Theory, Doctrine of Volumes, Isomorphism, Isomerism, Constitution of 
Salts, and Chemical Affinity, including the propagation of this action through 
metallic and saline media, in the voltaic circle. 

The materials of the Inorganic world are then described, under the two di- 
visions of non-metallic elements and their compounds, and metallic elements and 
their compounds. 

Lastly, the numerous compounds of the Organic world are discussed. In 
this department, a most extraordinary progress has been made within a very 
short period. The study of organic chemistry has also been much facilitated by 
classification, and the arrangement under compound Radicals, introduced by M. 
Liebig. 

It was now obvious that the science was sufficiently advanced to be applied 

1* 



VI PREFACE. 

to the elucidation of the great questions of vegetable and animal physiology. 
A condensed view is given of the new discoveries in the former department, 
and also of the important conclusions respecting the animal functions of respi- 
ration and digestion, results which are entirely new, and now enter for the first 
time into a systematic work on Chemistry. 

University College. London. 



PREFACE 



TO THE 



AMERICAN EDITION. 



The Elements of Chemistry, an American edition of which is now offered to 
the Professors and Students of chemical science, is deservedly held in high 
estimation, not only from the acknowledged talents of the author, but also from 
the abundance of facts drawn from every available source, and the clear and 
comprehensive style and the judicious arrangement in which they are laid 
before the reader. 

This work fully represents the progress of the science up to the date of its 
publication. Sufficient detail has been observed, to adapt the treatise to the 
wants of the student, as an elementary text book, and also render it available 
as a work of reference. At the same time the labour of research is much 
lightened for those who are desirous of pursuing any subject into minute detail 
by copious references to the sources and the original papers from which informa- 
tion has been derived. 

The task of the American editor has been to correct any inaccuracies or 
misprints, and to add any important observations which may have appeared 
subsequently to the publication of the original work. The additional matter is 
principally in the form of notes, to which the initials of the editor are appended, 
and in the few instances in which it was considered that the text was the more 
appropriate position, the observations are included in brackets accompanied in 
like manner by the editor's initials. 



Vlll PREFACE. 

To render any book useful to students and fully available as a work of 
reference, a copious and judiciously selected index is absolutely necessary. 
This will be found in the present work, and especial care has been taken to 
preserve this feature unaltered and rather to increase than diminish the facilities 
in this important point. 

Philadelphia, August, 1843. 



CONTENTS. 



PART I. 
CHAPTER I. 

Page 

Heat ------ 25 

Expansion and the Thermometer - - - 25 

Specific heat - - - - - 39 

Communication of heat, conduction 41 

Radiation - 43 
Transmission of heat through media, and effect of 

screens ----- 45 

Equilibrium of temperature 48 

Fluidity as an effect of heat ... 50 

Vaporization ----- 54 

Distillation ----- 63 

Evaporation in vacuo - 64 

Gases ------ 68 

Diffusion of gases ----- 70 

Spontaneous evaporation in air - - 75 

Hygrometers - 76 

Drying ------ 78 

Nature of heat ----- 80 



CHAPTER II. 

Light - - - - - - .81 

CHAPTER III. 

Chemical nomenclature and notation - - 85 

Combining proportions - 95 

Atomic theory - - - - - 103 

Specific heat of atoms - - - - 105 

Volumes of atoms in the gaseous state * - 107 



CONTENTS. 

Page 
Isomorphism - - - - - 115 
Classification of elements - - - - 119 
Dimorphism - - - * - 124 
Isomerism - 127 
Arrangement of the elements in compounds, consti- 
tution of salts - - - - 129 
Sect. II. Chemical affinity - - - - 145 
Solution ----- 146 
Order of affinity - - - - - 149 
Influence of insolubility - - - - 151 
Catalysis, or decomposition by contact - - 155 
Inductive affinity - - - - - 156 
Magnetical polarity - - - - 159 
Magnetical induction - - - - 160 
Chemical polarity and induction - - - 161 
Simple voltaic circle - - - - 162 
Compound voltaic circle - - - - 166 
Solid elements of the voltaic circle - - 169 
Liquid elements of the voltaic circle - - 171 
General summary - 176 
Voltaic instruments - - - - 180 



PART II. 

CHAPTER I. 

Non-metallic Elements. 

Sect. I. Oxygen ------ 185 

Combustion in air - - - - 192 

Sect. II. Hydrogen - - - - - 193 

Water - - - - - - 197 

Peroxide of hydrogen - - - - 201 

Sect. III. Nitrogen ------ 203 

The atmosphere - - - - • - 204 

Analysis of air - - - - 208 

Nitrous oxide, or protoxide of azote - - 211 

Nitric oxide - - - - - 213 

Nitrous acid - - - - - 215 

Peroxide of nitrogen - - - - 216 

Nitric acid - 217 

Sect. IV. Carbon 221 

Diamond ------ ib. 

Graphite - - - - ib. 

Varieties of Charcoal - 222 

Carbonic acid - 224 

Carbonic oxide ----- 227 

Sect. V. Boron ------ 228 



CONTENTS. Xi 

Page 

Boracic acid - - - - . - 229 

Sect. VI. Silicon - - - - 2 30 

Silica or silicic acid - - - - 231 

Silicates 232 

Sect. VII. Sulphur - - - - - ' lb - 

Sulphurous acid ----- 234 

Sulphuric acid ----- 236 

Sulphates ----- 239 

Hyposulphurous acid - - - - "'" 241 

Chlorosulphuric acid - 242 

Nitrosulphuric acid - 243 

Hyposulphuric acid - 244 

Sect. VIII. Selenium 245 

Oxide of selenium - - - - ib. 

Selenious acid ----- ib. 

Selenic acid ----- 246 

Sect. IX. Phosphorus ----- ib. 

Oxide of phosphorus - 248 

Hypophosphorous acid ... - 249 

Phosphorous acid ... - 250 

Phosphoric acid ----- 251 

Phosphates ----- 253 

Sect. X. Chlorine 256 

Chlorides 261 

Hydrochloric acid - 262 

Compounds of chlorine and oxygen - - 264 

Hyperchlorous acid - 265 

Hypochlorites ----- 266 

Chloric acid - - - - - ib. 

Hyperchloric acid - 267 

Chlorous acid or peroxide of chlorine - - 269 

Chloride of nitrogen ib. 

Chlorides of carbon - 270 

Chlorocarbonic acid gas, chloride of boron, of silicon, 

of sulphur - - - - - 272 

Chlorides of phosphorus - 273 

Sect. XI. Bromine ------ ib. 

Hydrobromic acid and bromic acid - - 274 
Chloride of bromine, bromide of sulphur, of phos- 
phorus and silicon - - - - 275 

Sect. XII. Iodine ------ ib. 

Iodides 278 

Hydriodic acid ----- 279 

Iodic acid ----- ib. 

Iodates - - - - - -280 

Hyperiodic or periodic acid - - - 281 

Iodide of nitrogen, &c. ib. 

Sect. XIII. Fluorine ------ 282 

Hydrofluoric acid - 283 

Fluoride of boron or fluoboric acid - - 285 

Fluoride of silicon or flosilicic acid - - ib. 



XU CONTENTS. 

CHAPTER II, 

Compounds of hydrogen. 

Page 

Sect. I. Sulphuretted hydrogen - 287 

Persulphuret of hydrogen - 288 

Sect. II. Selenietted hydrogen - 289 

Sect. III. Hydrogen and nitrogen; amidogen, oxamide, sulpha- 

mide, carbamide - - * - - 290 

Ammonia - - - - - 291 

Ammonia and anhydrous oxygen acids - - 293 

Ammonia with anhydrous salts - 294 

Ammonium ----- ib. 

Chloride of ammonium - - - - ib. 

Sulphurets of ammonium - 295 

Nitrate of oxide of ammonium - - - ib. 

Carbonates of oxide of ammonium ib. 

Sulphate of oxide of ammonium ... 296 

Compounds of ammonia and metallic salts - - ib. 

Sect. IV. Hydrogen and phosphorus - 297 

Phosphuretted hydrogen ib. 

CHAPTER III. 

Compounds of carbon. 

Sect. I. Carbon and hydrogen, light carburetted hydrogen, 

safety lamp - - - - - 299 

Coal gas 301 

Structure of flame ----- 302 

defiant gas ----- 303 

Sect. II. Carbon and sulphur, bisulphuret of carbon - - ib. 

Sect. III. Carbon and nitrogen, cyanogen, mellon - - 304 

CHAPTER IV. 

Compounds of phosphorus; sulphuret, azoturet - 305 

CHAPTER V. 

Metallic elements, general observations - - 306 

Arrangement of metallic elements - - - 311 



CONTENTS. Xlll 

ORDER I. 

Metallic bases of the alkalies. 

Page 

Sect. I. Potassium - - - - - - 312 

Potash or potassa - - - - - 315 

Peroxide of potassium - - - - 317 

Sulphurets of potassium ib. 

Chloride, iodide, ferrocyanide - - - 318 

Ferricyanide, cyanide - - - - 319 

Sulphocyanide ----- 320 

Salts of potash : carbonate, bicarbonate, sulphates, ni- 
trate, (gunpowder.) chlorate, hyperchlorate, iodate 321 
Sect. II. Sodium - - - - - - 326 

Compounds of sodium : soda, sulphurets, chloride or 

common salt ----- 327 

Salts of soda : carbonate, (alkalimetry,) bicarbonate, 
sesquicarbonate, sulphate, (preparation of carbonate 
from sulphate,) bisulphate, nitrate, chlorate, phos- 
phates, borax, silicates - 329 

Glass - 328 

Sect. III. Lithium, lithia - - - - ■- 341 

ORDER II. 



Metallic bases of the alkaline earths. 

Sect. IV. Barium ------ 342 

Barytes ------ ib. 

Peroxide of barium, chloride of barium, carbonate of 

barytes, sulphate, nitrate - - - - 343 

Sect. V. Strontium - • - - - - - 344 

Strontia, peroxide of strontium, chloride, carbonate of 

strontia, sulphate, hyposulphite, nitrate - - 345 

Sect. VI. Calcium ------ 346 

Lime, peroxide of calcium, sulphurets, phosphuret, 

chloride of calcium, fluoride - - - ib. 
Salts of lime : carbonate, sulphate or gypsum, hypo- 
sulphite, nitrate, phosphates - 349 
Chloride of lime, or bleaching powder - - 350 
Chlorimetry ----- 352 

Sect. VII. Magnesium ------ 354 

Magnesia, chloride of magnesium, carbonate of mag- 
nesia, sulphate, hyposulphate, nitrate, phosphates, 

borate, silicates ----- ib. 



XIV CONTENTS. 

ORDER III. 

Metallic bases of the earths. 



Sect. VIIL Aluminum - 

Alumina, sulphuret of aluminum, chloride, fluoride 

sulphocyanide - 
Salts of alumina : sulphate, alums, nitrate, phosphate 

silicates - 
Earthenware and porcelain - 
Sect. IX. Glucinum, yttrium, thorium, zirconium 



Page 

358 

ib. 

361 
365 
367 



ORDER IV. 



Metals proper having isomorphous relations with magnesium^ with bismuth. 

Sect. I. Manganese ------ 370 

Protoxide, protosulphuret, protochloride, fluoride, car- 
bonate, sulphate, hyposulphate - - - 371 
Deutoxide of manganese, sesquichloride, sesquicyan- 

ide, red oxide - - - - - 373 

Peroxide of manganese - 374 

Valuation of peroxide of manganese - - 375 

Manganic acid ----- ib. 

Hypermanganic acid, hyperchloride - 376 

Isomorphous relations of manganese - - 377 

Sect. H. Iron _.---* 379 

Smelting clay iron-stone, cast-iron, malleable iron, 

steel ------ 382 

Passive condition of iron - - - - 385 

Protocompounds of iron: protoxide, protosulphuret, 
protochloride, protiodide,protocyanide, ferrocyanide 
of potassium and iron, ferricyanide, carbonate, sul- 
phate, nitrate, acetate, tartrate, titanate - - 387 
Percom pounds of iron : peroxide, black oxide, sesqui- 
sulphuret, perchloride, periodide, percyanide, sesqui- 
ferrocyanide or Prussian blue, persulphates, perni- 
trate, peroxalate, benzoate and succinate - - 390 
Sect. III. Cobalt - - - - - 395 

Protoxide, chloride, carbonate, phosphate, peroxide, 
percyanide ----- ib. 

Sect. IV. Nickel ------ 397 

Protoxide, peroxide, sulphuret, chloride, sulphate, 

nickel silver ----- 398 

Sect. V. Zinc ------ 399 

Protoxide, sulphuret, chloride, iodide, sulphuret * ni- 
trate, phosphate, silicate ib. 
Sect. VL Cadmium - ■ ■* • - * 401 



CONTENTS. XV 

Page 

Oxide, sulphuret, sulphate, alloys - - - 401 

Sect. VII. Copper ------ 402 

Suboxide, subsulphuret, subchloride, subiodide - 403 
Protoxide, chloride, carbonates, sulphates, nitrates, 

oxalates, acetates, alloys ib. 

Sect. VIII. Lead ------ 407 

Suboxide, protoxide, peroxide, minium, or red lead, 
sulphuret, chloride, iodide, cyanide, carbonate or 

ceruse, sulphate, nitrate, nitrites, acetates, alloys ib. 

Sect. IX. Bismuth - - - - - - 413 

Oxide, sulphuret, chloride, nitrates, peroxide, alloys 414 



ORDER V. 

Other metals proper having isomorphous relations ivith the magnesian 

family. 

Sect. I. Tin ----- - 415 

Protoxide, protochloride or salt of tin, protosalts, 
deutoxide, peroxide, bisulphuret or mosaic gold, 
bichloride, or permuriate of tin, alloys - - 416 

Sect. II. Titanium ------ 419 

Oxide, titanic acid, bisulphuret, bichloride, bifluo- 

ride, sulphate ----- 420 

Sect. III. Chromium ----- 421 

Oxide, sesquisulphuret, sesquichloride, sulphate, 

chrome alum, oxalate, chrome iron, chromic acid ib. 

Chromates: yellow chromates, red chromate of pot- 
ash, Peligot's salt, chromates of lead, silver, mag- 
nesia ------ 424 

Chlorochromic acid, terfluoride of chromium - 425 

Sect. IV. Vanadium ------ ib. 

Oxide, peroxide, vanadic acid - 426 

Sect. V. Tungsten and molybdenum ib. 

Tungstic oxide, tungstic acid, sulphurets, chlorides 427 

Molybdenum, molybdous oxide, molybdic oxide, 

molydic acid, sulphurets, chlorides - - 428 

Sect. VI. Tellurium - .... 430 

Tellurous acids, telluric acids, telluretted hydrogen, 

sulphurets, chlorides ib. 



ORDER VI. 

Metals isomorphous with phosphorus. 

Sect. I. Arsenic ------ 433 

Arsenious acid, arsenic acid, sulphurets of arsenic, 

chlorides, arsenietted hydrogen - - - ib. 

Testing for arsenic - . - 436 



XVI CONTENTS. 

Page 
Sect. II. Antimony - - - - 439 

Oxide, sulphuret, chloride, tartrate of potash and 

antimony, antimonious acid, antimonic acid, &c. 440 



ORDER VII. 

Metals not included in the foregoing classes, of which the oxides are not 
reduced by heat alone. 

Uranium ------ 443 

Cerium - - - - - - 444 

Lantanum - - - ib. 

Didymium - 445 

Tantalum ----- ib. 



ORDER VIII, 

Metals of which the oxides are reduced to the metallic state by heat 
(noble metals.) 

Sect. I. Mercury - - - - - - 447 

Suboxide, subchloride (calomel,) &c. - - 448 

Oxide (red oxide,) sulphuret, chloride (corrosive 

sublimate,) <S$c. - - - - - 451 

Sect. H. Silver ------ 458 

Oxide, chloride, salts, &c. - 460 

Sect. III. Gold ------ 464 

Oxides, chlorides, purple of Cassius, &c. - - ib. 



ORDER IX. 

Metals in native platinum. 

Sect. I. Platinum - 467 

Oxides, chlorides, salts of Gros, &c. - - 469 

Sect. II. Palladium - - - - - 471 

Oxides, chlorides, cyanide, &c. - - - 472 

Sect. III. Iridium ------ 473 

Osmium ------ 474 

Sect. IV. Rhodium ------ 476 



CONTENTS. XV11 



PART III. 

ORGANIC CHEMISTRY. 
CHAPTER I. 

Page 

Preliminary observations - 478 

Organic analysis ----- 479 
Modifications of organic compounds produced by 

artificial processes - 485 

Distillation with an alkali - - - - 486 

Dry distillation ----- 487 

Action of oxygen — eremacausis - 488 
Action of chlorine, its substitution for hydrogen, 

chemical types ----- 490 
Transformations of organic substances, action of fer- 
ments ■ - - - - - 494 
Molecular theory of organic compounds - - 497 

CHAPTER II. 



Amylaceous and saccharine substances. 

Sect. I. Starch, amylin, amid in, starch granules of Jacque- 

lain, iodide of starch - 504 
Dextrin, British gum, diastase, brewing, gluten, 

inulin, lichen starch - 507 

Cane-sugar, or ordinary sugar - 510 

Caramel, metacetone, saccharic acid - - 512 

Grape sugar, starch and diabetic sugar - - 513 

Sulphosaccharic acid, sacchulmine, glucic and me- 

lassic acids - - - - - 514 

Sugar of milk or lactine, mucic acid - - 515 
Mushroom sugar, insipid sugar of Thenard, liquor- 
ice sugar - - - - - 516 

Manna sugar or mannite ib. 

Gum, lignin, suberic acid - 517 

Sect. II. Products of the fermentation of sugar - - 518 

Ethyl series of compounds - - - ib. 

Alcohol ------ ib. 

Ether ------ 520 

Chloride of ethyl, or hydrochloric ether - •• 522 

Mercaptan, &c. ----- 523 

Salts of oxide of ethyl - 524 
2* 



■XV111 CONTENTS. 

Page 

Sulphovinic acid - - - - 524 

Theory of etherification - 525 
Nitrous ether, oxalic ether, oxamethane, uretbane,. 

&c. ------ 527 

Transformations of bodies containing ethyl, sweet 

oil of wine, ethionic and isethionic acids, &c. - 530 

Sect. Ill; Acetyl series of compounds - 531 

Aldehyde, roetaldehyae, acetal, &c. *. - ib. 

Aldehydic acid - - - - - 532 

Acetic acid, acetic ether, acetates, &c. - - 533 

Sect. IV. Products of the action of chlorine, bromine and, 

iodine upon ethyl, acetyl and their compounds 535 
Oxichloride of ethyl, oxisulphuret, chloroxalic ether, 

&c. - - - - - -. ib. 

Chloral, hydrate of chloral, insoluble chloral - 536 

Chloracetic acid, bromal, iodal, &c» - - 537 

Sect. V. Congeners of alcohol of an uncertain constitution - 538 
Oleflant gas, chloride of acetyl, chloroplatinate of 

chloride of acetyl, &c. - ib. 
Sect. VI. Products of the action of heat upon, the acetic acid 

of the acetates.. -.. - - 540 

Acetone ------ ib. 

Mesitylene, oxide of mesityle, &c. - - 541 

Sect. VII. Arsenical compounds derived from acetyl - ' - 543 

Cacodyl ----- - ib. 

Alcarsin, alcargen, &c. --'-'-., - u 544 

Sect. VIII. Relation between the ethyl and ammonium series - 546 

Sect. IX. Lactic and viscous fermentations - 550 

Lactic acid -.-,... 55 1 

Sect. X. Oil of grain and potato spirits, or fousel oil -, 552 

Amyl series of compounds - ib. 

Chloride of amyl, &c. - 554 

Valeric or valerianic acid, &c. - 555 

Sect. XI. Ethereal oilof wine — 03nanthic ether - - 556 

(Enanthic acid- - - 557 



CHAPTER lit 

Products of the dry distillation of ivood. 

Sect. I. Methyl series of compounds - 558 

Oxide of methyl,, or. methylic ether,, wood-spirit - ib. 

Chloride of methyl, iodide, sulphuret, &c. - - 559 

Sulphate of oxide of methyl, nitrate, &c. - - 560 

Products of the decomposition of methyl' - - 562 

Sect. II. Formyl series of compounds ib. 

Formic acid, and formiates - 563 

Chlorides of formyl, chloroform, bromoform, &c. - 566 

Sect. III. Other products: xylite, mesiten, xylitic acid, mesite, 

&c. - - - - - - 569 

Sect. IV. Products contained in wood tar: paraffin, eupion, 

creosote, picamar, pittacal, &c. - - - 570 



CONTENTS. XIX 

Page 

In coal tar: naphtaline, compounds of naphtaline, &c. 572 

Sect. V. Bitumen: naphtha, naphtene, &c. - 575 



CHAPTER IV. 

Amygdalin and the bodies derived from its decomposition. 

Sect. I. Amygdalin --...-- 576 

Amygdalic acid ----- 577 

Sect. II. Benzoyl series of compounds ib. 

Benzoic acid and benzoates _ _ _ j D# 

Essence (volatile oil) of bitter almonds - - 579 

Chloride of benzoyl, &e. - ib. 

Hippuric acid ----- 58O 

Products of the decomposition of benzoyl com- 
pounds, hyposulphobenzoic acid, nitrobenzoic 

acid, &c. _---- 581 

Benzole or benzin and its compounds - - 583 

Hydrobenzamide, &c. - 584 

Benzoine, benzile, benzilic acid, &c. - - 585 

Synaptase ------. 586 

CHAPTER V. 

Essence of cinnamon and bodies derived from it -. 588 

Cinnamyl series of compounds ; oil, cinnamic acid, &c. ib. 



CHAPTER VI. 



Salicin and bodies obtained from its decomposition, 

Salicin, &c. - 590 

Salicyl series; salicylous acid, salicylimide, salicylic 

acid, &c. ------ 591 

Oil of Gaultheria and bodies drivedfrom it - - 594 

Phloridzin and the bodies derived from it - 595 

Glyceryl, &c. - - - - 596 

Ethal and the cetyl series -- -- -- - 597 



CHAPTER VII. 
Other indifferent substances -. 599 

Class L Ordinary constituents of plants. 

Sect. I. Pectin, pectic acid ----- 599 

Sect. II. Volatile or essential oils, and their resins - - 600 



XX CONTENTS. 

Page 

A. Essential oils containing no oxygen ; oil of turpen- 
tine ------ 602 

Colophony or resin of turpentine - 604 

Oil of lemons, copaiba, &c. - 605 

B. Essential oils containing oxygen; oil of berga- 

motte, anise, cloves, cummin, peppermint, cedar, &c. 606 

Camphor, camphoric acid, &c. - - - 610 

C. Essential oils containing sulphur ; oil of mustard, 

&c. 611 

Nicotianine, helenine, caoutchouc, &c. - - 612 

Resins, amber, resinous varnishes - - - 613 

Gum resins, chlorophyl - - - - 615 

Class II. Constituents of particular plants or families of plants. 

Sect. I. Piperin, asparagin, santonin, esculin, picrotoxin, an- 

thiarin, caffein, coumarin, &c. - - - 616 

Vegetable albumen and legumin - - - 618 

Sect. II. Neutral colouring matters - - - - 619 

Indigo, white or reduced indigo, sulphindylic, anilic 
and picric acids, chlorisatin, aniline, «fcc. - - ib. 

Colouring matters of archil, litmus and cudbear; orcin, 

orceine, &c. ----- 623 

Colouring matters of madder ; alizarin, &c., (princi- 
ples of dyeing) ----- 626 

Carthamin, hematoxylin, brezilin, berberin, quercitrin 628 



CHAPTER VIII. 

Organic acids - - - - - 631 

Sect. I. Acids supposed to contain carbonic oxide - - ib. 

Oxalic acid and oxalates ib. 

Rhodizonic and croconic acids - 632 

Melliticacid ----- 633 

Sect. II. Meconic acid and its congeners, comenic and pyro- 

meconic acids - - - - - 634 

Sect. m. Tannic acid and bodies allied to it - - - 635 

Gallic acid, pyrogallic and ellagic acids, &c - - 637 

Sect. IV. Citric acid, and the products of its decomposition, 

aconitic, itaconic and citraconic acids - - 639 

Sect. V. Tartaric acid and the products of its decomposition, 

tartrelic, tartralic, pyrotartaric acids - - 640 

Paratartaric (racemic acid) - 643 

Sect. VI. Malic acid ; maleic and fumaric acids - - 644 

Sect. VII. Kinic or quinic acid - 645 

Sect. VIII. Volatile acids of butter; veratric acid, &c. - - 646 

Sect. IX. Oily acids of butter of cocoa, nutmegs, and palm oil - 648 

Margaric and stearic acids - 649 

Distillation of margaric and stearic acids; margarone 651 

Action of nitric acid on margaric and stearic acids, 

suberic and succinic acids - 652 



CONTENTS. XXI 

Page 
Sect. X. Oleic acid and acids related to it ; sebacic and elaidic 

acids - - - - - -'" 653 

Acids of castor oil _ _ . 655 

Sulpholeic, sulphomargaric acids, &c. - 1 - ib. 

Acroleine ------ 656 



CHAPTER IX. 

Vegeto -alkalies ----- 656 

Sect. I. Morphine and the other bases in opium; narcotine, 

codeine, thebaine, narceine - 660 

Sect. II. Quinine and cinchonine - 662 

Strychnine and brucine - 663 

Sect. III. Veratrine ------ 664 

Sect. IV. Conicine, atropine, nicotine, &c. ib. 



CHAPTER X. 

Cyanogen and its compounds - 665 

Sect. I. Formation of cyanogen - - - - ib. 

Sect. II. Hydrocyanic acid, cyanides - 667 
Double cyanides of iron, cobalt, chromium, plati- 
num, &c. __--- 669 
Sect. III. Compounds of cyanogen with oxygen; cyanic acid, 

urea ------ 670 

Fulminic acid - 673 

Cyanuric acid, &c. ib. 
Sect. IV. Sulphocyanogen, metasulphocyanogen, mellon, cya- 
nilic acid, melam, melamine, ammeline, ammelide, 

&c. - 674 

Sect. V. Uric acid and the products of its decomposition - 677 

Uric acid ------ ib. 

Allantoin ----- - 678 

Alloxan; alloxanic, parabanic, oxaluric acids, &c. - ib. 

Alloxantin ----- 680 

Murexide ------ 681 

Murexan ------ 682 



CHAPTER XI. 

Sect. I. Organic processes of plants and animals - - 683 

Food of plants ----- ib. 

Food of animals - - - - - 685 

Respiration ib. 

Animal heat - - - - - 687 

Digestion ------ ib. 

Sect. II. Modifications of protein - - - - 

Albumen ------ 690 

Fibrin - - - - - - 691 

Protein, xanthoproteic acid, leucin, &c. - - 692 



XXII CONTENTS. 

Page 

Casein ------ 693 

Sect. III. Pepsin - - - - - 695 

Hematosin ----- 697 

Globulin 698 

Gelatin, tanno- gelatin, leather, &c. - - ib. 

Chondrin, &c. 700 

Horny matter, &c. - - - - 701 

Sect. IV. Saliva, gastric juice, pancreatic juice - - 703 

Bile and biliary concretions, &c. - - - 704 

Cholesterin ..... 706 

Chyle - - .... ib. 

Excrements - - - - - - 707 

Sect. V. Lymph, mucus, pus ... - ib. 

Sect. VI. Blood, milk ----- 708 

Urine ------ 709 

Urinary concretions - - - - 710 

Sect. VII. Solid parts of animals - - - - 711 

Bones, teeth, skin, muscle, fat - - ^ ib. 

Brain and nerves - t - - - 713 

The eye ------ ib. 



APPENDIX. 

Tab. I, For the conversion of degrees centigrade into degrees 

Fahrenheit - - - - - 715 

Elastic force of vapour at different temperatures - 718 

Density of sulphuric acid - - - - 720 

Density of nitric acid - 721 

Density of alcohol - - - ■ - 722 

Beaume's hydrometer ib. 

For reference in qualitative analysis; 1. Gases, 2. 

Acids, 3. Alkalies and earths, 4. Metallic oxides - 723 

Selected atomic weights, with their logarjthjns - 726 

Electro-chemical distribution of the elements - 728 

General Index; - 729 



Tab 


.11. 


Tab. 


III. 


Tab. IV. 


Tai 


1. V. 


Tab 


VI. 


Tab. 


VII. 


Tab. VIII. 


Tab. 


IX. 



LIST OF WOOD CUTS. 



Pags 



Figa. 
1. Dulong and Petit*s instru- 
ment for expansion of 
liquids, . . . .29 
2, 3, 4, 5. Expansion of water illus- 
trated, - . . .30 
6, 7. Thermometers, . . .33 

8. Mode of making, . . 34 

9. Scales compared, . . 36 

10. Daniel's pyrometer, . . 37 

11. Self-registering thermometers 38 

12. Vibration between masses of 

different temperatures, . 42 I 

13. Heating of liquids, . . 42 

14. Circulation in fluid by calo- 

ric, . . . .43 

15. Radiation of caloric, . . 44 

16. Reflection of caloric, . . 44 

17. Melloni's instrument for 

measuring caloric trans* 
mitted through media, . 46 

18. Elastic force of steam, . 58 

19. Expansive force of water 

when converted into 
steam, . . . .61 

20. Expansive force of steam, . 62 

21. Wagon boiler, . . .62 

22. Cylinder boiler, . . .62 

23. Boiler for locomotives, . 63 

24. Distillation, ... 63 
25, 26. Liebig's condensing tube, . 64 

27. Elastic force of different va- 

pours, . . . .65 

28. Wollaston's Cryophorus, . 66 

29. Condensation of gases, . 68 

30. Diffusion of gases, . . 70 
31,32. „ . 72 

33. Wet bulb thermometer, . 76 

34. Daniel's hygrometer, . 77 

35. Drying chamber, . . 79 

36. Drying tube, ... 79 

37. Refraction of light, . . 82 

38. Decomposition of light, . 83 

39. Spectra 84 

40. Simple voltaic circle, . . 157 

41. illustrating decom- 
position, . . . 157 

42. Active and decomposing 

cells, i i i 158 



Figs. 
43, 44. Polarity, 
45, 46, 47. 
48, 49. 
50. — 



Page 
159 
160 
161 



of simple voltaic cir- 
cle 163 

51. of impure zinc, .165 

52. of compound voltaic 

circle, . . . .165 

53, 54. Ditto 166 

55, 56. Ditto. . 167 

57, 58. Compound circles, . . 168 

59. Ditto 170 

60. Ditto 171 

61. Simple thermoelectric cir- 

cle, . . . .179 

62. Compound thermo-electric 

circle, . . . .179 
63, 64. Daniel's constant battery, . 181 

65. Bird's battery and decom- 

posing cell, . . , 182 

66. Voltameter, . . .183 

67. Galvanometer, . . . 184 

68. Preparation of oxygen from 

red oxide of mercury, . 186 

69. from black oxide of 

manganese, . . . 187 

70. Mode of transferring gases, 188 

71. Preparation of oxygen from 

chlorate of potash, . . 188 

72. hydrogen from steam, 194 

73. — — - from water, by a 

metal and acid, . . 195 

74. nitrogen from atmo- 
spheric air, . . . 203 

75. Ure's endiometer, . . 208 

76. Preparation of nitrous oxide, 21 1 

77. Primitive form of diamond, 221 

78. Impregnation of water with 

sulphurous acid, . . 235 

79. Sulphuric acid chamber, . 237 

80. Preparation of chlorine, .257 
81, 82. Ditto 258 

83. Manufacturer's rriethodj . 259 

84. Evolution of chlorous acid, 

and combustion by, un- 
der water, . . . 269 

85. Preparation of iodine, . 276 

86. __ of fluosilicic acid, . 285 



XXIV 



LIST OF WOOD CUTS. 



Figs. 

87. 



89. 
90. 
91. 
92. 

93. 

94. 
95. 

96. 
97. 
98. 
99. 

100. 

101. 
102, 103. 

104. 
105. 
]06. 
106. 
107. 

108. 

109. 

110,111. 



Page 
Preparation of phosphuret- 

ted hydrogen, . . 298 

Davy's safety lamp, . . 300 
Structure of flame, . . 302 
Apparatus for potassium, . 313 
Section of receiver, „ . 314 
Crystal of ferrocyanide of 
potassium, . . . 318 

of bicarbonate of 

potash, . . , . 321 

of sulphate of potash, 321 

of bisulphate of pot- 
ash 322 

of nitrate of potash, 323 

of carbonate of soda, 329 

Alkalimeters, . . .330 
Sections of reverberatory 

furnace, . . . 333 

Crystal of sulphate of mag- 

nesia, .... 356 
Crystal of alum, . . 362 

Rotal action of chemical af- 
finity, . . . .380 
Blast furnace, . . . 382 
Crystal of sulphate of iron, . 389 

of sulphate of zinc, . 400 

■ of acetate of lead, . 412 

Testing for arsenic by sul- 
phuretted hydrogen, . 436 
Reduction tube of Berzelius, 437 
Common reduction tubes, . 438 
Marsh's apparatus, . . 438 



Figs. Page 

112. Crystal of tartrate of potash 

and antimony, . . 441 

U3 # of calomel, . .449 

114. ■ of corrosive subli- 

mate, .... 456 
115. of nitrate of silver, . 462 

116. Combustion tube, for orga- 

nic analysis, . . . 479 

117. Method of drying mix. 

ture 480 

118. Furnace for combustion, . 480 

119. Tube supporter and front of 

furnace, . . . 480 

120. Furnace arranged with chlo- 

ride of calcium tube and 
potash bulbs, . . . 481 

121. Suction tube, . . .481 

122. Screen, . . . .481 

123. Ditto 482 

124. Furnace, &c. arranged as at 

the completion of the 
combustion, . . . 482 

125. Mode of combustion for esti- 

mation of nitrogen, .483 

126. Vinegar generator, . . 533 

127. Displacement apparatus for 

tannin, .... 636 

128. Crystal of citric acid, .639 
129,130. of tartaric acid, .641 

131. of tartrate of potassa, 642 

132, 133. of tartrate of soda 

and potassa, . . . 642 



ELEMENTS 



CHEMISTRY, 



CHAPTER I. 



HEAT. 

The objects of the material world are altered in their properties by heat in 
a very remarkable manner. The conversion of ice into water, and of water 
into vapour, by the application of heat, affords a familiar illustration of the ef- 
fect of this agent in changing the condition of bodies. All other material 
substances are equally under its influence; and it gives rise to numerous and 
varied phenomena, demanding the attention of the chemical inquirer. 

Heat is very readily communicated from one body to another; so that when 
hot and cold bodies are placed near each other, they speedily attain the same 
temperature. The obvious transference of heat in such circumstances, im- 
presses the idea that it possesses a substantial existence, and is not merely a 
quality of bodies, like colour or weight; and when thus considered as a mate- 
rial substance, it has received the name caloric. It would be injudicious, how- 
ever, to enter at present into any speculation on the nature of heat; it is suffi- 
cient to remark that it differs from matter as usually conceived, in several 
respects. Our knowledge of heat is limited to the different effects which it pro- 
duces upon bodies, and the mode of its transmission; and these subjects may 
be considered without reference to any theory of the nature of this agent. 

The subject of heat will be treated of under the following heads: — 

1. Expansion, the most general effect of heat and the Thermometer. 

2. Specific Heat. 

3. The communication of heat by Conduction and Radiation. 

4. Liquefaction, as an effect of heat. 

5. Vaporization, or the gaseous state, as an effect of heat. 

6. Speculative notions which have been entertained respecting the Nature 
of heat. 

EXPANSION AND THE THERMOMETER. 

All bodies in nature, solids, liquids, or gases, suffer a temporary increase of 
dimension when heated, and contract again into their original volume on 
cooling. 
3 



26 EXPANSION OF SOLIDS. 

1. Expansion of solids. The expansion of solid bodies, such as the 
metals is by no means considerable, but may readily be made sensible. A bar 
of iron which fits easily, when cold, into a gauge, will be found, on heating it 
to redness, to have increased sensibly both in length and thickness. The ex- 
pansion and contraction of metals indeed, and the immense force with which 
these changes take place, are matters of familiar observation, and are often 
made available in the arts. The iron hoops of carriage wheels, for instance, 
are applied to the frame while they are red hot, and in a state of expansion, 
and being then suddenly cooled by dashing water upon them, they contract and 
bind the wood work of the wheel with great force. The expansion of solids, 
however, is very small, and requires nice measurement to ascertain its amount. 
The expansion in length only has generally been determined, but it must always 
be remembered, that the body expands also in its other dimensions, in an equal 
proportion. The first general fact observable is, that the amount of dilatation 
by heat is different in different bodies. No two solids expand alike. The 
metals expand most, and their rates of expansion are best known. Rods of 
the under-mentioned substances, on being heated from the freezing to the boil- 
ing point of water, elongate as follows: 

Lead . . . 1 on 351 Pure Gold . 1 on 682 

Silver 1 ,, 524 Iron Wire . 1 „ 812 

Copper . . . 1 ,, 581 Platinum. . 1 ,, 1167 

Brass . . . 1 „ 584 Flint Glass . 1 „ 1248 

This is the increase which these bodies sustain in length. Their increase 
in general bulk is about three times greater. Thus, if glass elongates 1 part 
in 1248 from the freezing to the boiling point of water, it will dilate in cubic 
capacity 3 parts in 1248 or 1 part in 416. The expanded bodies return to 
their original dimensions on cooling. Wood does not expand much in length; 
hence it is occasionally used as a pendulum rod. For the same reason a slip 
of marble has lately been employed for that purpose, in constructing the clock 
of the Royal Society of Edinburgh. * Flint glass expands by the table joxf 
part, while the metal platinum expands very little more, ( Tf Vy) Hence the 
possibility of cementing glass and platinum together, as is done in many che- 
mical instruments. Other metals pushed through the glass when it is red hot 
and soft, shrink afterwards so much more than the glass on cooling, as to 
separate from it, and become loose. Lead is the most expansible of the 
metals; it expands between three and four times more than platinum from the 
same heat. 

By far the most important discovery in a theoretical point of view, that has 
been made on the subject of the dilatation of solids by heat, is the observation 
of Professor Mitscheflich of Berlin, that the angles of some crystals are af- 
fected by changes of temperature. This proves that some solids in the crys- 
talline form do not expand uniformly, but more in one direction than in ano- 
ther. Indeed, Mitscherlich has shown that while a crystal is expanding in 
length by heat, it may actually be contracting at the same time in another 
dimension. An angle of rhomboidai calcareous spar alters eight and a half 
minutes of a degree between the freezing and boiling points of water. But 
this unequal expansion does not occur in crystals of which all the sides and 
angles are alike, as the cube, the regular octohedron, the rhomboidai dodeca- 
hedron. In investigating the laws of expansion among solids, it is advisable, 
therefore, to make choice of crystallized bodies. For, in a substance not regu- 
larly crystallized, the expansion of different specimens may not be precisely 
the same, as the internal structure may be different. Hence, the expansions 
of the same substance, as given by different experimenters, do not always ex- 
actly correspond. The same glass has been observed to dilate more when in 



EXPANSION OF SOLIDS. . 27 

the form of a solid rod, than in that of a tube; and the numerous experiments 
on uncrystallized bodies, which we possess, have afforded no ground for gene- 
ral deductions. 

It has been farther observed, that the same solid is more expansible at high 
than at low temperatures, although the increase in the rate of expansion is in 
general not considerable. Thus, if we mark the progress of the dilatation of 
a bar of iron under a graduated heat, we find that the increase in dimension is 
greater for one degree of heat near the boiling point of water than for one de- 
gree near its freezing point. Solids are observed to expand at an accelerated 
rate, in particular, when heated up to near their fusing points. The cohesion 
or attraction which subsists between the particles of a solid is supposed to resist 
the expansive power of heat. But many solids become less tenacious, or 
soften before melting, which may account for their increasing expansibility. 
Platinum is the most uniform in its expansions of the metals. 

Such changes in bulk, from variations in temperature, take place with irre- 
sistible force. This was well illustrated in an experiment, which was suc- 
cessfully made upon a gallery in the Museum of Arts and Manufactures in 
Paris, in order to preserve it. The opposite walls of this edifice were bulging 
outwards, from the pressure of the floors and roof, which endangered its sta- 
bility. By the directions of an ingenious mechanic, stout iron rods were laid 
across the building, with their extremities projecting through the opposite 
walls. The rods were then strongly heated by a number of lamps, and when 
in an expanded condition, a disc on either extremity of each rod was screwed 
firmly up against the external surface of the wall. On afterwards allowing 
the rods to cool, they contracted, and drew the walls to which they were at- 
tached somewhat nearer together. The process was several times repeated, 
till the walls were restored to a perpendicular position. 

The force of expansion always requires to be attended to in the arts, when 
iron is combined in any structure with less expansible materials. The cope- 
stones of walls are sometimes held together with clamps, or bars of iron: such 
bars, if of cast iron, which is brittle, often break on the first frost, from a ten- 
dency to contract more than the stone will permit; if of malleable iron, they 
generally crush the stone, and loosen themselves in their sockets. When 
cast iron pipes are employed to conduct hot air or steam through a factory, 
they are never allowed to abut against a wall or obstacle which they might in 
expanding overturn. 

A compound bar, made by soldering together two thin plates of copper and 
platinum, affords a good illustration of unequal expansion by heat. The cop- 
per plate, being much more expansible than platinum, the bar is bent upon the 
application of heat to it; and in such a manner, that the copper is on the out- 
side of the curve. It may easily be conceived, that by a proper attention to 
the expansions of the metals of which it is composed, a bar of this kind might 
be so constructed, that although it was heated and expanded, its extreme points 
should always remain at the same distance from each other, the lengthening 
being compensated for by the bending. The balance wheels of chronome- 
ters are preserved invariable in their diameters, at all temperatures, by a 
contrivance of this kind. It has also been applied to the construction of a 
thermometer of solid materials — that of Breguet. 

When hot water is suddenly poured upon a thick plate of glass, the upper 
surface is heated and expanded before the heat penetrates to the lower surface 
of the plate. There is here unequal expansion, as in the case of the slip of 
copper and platinum. The glass tends to bend, with the hot and expanded 
surface on the outside of the curve; but is broken from its want of flexibility. 
The occurrence of such fractures is best avoided by applying heat to glass 
vessels in a gradual manner, so as to occasion no great inequality of expan- 



28 . EXPANSION OF LIQUIDS. 

sion; or by using very thin vessels, through the substance of which heat is 
rapidly transmitted. 

This effect of heat on glass may, by a little address be turned to advantage. 
Watch glasses are cut out of a thin globe of glass, by conducting a crack in a 
proper direction, by means of an iron rod, or piece of tobacco pipe, heated to 
redness. Glass vessels damaged in the laboratory may often be divided in 
the same manner, and still made available for many useful purposes.* 

Both cast iron and glass are peculiarly liable to accidents from unequal ex- 
pansion, when in a state of flat plates. Plate glass indeed can never be heated 
without risk of its breaking. The flat iron plates placed across chimneys as 
dampers, are also very apt to split when they become hot, and much inconve- 
nience has often been experienced in manufactories from this cause. A slight 
curvature in their form has been found to protect them most effectually. 

Expansion of liquids. In liquids the expansive force of heat is little re- 
sisted by cohesive attraction, and is much more considerable than in solids. 
This fact is strikingly exhibited by filling the bulb and part of the stem of a 
common thermometer tube with a liquid, and applying heat to it. The liquid 
is seen immediately to mount in the tube. 

The first law in the case of liquids is that some expand much more consi- 
derably by heat than others. Thus, on being heated to the same extent, 
namely, from the freezing to the boiling point of water, 

Spirits of wine expand } that is, 9 measures become 10 

Fixed oils T V „ 12 „ 13 

Water ^-V* » 22 ' 76 " 23 - 76 

Mercury $l, T ,, 55.5 ,, 56.5 

Spirits of wine are, therefore, six times more expansible by heat than mer- 
cury is. The difference in the heat of the seasons affects sensibly the bulk of 
spirits. In the height of summer spirits will measure 5 per cent, more than in 
the depth of winter. 

The new liquids produced by the condensation of gases appear to be cha- 
racterized by an- extraordinary dilatability. M. Thiiorier has observed that 
fluid carbonic acid is more expansible by heat than air itself; heated by 32° 
to 86°, twenty volumes of this liquid increase to twenty-nine, which is a dila- 
tation fourt times greater than is produced in air, by the same change of tempe- 
rature.! Mr. Kemp has extended this observation to liquid sulphurous acid 
and cyanogen, which although not possessing the excessive dilatability of 
liquid carbonic acid, are still greatly more expansible than ordinary liquids. 
Sir D. Brewster had several years before discovered certain fluids in the 
minute cavaties of topaz and quartz, which seemed to bear no analogy to any 
other known liquid in their extraordinary dilatability. They do not appear to 
have been entirely liquefied gases, but probably were so in part.§ 

A singular correspondence has been observed, by M. Guy-Lussac, between 
two particular liquids — alcohol and sulphuret of carbon, in the amount of their 
expansion by heat; although each of these liquids has a particular temperature 
at which it boils — 

Alcohol at 173° 

Sulphuret of carbon at 116° 

* [When the stoppers of glass stoppered bottles become tight they may be frequently re- 
moved without fracture by carefully heating the neck of the bottle until it expands and 
the stopper becomes loose. R. B.] 

f [The experiments of Prof. Mitchel give the expansion as three times that of air. — Journ. 
Frank. Institute, vol. 20. R. B.] 

t Annales de Chimie et de Physique, t. 60, p. 427. 

§ Edinburgh Phil. Trans, vol. x. 1824. 



EXPANSION OF LIQUIDS. 



29 



still the ratios of expansion from the addition, and of contraction from the loss 
of heat, are found to be uniformly the same in the case of these two liquids, 
which are the only ones known to possess such a • relation. The number of 
liquids, however, the expansions of which, under different degrees of heat, 
have been examined, is exceedingly small; although comparative experiments 
may be made with much greater facility in regard to liquids than solids. 

The second law is, that liquids are progressively more expansible at higher 
than at lower temperatures. This is less the case with mercury, perhaps, 
than with any other liquid. The expansions of that liquid are, indeed, so uni- 
form, as to render it extremely proper for the construction of the thermometer. 
as will afterwards appear. The rate of expansion of mercury was deter- 
mined with extraordinary care by Dulong and Petit. 

From 1° to 100° centigrade, mercury expands 1 measure on 55*- 

,,100° ,,200° „ „ „ 1 „ 541 

„ 200° „ 300° „ „ „ 1 „ 53 

According to the same experimenters, the expansion of mercury, confined 
in glass tubes, is only 1 on 64.8. The dilatation of the glass causes the ca- 
pacity of the instrument to be enlarged, so that the whole expansion of the 
mercury is not indicated. 

The only mode in which the error introduced by the expansion of the 
enclosing vessels can be Fig. 1. 

avoided, in ascertaining the 
expansions of liquids, is 
that practised by Dulong 
and Petit; namely, heating 
the liquid in one limb of a 
syphon, (see Fig. 1.) and 
observing how high it rises 
above the level of the same 
liquid in the other limb, 
kept at a constant tempe- 
rature. The columns of 
course balance each other, and the shorter column of dense fluid supports a 
longer column of dilated fluid. All other modes of obtaining the absolute ex- 
pansions of liquids are fallacious. 

No progress has yet been made in discovering the law by which expansions 
of liquids are regulated; for the complicated mathematical formulas of Biot, 
Dr. Young, and others, are mere general expressions for these expansions, 
which proceed upon no ascertained physical principle. Some theory must 
be formed of the constitution of liquids, before we can hope to account for 
their expansions. 

Count Rumford ascertained the contraction of water for every 221°, in cool- 
ing from 212° to 32°. The results were as follows, 2000 measures of water 

contract — 
In cooling 




22i°, 



or 



from 



measures. 



18 
16.2 
13.8 
11.5 
9.3 
7.1 
3.9 
0.2 
The expansion of water by heat, is subject to a remarkable peculiarity 
which occasions it to be extremely irregular, and demands special notice. 

3* 



212° 


to 


1891 • 


189£ 


*» 


167 


167 


i» 


144» . 


144i 


,, 


122 


122 


,, 


991 . 


99} 


,, 


77 


77 


,, 


541 . 


541 


„ 


32 



30 



EXPANSION OF LIQUIDS. 



Fig. 2. 



This liquid, in a certain range of temperature, becomes an exception to the 
very general law that bodies expand by heat. When heat is applied to ice- 
cold water, or water at the temperature of 32°, this liquid, instead of expand- 
ing, contracts by every addition of heat, till its temperature rises to 40° at, or 
very near which temperature water is as dense as it can be. And, conversely, 
when water of the temperature of 40° is exposed to cold, it actually expands 
with the progress of the refrigeration. Water may, with caution, be cooled 
20 or 35 degrees below its freezing point, in the fluid form, and still continue 
to expand. It is curious that this liquid, in a glass bulb, 
expands as nearly as possible to the same amount, on 
each side of 42° when either heated or cooled the same 
number of degrees. Hence when cooled to 40° it rises to 
the same point in the stem as when heated to 44°; at 32° 
it stands at the same point as at 52°, and so on for diffe- 
rent temperatures, as illustrated in the graduation of the 
figure. The expansion of water by cold, under 40° is 
certainly not very great, being little more than one part in 
1000 at 32°; hence it was early suspected that it might be 
an illusion, from the contraction of the glass bulb, (in 
which the experiment was always made) forcing up the 
water in the stem. But all grounds of objection on this, 
score have been removed by the mode in which the ex- 
periment has subsequently been conducted, particularly in 
the admirable researches of Dr. Hope on this sub- 
ject. 

Dr. Hope carried a deep glass jar, filled with water of 
the temperature of 50°, into a very cold room; and having 
immersed two small thermometers in the water, one near 
the surface, and the other at the bottom of the jar, watched, their indications 
as the cooling proceeded. The thermometer above indicated a temperature 
higher bv several degrees than the thermometer below, till the temperature 



26 - 


- 58 


28 - 


- 56 


30 - 


- 54 


32 - 


- 52 


34 - 


- 50 


36 - 


-48 


38 - 


-46 


40 - 


-44 


42 -U 


-- -42 











Fig. 3. 

In cooling 
above 40 D . 



Fig. 4, 



Fig. 5. 

In cooling- 
below 40°. 






fell to 40°, that is, the chilled 
water fell as usual to the bot- 
tom of the jar, or became 
denser as it lost heat, as illus- 
trated in Fig. 3. At 40° the 
two thermometers were for 
some time steady, (Fig. 4.) 
but as the cooling proceeded 
beyond that point, the instru- 
ment in the higher situation 
indicated the lower tempera- 
ture (Fig. 5;) or the water 
now as it became colder, became lighter, and rose to the top. A better de- 
monstration of the fact in question could not be devised. 

Great pains have been taken by several philosophers to determine the exact 
temperature of this turning point, at which water possesses its maximum den- 
sity. Bv the recent elaborate experiment of Hallstrom, this point is 39°. 38. 
Sir C. Blagden and Mr. Gilpen had made it 39°. Dr. Hope had estimated it 
at 39|°. 

When salt is dissolved in water, the temperature of the maximum density 
becomes lower and lower, in proportion to the quantity of salt in solution, and 
sinking below the freezing point of the liquid, the anomaly disappears. This 
is the reason why the interesting fact we have been discussing cannot be ob- 
served in the case of sea water. 

There is a solid body which presents the only other known parallel case of 



EXPANSION OF GASES. 31 

progressive contraction by heat; this is Rose's fusible metal which is an 

alloy of 

2 parts by weight of Bismuth 
1 part ,, ., „ Lead 
1 „ ,, »j » Tin. 
A bar of this metal expands progressively, like other bodies, till it attains the 
temperature of 111 ; it then rapidly contracts by the continued addition ot 
heat, and at 156° attains its maximum density, occupying less space than it 
does at the freezing point of water. It afterwards progressively expands 
melting at 201°. It may be remarked, however, of this body, that it is a che- 
mical compound, of a kind in which a change of constitution is very likely to 
occur from a change in temperature; and that it cannot, therefore, be fairly 
compared with water. 

The dilatation which water undergoes below 40° has been supposed to be 
connected with its sudden increase of volume in freezing, for ice is specifi- 
cally lighter than water, in the proportion of 92 to 100. The water, it is said, 
may begin to pass partially into the solid form at 40°, although the change is 
not complete till the temperature sinks to 32°. But such an assumption is 
altogether gratuitous, and improbable in the extreme. 

The extraordinary irregularity in the dilatation of water by heat is not only 
curious in itself, but also of the utmost consequence in the economy of nature. 
When the cold season sets in, the surface of our rivers and lakes is cooled by 
the contact of the cold air and other causes. The superficial water so cooled, 
sinks and gives place to warmer water from below, which chilled in its turn 
sinks in like manner. The progress of cooling in the lake goes on with con- 
siderable rapidity, so long as the cold water descends and exposes that not 
hitherto cooled. But this circulation, which accelerates the cooling of a mass 
of water in so extraordinary a degree, ceases entirely when the whole water 
has been cooled down to the temperature of 40° which is still 8 degrees above 
the freezing point. Thereafter the chilled surface water expands as it loses its 
heat, and remains on the top, from its lightness, while the cold is very imper- 
fectly propagated downwards. The surface in the end freezes, and the ice 
may thicken, but at the depth of a few feet, the temperature is not under 40°, 
which is high when compared with that frequently experienced, even in this 
climate during winter. 

If water continued to become heavier, until it arrived at the freezing tempe- 
rature, the whole of it would be cooled to that point before ice began to be 
formed; and the consequence would be. that the whole body of water would 
rapidly be converted into ice, to the destruction of every being that inhabits it. 
Our warmest summers would make but little impression upon such masses of 
ice; and the cheerful climate which we at present enjoy, would be less com- 
fortable than the frozen regions of the pole. Upon such delicate and beauti- 
ful adjustments, do the order and harmony of the universe depend. 

Expansion of Gases. The expansion by heat in the different forms of 
matter is exceedingly various. 

By being heated from 32° to 212°. 

1000 cubic inches of iron become 1004 
1000 „ water „ 1045 

1000 „ air „ 1375 

Gases are, therefore, more expansible by heat than matter in the other two 
conditions of liquid and solid. The reason is, that the particles of air or gas, 
far from being under the influence of cohesive attraction, like solids or liquids, 
are actuated by a powerful repulsion for each other. The addition of heat 
mightily enhances this repulsive tendency, and causes great dilatation. 

The rate of the expansion of air and gases from increase of temperature, 



32 EXPANSION OF FASES. 

was involved in considerable uncertainty till a recent period. This arose from 
the neglect of the early experimenters to dry the air of gas upon which they 
operated. The presence of a little water by rising in the state of steam into 
the gas, on the application of heat, occasioned great and irregular expansions. 
But in 1801, the law of the dilatation of gases was discovered by M. Guy- 
Lussac, of Paris, and by our countryman, Dr. Dalton, independently of each 
other. By keeping the gases experimented upon dry, these philosophers were 
enabled to discover that all gases experience the same increase in volume by 
the application of the same degree of heat. 

Dr. Dalton confined a small portion of dry air over mercury in a graduated 
tube. He marked the quantity by the scale, and the temperature by the ther- 
mometer. He then placed the whole in circumstances where it was uniformly 
heated up to a certain temperature, and observed the expansion. Guy-Lussac's 
apparatus was more complicated, but calculated to give very precise results. He 
found that 1000 volumes of air, on being heated from 32° to 212°, become 
1375, which agreed very closely with the result of Dr. Dalton. Mr. James 
Crichton, of Glasgow, has lately confirmed this determination, finding that 
1000 volumes of air become 1374.8. 

It follows, consequently, that air at the freezing point expands ^th part 
of its bulk for every added degree of heat on Fahrenheit's scale : that is — 

480 cubic inches at 32° become 

481 „ 33° 

482 „ 34, &c. 

increasing one cubic inch for every degree. A contraction of one cubic inch 
occurs for every degree below 32°. 

480 cubic inches at 32° become 

479 „ 31° 

478 „ 30° 

477 „ 29°, &c. 

We can easily deduce, from this law, the expansion which a certain volume 
of gas, at a given temperature will undergo, by heating it up to any particular 
temperature; or the contraction that will result from cooling. Air, of the 
temperature of freezing water, has its volume doubled when heated 480 de- 
grees, and when heated 960 degrees, or twice as intensely, its volume is 
trebled, which is the effect of a low red heat. 

Hydrogen gas, steam, and the vapour of sulphuric ether were found to ex- 
pand in the same proportion .as air. It has hence been concluded that the rate 
of expansion is the same in all gaseous fluids. It is to be observed also, that 
in the same air or gas, the rate of expansion continues uniform at all tempera- 
tures. 

[The recent experiments of Rudberg, Magnus and Regnault determine the amount of ex- 
pansion under the pressure of the atmosphere to be less than above stated. The results at 
which they arrived for atmo?pheric air when heated from 32° F. to 212° are as follows : 
10.000 cubic inches become 13.646 Rudberg.* 
10.000 „ „ 13:667 Magnus.t 

1C.000 „ „ 13.665 Regnault.t 

From which it follows that, for every degree on Fahrenheit's scale air expands ? 1^ (Rud- 
berg) ^-g (Magnus and Regnault,) of the bulk which it occupies at 32°. Magnus and 
Regnault also find that the rate of expansion is not precisely the same for all gases, the 
difference being greater in the gases which are condensible by pressure. This dissimilarity 
in the rate of expansion increases with the pressure to which the gases are subjected, 
more especially in the condensible gases as they approach their point of liquefaction. 

R. B.] 

* Ann. de Poggendorf, t. 41, 44. t Ann. de Chim. et Phys. 3»ne Ser. t. 4. 

♦ Ann. de Chiio. et Phys. 3me Ser. t. 4, 5. 



THE THERMOMETER, 



33 



THE THERMOMETER. 



o 



§ 




An instrument for indicating variations in the intensity of heat, or degrees 
of temperature, by their effect in expanding some body, was invented more 
than two centuries ago, and has received successive improvements. 

The expansions of solids are too minute to be easily measured, and cannot, 
therefore, be conveniently applied to mark degrees of heat. Air and gases, on 
the other hand, are so much dilated by a slight increase of heat, that they are 
not calculated for ordinary purposes.* The first thermometer constructed, 
however, that of Sanctorio, was an air one. A glass tube, Fig. 6. Fia. 7. 
open at one end, with a bulb blown upon the other, (Fig. 
6.). was slightly heated, so as to expel a portion of the air 
from it, and then the open end of the tube was dipped 
under the surface of a coloured fluid, which was allowed 
to rise into the tube, as the air cooled and contracted. 
When heat, the heat of the hand for instance, is applied 
to the bulb, the air in it is expanded, and depresses the 
column of coloured fluid in the tube. A useful modifi- 
cation of the air thermometer, for researches of great 
delicacy, was contrived by Sir John Leslie, under the 
name of the Differential thermometer. In this instrument, 
two close bulbs are -connected by a syphon containing a 
coloured liquid, (Fig. 7.) If both bulbs be equally heated, 
the air in each is equally expanded, and the liquid be- 
tween them remains stationary. But if the upper bulb 
only be heated, then the air in that bulb is expanded, and the column of liquid 
depressed. It is, therefore, the difference of temperature between the two 
bulbs which is indicated. 

But liquids fortunately are intermediate in their expansions between solids 
and gases, and when contained in a glass vessel of a proper form, the changes 
of bulk which they undergo can be indicated to any degree of precision. 

A hollow glass stem or tube is selected, the caliber or bore of which may be 
of any convenient size, but must be uniform, or not wider at one place than 
another. Tubes of very narrow bore, and which are called capillary, the bore 
being like a hair in magnitude, are now alone employed. Such tubes are made 
by rapidly drawing out a hollow mass of glass while soft and ductile under the 
influence of heat. The central cavity still continues, becoming the bore of 
the tube, and would not cease to exist although the tube were drawn out into 
the finest thread. From the mode in which capillary tubes are made, their 
equality of bore and suitableness for thermometers, cannot always be depended 
upon. The bore is frequently conical, or wider at one end than at the other. 
It is tested by drawing up into the tube a little mercury, as much as fills a few 
lines of the cavity. The little column is then moved progressively along the 
tube, and its length accurately measured, at every stage, by a pair of com- 
passes. The column will measure the same in every part of the tube, pro- 
vided the bore does not alter. Not more than one-sixth part of the tubes made 
are found to possess this requisite. 

Satisfied with the regularity of the bore, the thermometer-maker softens one 



* [Being influenced by the pressure of the atmosphere the indications will vary with this 
pressure. R. B.] 




34 THE THERMOMETER. 

extremity of the tube, and blows a ball upon it. This is not done by the 
mouth, which would moisten the interior, by introducing watery vapour, but 
by means of an elastic bag of caoutchouc, which is fitted to the open end of 
the tube. He then marks off the length which the thermometer ought to have, 
and above that point expands the tube into a second bulb a little larger than 
Fig. 8. the first. It has been the form of 

Figure 8. After cooling, the open 
extremity of the tube is plunged 
into distilled and well-boiled mer- 
cury, and one of the bulbs heated 
so as to expel air from it. During 
the cooling, the mercury is drawn 
up and rises into the ball a. It is 
made to pass from thence into, the 
^ ball b, by turning the instrument, 

so that b is undermost, and then expelling the air from that bulb by applying 
heat to it, after which the mercury descends from the effect of cooling. The 
ball 6, being entirely filled with mercury, and a portion left in a, the tube is 
supported by an iron wire, as represented in the figure, over a charcoal fire, 
where it is heated throughout its whole length, so as to boil the mercury, the 
vapour of which drives out all the air and. humidity, and the balls contain at 
the end nothing but the metal and its vapour. The open end of the tube, 
which must not be too hot, is then touched with sealing wax, which is drawn 
into the tube on melting, and solidifies there on protecting that end of the tube 
from the heat. That being done, the thermometer is immediately withdrawn 
from the fire, and being held with the end sealed with wax uppermost, during 
the cooling the ball 6, and the portion of the tube below the ball «, are filled 
with mercury. After cooling, the instrument is inclined a little, and by warm- 
ing the lower ball, a portion of mercury is expelled from it, so that the mer- 
cury may afterwards stand at a proper height in the tube when the instrument 
is cold. The tube is then melted with care by the blow-pipe flame below the 
ball a, and closed, or hermetically sealed, as in c. The thermometer is in this 
way properly filled with mercury, and contains no air. 

We have now an instrument in which we can nicely measure and compare 
any change in the bulk of the included fluid metal. Having previously made 
sure of the equality of the bore, it is evident that if the mercury swells up and 
rises two, three, four, or five inches in the tube, it has expanded twice, thrice, 
four or five times more than if it had risen only one inch in the tube. By 
placing a graduated scale against the tube, we can, therefore, learn the quan- 
tity of expansion by simple inspection. 

In order to have a fixed point on the scale, from which to begin counting the 
expansion of mercury by heat, we plunge the bulb of the thermometer into 
melting ice, and put a mark on the stem at the point to which the mercury 
falls. However frequently we do so with the same instrument, we shall find 
that the mercury always falls to the same point. This is, therefore, a fixed 
starting point. We obtain another fixed point by plunging the thermometer 
into boiling water. With certain precautions, this point will be found equally 
fixed on every repetition of the experiment. The most important of these 
precautions is, that the barometer be observed to stand at 29.8 inches, when 
the boiling point is taken. It will afterwards be explained that the boiling 
point of water varies with the atmospheric pressure to which it is subject at the 
time. 

Thermometers, which are properly closed, and contain no air can be in- 
verted without injury, and the mercury falls into the tube, producing a sound 



THE THERMOMETER. .35 

as water does in the water-hammer. When the instrument contains air, the 
thread of mercury is apt to divide on inversion, or from other circumstances. 
When this accident occurs, it is best remedied by attaching a string to the 
upper end of the instrument, and whirling it round the head. The detached 
little column of mercury generally acquires in this way a centrifugal force, 
which enables it to pass the air, and rejoin the mercury in the bulb. 

When the glass of the bulb is thin, it is proper to seal the tube as described, 
and to retain it for a few weeks before marking upon it the fixed points. 
Thermometers, however carefully graduated at first, are found in a short time 
to stand above the mark in melting ice, unless this precaution be attended to. 
Old instruments often err by as much as half a degree, or even a degree and 
a half in this way. The effect is supposed to arise from the pressure of the 
atmosphere upon the bulb, which, when not truly spherical, seems to yield 
slightly, and in a gradual manner. The chance of this defect may be avoided 
by giving the bulb a certain thickness. Mr. Crichton's thermometers, of which 
the freezing point has not altered in forty years, were all made unusually thick 
in the glass. But thickness has the disadvantage of diminishing the sensibility 
of the instrument to the impression of heat. 

. We have in this way the expansion marked off on the tube, which takes place 
between the freezing and boiling points of water. On the thermometer which 
is used in this country, and called Fahrenheit's, this space is subdivided into 
180 equal parts, which are called degrees. This division appears empirical, and 
different reasons are given why it was originally adopted. Fahrenheit was 
an instrument-maker in Hamburg, and as he kept his process for graduating 
thermometers a secret, we can only form conjectures as to what were the prin- 
ciples that guided him. 

It is more convenient to divide the space between the freezing and boiling 
of water into 100 equal parts, which was done in the instrument of Celcius, 
a Swedish philosopher. This division was adopted at a later period in France, 
under the designation of the centigrade scale, and is now generally used over 
the continent. The freezing point of water is called 0, or zero, and the boil- 
ing point 100. But in our scale, the Point is arbitrarily called 32°, or the 32nd 
degree; and consequently the boiling point is 32 added. 180, or the 212th 
degree.* 

The scale can easily be prolonged to any extent, above or below these 
points, by marking off equal lengths of the tube for 180 degrees, either above 
or below the space first marked. The degrees of contraction below zero, or 
0°, are marked by the minus sign ( — ,) and called negative degrees, in order 
to distinguish them from degrees of the same name above zero, or positive 
degrees. Thus, 47° means the 47th degree above zero, — 47°, the 47th 
degree under zero. 

The only other scale in use is that of Reaumur, in the north of Germany. 
The expansion between the freezing and boiling of water is divided into 80 



* A simple rule may be given for converting centigrade degrees into degrees Fahrenheit. 
100 degrees Centigrade being equal to 180 degrees Fahrenheit, 10 degrees C. — 16 degrees 
F., or 5 degrees C. — 9 degrees F. ; multiply the Centigrade degrees by 9, and divide by 
5, and add 32. Thus to find the degree F. corresponding with 50° C. 

50 
9 



5)450 

90 
add 32 



Or the 50° C. corresponds with the 122° F. 



36 



THE THERMOMETER. 



parts in this thermometer, 
in the following diagram. 



The relation between the three scales is illustrated 



Fahrenheit's 
scale. 



Fig. 9. 

Centigrade 
scale. 



— 100 



Reaumur's 
scale. 





— 80 

— 60 



40 



20' 



— 



The zero of our scale is 32 
degrees below the freezing 
point of water, and the expan- 
sions of mercury are available 
in the thermometer from — 39° 
to 600°; but about the latter de- 
gree, mercury rises in the tube 
in the state of vapour, so as to 
derange the indications and at 
about 660° it boils, and can no 
longer be retained in the glass 
vessel; while at the former low 
point it freezes or becomes so- 
lid. For degrees of cold below 
the freezing point of mercury, 
we must be guided by the con- 
tractions of alcohol, or spirits of 
wine, a liquid which has not 
been frozen by any degree of 
cold we are capable of pro- 
ducing. There is no reason, 
however, for believing that we 
have ever descended more than 
130 or 140 degrees below our 
zero. 
The zero of these scales has, therefore, no relation to the real zero of heat* 
or point at which bodies have lost all heat. Of this point we know nothing, 
and there is no reason to suppose that we have ever approached it. The 
scale of temperature may be compared to a chain, extended both upwards and 
downwards beyond our sight. We fix upon a particular link, and count 
upwards and downwards from that link, and not from the beginning of the 
chain. 

The means of producing heat are much more at our command, but we have 
no measure of it, of easy application and admitted accuracy, above the boiling 
point of mercury. Recourse has been had to the expansion of solids at high 
temperatures, and various pyrometers, or " measures of fire," have been pro- 
posed. Professor Daniel's pyrometer is a valuable instrument of this kind, 
but it has not yet come into general use. Its indications result from the dif- 
ference in the expansion by heat of an iron or platinum bar, and a tube of well- 
baked black-lead ware, in which the bar is contained. The metallic bar a is 
shorter than the tube, and a short plug of earthenware b is placed in the mouth 
of the tube above the iron bar, and so secured by a strap of platinum foil and 
a little wedge, that it slides with difficulty in the tube. By the expansion of 
the metallic bar, the plug of earthenware is pushed onwards, and remains in 
its new position after the contraction of the metallic bar on cooling. The ex- 
pansion of the iron bar thus obtained, is measured by adapting to the instru- 
ment an index, c, which traverses a circular scale, before and after the earth- 
enware plug has been moved outwards by the expansion of the metallic bar. 
The degrees marked on the scale are in each instrument compared experimen- 
tally with those of the mercurial scale, and the ratio marked on the instrument, 
so that its degrees are convertible into those of Fahrenheit, (Philosophical 
Transactions, 1830-31.) An air thermometer, of which the bulb and tube 
were of metal, has also been employed to explore high temperatures. In the 



THE THERMOMETER. 
Fig. 10. 



37 




ft 



a 



old pyrometer of Wedgwood, the degree of heat was estimated by the perma- 
nent contraction which is produced upon a pellet of pipe-clay; but the indica- 
tions of this instrument are fallacious, and it has long gone out of use. 

The applicability of the mercurial thermometer, to measure degrees of heat, 
depends upon two important circumstances, which involve the whole theory 
of the instrument: 

1st. The hollow glass ball, with its fine tube of uniform bore, is a nice 
fluid measure. The ball and part of the stem being filled with a fluid, the 
slightest change in the bulk of the fluid, which may arise from the application 
of heat or of cold to it, is conspicuously exhibited by the rise or fall of the 
fluid column in the stem. No more delicate measure of the bulk, of an in- 
cluded fluid could be devised. 

2nd. It fortunately happens that the expansions of the fluid metal, mer- 
cury, which we can thus measure so accurately, are proportional to the 
quantities of heat which produce them. But the mode in whicii this is 
proved, requires a little attention. Suppose we had two reservoirs, one con- 
taining cold, and the other hot water. Plunge a thermometric bulb contain- 
ing mercury first into the cold water, and mark at what point in the stem the 
mercury stands. Then plunge it into the hot water, and mark also the point 
to which the mercury now rises in the stem. We can obviously make a heat 
which will be half way exactly between the hot and cold water, by taking the 
same quantity of the hot and cold water and mixing them together. Now, 
does this half heat produce a half expansion in mercury? On trial we find 
that it does. In the mixture of equal parts of the hot and cold water, the 
mercury stands exactly half way between the marks, supposing the experi- 
ment to be conducted with the proper precautions. This proves that the dilata- 
tions of mercury are proportional to the intensity of the heat which produces 
them. In the mercurial thermometer, therefore, quantities or degrees of ex- 
pansion may be taken to indicate quantities or degrees of heat; and that is the 
principle of the instrument. 

The same correspondence exists between the expansions of air and the 
quantities of heat which produce them. Indeed in the case of air, the corre- 
spondence is rigidly exact, while in the case of mercury it is only a close ap- 




38 THE THERMOMETER. 

proximation. Thus Dulong and Petit found that the boiling point of mer- 
cury was, 

as measured by mercury in a syphon . . . 680°. 
the air thermometer .... 662°. 
„ mercury in glass, (Mr. Crichton) . 660°. 

A short table exhibiting the increasing rate of the expansions of mercury 
has already been given, but glass expands in a ratio increasing still more 
rapidly than this metal; so that the greater expansion of the mercury in the 
thermometer at high temperatures, is fortunately corrected by the increasing 
capacity of the glass bulb. 

Fixed oils and spirits of wine do not deviate far from uniformity in their 
expansions, at least at low temperatures, and therefore are sometimes used as 
thermometric liquids. 

Thermometers have been devised which indicate the highest and lowest 

temperature which has oc- 
Fig. 11. curred between two ob- 

servations, or are self-re- 
gistering. Six's thermo- 
meter, which was invented 
by Dr. Rutherford is of this 
kind. This instrument 
consists, properly speak- 
ing, of two thermometers, 
one o, of spirit of wine, 
and the other b of mercury, 
which are placed in the position represented in the figure, their stems being 
in a horizontal direction. The thermometer b is intended to indicate the 
maximum temperature. It contains, in advance of the mercury, a short piece 
of iron wire, which the mercury carries forward with it in dilating, and which 
remains in its advanced position, marking the highest temperature that has 
occurred, when the mercury withdraws. The minimum temperature is indi- 
cated by the spirit of wine thermometer a, which contains, immersed in the 
spirit, a small cylinder of ivory, which by a slight inclination of the instru- 
ment falls to the surface of the liquid without being able to pass out of it. 
When the thermometer sinks, the ivory is carried back in the spirit; but when 
the temperature rises, the alcohol only advances, leaving the ivory where it 
was. Its extremity most distant from the bulb then indicates the lowest tem- 
perature to which the thermometer had been exposed. Before another obser- 
vation is made, the ivory must be brought again to the surface of the alcohol, 
by a slight percussion of the instrument. 

Our notions of the range of temperature acquire all their precision from the 
use of the thermometer. Cold, for instance, is allowed a substantial existence 
as well as heat, in popular language. What is cold ? it is the absence of heat, 
as darkness is the absence of light. The absence of heat, however, is never 
complete but only partial. Water, after it is frozen into ice, cold as it is in 
relation to our bodies, has not lost all its heat, for it is easy to cool a ther- 
mometer far below the temperature of ice, and have it in such a condition as 
that it shall acquire heat, and be expanded by contact with ice; thus proving 
that the ice contains heat. Spirits of wine have not been frozen at the lowest 
temperature that has hitherto been attained; but even then this liquid possesses 
heat, and there is no doubt that if a sufficiently large portion of its heat were 
withdrawn it would freeze like other bodies. The following are interesting 
circumstances in the range of temperature : 



SPECIFIC HEAT. 



39 



—148° 

—135 

—91 

—58 

—60 

—55 

—47 

—39 

—7 

+7 

4-20 

+ 32 

+ 50 

+ 52 

+ 98 

+ 150 

+ 173 

+ 212 

+ 442 

+ 612 

+ 662 

+ 980 

+ 1141 

+ 1869 

+ 1873 

+2786 



Fahr. Greatest artificial cold. Thilorier.* 

Solid compound of alcohol and carbonic acid melts. 

Greatest artificial cold measured by Walker. 

Temperature of planetary space. Fourier. 

Greatest natural cold observed by Ross. 

Greatest natural cold observed by Parry. 

Sulphuric ether congeals. 

Melting point of solid mercury. 

A mixture of equal parts of alcohol and water freezes. 

A mixture of one part of alcohol and three parts of water 

freezes. 
Strong wine freezes. 
Ice melts. 

Medium temperature of the surface of the globe. 
Mean temperature of England. 
Heat of the human blood. 
Wood-spirit boils. 
Alcohol boils. 
Water boils. 
Tin melts. 
Lead melts. 
Mercury boils. 
Red heat. Daniell. 
Heat of a common tire. Do. 
Brass melts. Do. 
Silver melts. Do. 
Cast iron melts. Do. 



SPECIFIC HEAT. 

Equal bulks of different substances, such as water and mercury, require the 
addition of different quantities of heat to produce the same change in their 
temperature. This appears evident from a variety of circumstances. If two 
similar glass bulbs, like thermometers, one containing mercury and the other 
water, be immersed at the same time in a hot water bath, it will be found that 
the mercury bulb is heated up to the temperature of the water bath in half the 
time that the water bulb requires; and if the two bulbs, after having both at- 
tained the temperature of the water bath, be removed from it and exposed to 
the air, the mercury bulb will cool twice as rapidly as the other. These ef- 
fects must arise from the mercury absorbing only half the quantity of heat 
which the water does in being heated up to the same decree in the water bath, 
and from having consequently only half the quantity of heat to lose in the 
subsequent cooling. Again, if we mix equal measures of water at 70° and 
130°, the temperature of the whole will be 100°; or the hot measure of water, 
in losing thirty degrees, elevates the temperature of the cold measure by an 
equal amount. But if we substitute for the hot water in this experiment an 
equal measure of mercury at 130°, on mixing it with the measure of water at 
70° the temperature of the whole will not be 100°, but more nearly 90°. 
Here the mercury is cooled from 130° to 90°, or loses forty degrees of heat ; 
which have been transferred to the water, but which raise the' temperature of 
the latter only twenty degrees, or from 70° to 90°. To heat the measure of 



* [ — 146 Mitchell, at which temperature alcohol of .789, "assumed the appearance of 
melted wax — and sulphuric ether is not in the slightest degree altered." R. B.] 



40 



SPECIFIC HEAT. 



water at 70° to 100°, we must mix with it two, or a little more than two, equal 
measures of mercury at 130°, although one measure of water at 130° would 
answer the purpose. If, therefore, two measures of mercury, by losing thirty 
degrees of temperature, heat up only one measure of water by thirty degrees, 
it follows that hot mercury possesses only half the heat of equally hot water; 
or that water requires double the quantity of heat that is required by mercury, 
to raise it a certain number of degrees. This is expressed by saying that 
water has twice the capacity for heat that mercury possesses. 

It is more convenient to express the capacities of different bodies for heat, 
with reference to equal weights than equal measures of the bodies. On ac- 
curate trial, it is found that a pound of water absorbs thirty times more heat 
than a pound of mercury, in being heated the same number of degrees: the 
capacity of water for heat is, therefore, thirty times greater than that of mer- 
cury. The capacities of these two bodies are in the relation of 1000 to 33; 
and it is convenient to express the capacities for heat of all bodies, in relation 
to that of water as 1000. Such numbers are the specific heat of bodies. 

The best method of determining the capacity for heat, consists in allowing 
different substances to cool the same number of degrees in circumstances which 
are exactly similar; to enclose them, for instance, in a polished silver vessel, 
containing the bulb of a thermometer in its centre, and to place this vessel un- 
der a bell jar in which a vacuum is made. The time which the different sub- 
stances take to cool, enables us to calculate the quantity of heat which they 
give out. By this exact method, Messieurs Dulong and Petit determined the 
capacity for heat of the following substances; 

Specific heat.. 
. 1000 

188 



Water 

Sulphur 

Glass 

Iron 

Copper 

Zinc 

Silver 

Mercury 

Platinum 

Lead 



117 
110 
95 
93 
56 
33 
31 
29 



The method of cooling gives results so exact, as to allow the detection of an 
increase of capacity with the temperature. The capacity of iron, when tried 
between 32° and 212°, as was the case with all the bodies in the table, was 
110; but 115 between 32° and 392, and 126 between 32° and 662°. It hence 
follows, that the capacity for heat, like dilatation, augments in proportion as 
the temperature is elevated. Dulong and Petit likewise established a relation 
between the capacity for heat of metallic bodies and the proportion by weight 
in which they combine with oxygen; or any other substance, which will again 
be adverted to. 

Of all liquid or solid bodies, water has much the greatest capacity for heat. 
Hence the sea, which covers so large a proportion of the globe, is a great 
magazine of heat, and has a beneficial influence in equalizing atmospheric 
temperature. Mercury has a small specific heat, so that it is quickly heated 
or cooled, another property which recommends it as a liquid for the thermom- 
eter, imparting, as it does, great sensibility to the instrument. 

The determination of the specific heat of gases is a problem involved in the 
greatest practical difficulties; so that notwithstanding its having occupied the 
attention of some of the ablest chemists, our knowledge on the subject is still 





specific heat. 




same weight. 


Nitrogen 


275 


Nitrous oxide 


237 


Olefiant gas 


421 


Carbonic oxide 


2S8 


Steam 


847 



CONDUCTION OF HEAT. 41 

of the most uncertain nature. It has been concluded by Delarive and Marcet,* 
and by Mr. Haycraft,t that the specific heat of all gases is the same for equal 
volumes. But this opinion has been controverted by Dulong,i and by Dr. 
Ajohn;§ and most chemists are now disposed to place more reliance upon the 
old experiments of Delaroche and Berard than upon any others which have 
been subsequently published.^ Their method was to transmit known quan- 
tities of the gases, heated to 212° in a uniform current, through a serpentine 
tube, surrounded by water, the temperature of which was observed, by a deli- 
cate thermometer at the beginning and end of the process. Their results are 
as follows: 

Specific heat of gases referred to water, 

specific heat. 

same weight. 
Water 1000 

Air 267 

Hydrogen 3294 

Carbonic acid 22 L 

Oxygen 230 

It will be observed, that the capacity for heat of steam is less than that of 
an equal weight of water. Hence, the specific heat of a body may change 
with its physical state. Delaroche and Berard likewise observed that the 
capacity of a gas is increased by its rarefaction. When the volume of a gas 
is doubled, by withdrawing half the pressure upon it, its specific heat is not 
quite so much as doubled. This is the reason why a gas becomes cold in 
expanding. In the expanded state it requires more heat to sustain it at its 
former temperature, from the augmentation which has occurred in its capacity. 
Air expanded into double its volume is cooled 40 or 45 degrees; and it has its 
temperature raised to that extent by compression into half its volume; sud- 
denly condensed to one fifth of its volume by a piston in a small brass cylin- 
der, so much heat is evolved as to cause the ignition of a readily inflammable 
substance, such as tinder. 

COMMUNICATION OF HEAT BY CONDUCTION AND RADIATION. 

1. Conduction. When one extremity of a bar of iron is plunged into a fire, 
the heat passes through the bar in a gradual manner, being communicated from 
particle to particle, and after passing through the whole length of the bar, may 
arrive at the other extremity. Heat, when conveyed in this way, is said to 
be conducted. 

In the case of solid substances, the phenomenon of the conduction of heat 
is so simple and familiar, that little need be said on the subject. Different 
solid substances vary exceedingly from each other in their power to conduct 
heat. Dense or heavy substances are generally good conductors, while light 
and porous bodies conduct heat imperfectly. Hence the universal use of sub- 
stances of the latter class for the purposes of clothing. Count Rumford ob- 
served that the finer the fabric of woollen cloth is, the more imperfectly does 
it conduct. The down of the eider-duck appears to be unrivalled in this re- 
spect. Bad conductors are also the most suitable for keeping bodies cool, 
protecting them from the access of heat. Hence, to preserve ice in summer, 

* Annales de Ch. et. de Ph. t. 35, p. 5, and t. 41, p. 78. 
t Edinburgh Phil. Trans. 1824. 
t Annales de Ch. et. de Ph. t. 41, p. 113. 
§ Transactions of the Royal Irish Academy, 1837. 
^ Annales dc Chimie, t. 75; or Annals of Philosophy, vol. ii. 
4* 



42 



CONDUCTION OF HEAT. 



\va wrap it in flannel. Among good conductors of heat, the metals are the 
best. The relative conducting power of several bodies is expressed by the 
numbers in the following table, from the experiments of Despretz. 



Gold 


1000 


Tin 


303.9 


Silver 


973 


Lead 


179.6 


Copper 


898 


Marble 


23.6 


Platinum 


381 


Porcelain 


14.2 


Iron 


374.3 


Clay 


11.4 


Zinc 


363 . 







Glass is an imperfect conductor, for we can fuse the point of a glass rod in 
a lamp, holding it within an inch of the extremity. On the contrary, we find 
it difficult to heat any part of a thick metallic wire to redness in a lamp, owing 
to the rapidity with which the heat is carried away by the contiguous parts. 

Certain vibrations were observed by Mr. Trevelyan to take place between 
metallic masses having different temperatures, occasioning particular sounds, 
Fig 12 which appear to be connected with the conducting power 

of the metals.* Thus if a heated curved bar of brass b, 
be laid upon a cold support of lead /, of which the surface 
is flat, as represented in the figure, the brass bar, while 
communicating its heat to the lead, is thrown into a state 
of vibration, accompanied with a rocking motion and the 
production of a musical note, like that of. the glass har- 
monicon. The motion of the brass bar appears to de- 
pend upon a certain repulsion existing between heated 
surfaces, enhanced in this case by the low conducting power of the Tead, 
which allows its surface to be strongly heated by the brass. Professor Forbes 
finds that the most intense vibrations are produced between the best con- 
ductors and the worst conductors of heat, the latter being the cold bodies.! 

Our ordinary conceptions of the actual temperature of different bodies, are 
much affected by the conducting powers of these bodies. If we apply the 




Fig. 13. 




hand, at the same time, to a good and to a bad con- 
ductor, such as a metal and a piece of wood, which 
are exactly of the same temperature by the thermo- 
meter, the good conductor will feel colder or hotter 
than the other, from the greater rapidity with which 
it conducts away heat from, or communicates heat to 
our body, according as the temperature of the metal 
or wood happens to be above or below that of the 
hand applied to them. 

The diffusion of heat through liquids and gases is 
effected in a great measure, by the motion of their 
particles among each other. When heat is applied 
to the lower part of a mass of liquid, the heated por- 
tions become lighter than the rest, and ascend rapid- 
ly, conveying or carrying the heat through the mass 
of the fluid. In a glass flask, for instance, contain- 
ing water, with which a small quantity of any light 
insoluble powder has been mixed, a circulation of 
the fluid may be observed upon the application of 
the flame of a lamp to the bottom of the vessel, the 
heated liquid rising in the centre of the vessel, and 
afterwards descending near its sides, as represented 

* Phil. Mag. 3d series, vol. iii., 321. 
t Edin. Phil. Trans, vol. xii. 



RADIATION OF HEAT. 



43 



Fig. 14. 





in the annexed figure. But when heat is applied to the surface of a liquid, 
this circulation does not occur, and the heat is propagated very imperfectly 
downwards. It has even been doubted whether liquids conduct heat downwards 
at all, or indeed in any other way than by conveying it, as above described. 
It can be proved, however, that heat passes downwards in fluid mercury, and 
hence it is probable that all liquids possess a slight conducting power similar 
to that of solids. 

Let the endless tube represented in the accom- 
panying figure be supposed to be entirely filled 
with water, and the heat of a fire be applied to the 
lower portion of it at «, which is twisted into a 
spiral form, the water will immediately be set in 
motion, and made to circulate through the tube, 
from the expansion and ascent of the portion in cr, 
and the whole of the water in the tube will be 
brought in succession to the source of heat. The 
tube may be led into an apartment above d, and 
being twisted into another spiral at b a quan- 
tity of the heat of the circulating water will be 
discharged in proportion to the extent of surface 
of tube exposed. Water of a temperature con- 
siderably above 212° is made to circulate in 
this manner through a very strong drawn iron 
tube of about one inch in diameter, for the 
purpose of heating houses and public buildings. 
A slight waste of the water is found to occur, so 
that it is necessary to introduce a small quantity 
every few weeks by an opening and stop-cock c, in the upper part of the tube. 
Tubes of larger caliber, with water circulating below the boiling point, are 
likewise much used for warming large buildings. 

Air and gases are very imperfect conductors. Heat appears to be propa- 
gated through them almost entirely by conveyance, the heated portions of air 
becoming lighter, and diffusing the heat through the mass in their ascent, as in 
the case of liquids. Hence, in heating an apartment by hot air, the hot air 
should always be introduced at the floor or lowest part. The advantage of 
double windows for warmth depends in a great measure, on the sheet of air 
confined between them, through which heat is very slowly transmitted. In 
the fur of animals and in clothing, a quantity of air is detained among the 
loose fibres, which materially enhances their non-conducting property. In 
dry air, the human body can resist a temperature of 250° without inconve- 
nience, provided it is not brought into contact with good conductors at the 
same time. 

Radiation of Heat. Heat is also emitted from the surface of bodies in the 
form of rays, which pass through a vacuum, air, and certain other transparent 
media, with the velocity of light. It is not necessary that a body he heated to 
a visible redness to enable it to discharge heat in this manner. Rays of heat, 
unaccompanied by light, continue to issue from a hot body through the whole- 
process of its cooling, till it sinks to the actual temperature of the air or sur- 
rounding medium. The circumstance that bodies suspended in a perfect 
vacuum cool rapidly and completely, without the intervention of conduction, 
places the fact of the dissipation of heat by radiation, at low temperatures, 
beyond a doubt. 

The most valuable observations which we possess on this subject, were 
published by Sir John Leslie in his Essay on Heat, in 1804. Leslie proved 
that the rate of cooling of a hot body is more influenced by the state of its sur- 
face than by the nature of its substance. He filled a bright tin globe with hot 



44 



RADIATION OF HEAT, 



water, and observed its rate of cooling in a room of which the air was undis- 
turbed. A thermometer placed in the water cooled half way to the tempera- 
ture of the apartment in 156 minutes. The experiment was repeated, after 
covering the globe with a thin coating of lamp-black. The whole now cooled 
to the same extent as in the first experiment in 81 minutes; the rapidity of 
cooling being nearly doubled, merely by this change of surface. 

An experiment of Count Rumford is even more singular, Water, of the 
same temperature, was allowed to cool in two similar brass cylinders, one of 
which was covered by a tight investiture of linen, and the other left naked. 
The covered vessel cooled 10° in 36^ minutes, while the naked vessel required 
55 minutes; or the covering of linen, like the coating of lamp-black greatly ex- 
pedited the cooling, instead of retarding the escape of heat as might have been 
expected. The cooling was accelerated in the same manner, when the cylin- 
der was coated with black or white paint, or smoked by a candle. 

In determining the radiating power of different surfaces, Leslie generally 
made use of square tin canisters, of which the surfaces were variously coated, 
and which he filled with hot water. Instead of watching the rate of cooling, 
as in the experiments already mentioned, he presented the side of a canister, 
Fig. 15. having its surface in any 

particular condition, to 
a concave metallic mir- 
ror, which concentrated 
the heat falling upon it 
into a focus, where the 
bulb of an air-thermome- 
ter was placed to receive 
it, as represented in the 
annexed figure. The dif- 
ferential thermometer an- 
swered admirably for this 
purpose, as from its con- 
struction it is unaffected 
by the temperature of the room, while the slightest change in the temperature 
of the focal spot is immediately indicated by it. 

Two metallic mirrors were occasionally used in conducting these experi- 

ments. The mirrors being 
arranged so as to stand 
exactly opposite to each 
other, with their princi- 
pal axes in the same line; 
when a lighted lamp or 
hot canister is placed in 
the focus of one mirror, 
the incident rays are re- 
flected by that mirror 
against the other, and 
collected in its focus. 
The following table exhibits the relative radiating power of various sub- 
stances, with which the surface of the canister was coated, as indicated by the 
effect upon the differential thermometer: 





Lamp black 


100 


Tarnished lead . 


45 


Water by estimate . 


100-f 


Clean lead . 


19 


Writing-paper . 


98 


Iron, polished 


15 


Sealing-wax 


95 


Tin plate, gold, silver, 




Crown glass . 


90 


copper . 


12 


Plumbago 


75 







TRANSMISSION OF HEAT. 45 

It thus appears that lamp-black radiates five times more of the heat of boil- 
ing water than clean lead, and eight times more than bright tin. The metals 
have the lowest radiating power, which arises from their brightness and 
smoothness. If allowed to tarnish, their radiating power is greatly increased. 
Thus the radiating power of lead with its surface tarnished is 45, and with its 
surface bright, only 19; but glass and porcelain radiate most powerfully al- 
though their surface is smooth. When the actual radiating surface is metallic 
it is not affected in a sensible manner by the substance under it. Thus, glass 
covered with gold leaf possesses the radiating power of a bright metal. 

It appears, from the recent experiments of Prof. A. D. Bache, that the ra- 
diating power of any surface is not affected by its colour, at least in an appre- 
ciable degree. Hence, no particular colour of clothes can be recommended for 
superior warmth in winter. But the absorbent power of bodies for the heat of 
the sun depends entirely upon their colour.* 

The faculty which different surfaces possess of absorbing or of reflecting 
heat radiated against them, is connected with their own radiating power. 
Those surfaces which radiate heat freely, such as lamp-black, glass, &c, also 
absorb a large proportion of the heat falling upon them, and reflect little of it; 
while surfaces which have a feeble radiating and absorbing faculty, such as 
the bright metals, reflect a large proportion, as they absorb little, and form the 
most powerful reflectors. So that the good absorbents are found at the top, 
and the good reflectors at the bottom of the preceding table. The efficiency 
of a reflector depending upon its low absorbing power, reflectors of glass are 
totally useless in conducting experiments upon radiant heat. Metallic reflec- 
tors remain cold, although they collect much heat in their foci. 

These laws of the radiation of heat admit of some practical applications. If 
we wish to retard, as much as possible, the cooling of a hot fluid or other sub- 
stance, in what sort of vessel should we enclose it? In a metallic vessel, of 
which the surface is not dull and sooty, but clean and highly polished; for it 
has been observed that hot water cools twice as fast in a tin globe of which 
the surface is covered with a thin coating of lamp-black, as in the same globe 
when the surface is bright and clean. Hence, the advantage of bright metallic 
covers at table, and the superiority of metallic tea-pots over those of porcelain 
and stoneware. 

TRANSMISSION OF HEAT THROUGH MEDIA, AND THE EFFECT OF 

SCREENS. 

It has been shown by Dulong and Petit that hot bodies radiate equally in 
all gases, or exactly as they radiate in a vacuum. Hot bodies certainly cool 
more rapidly in some gases than in others, but this is owing to the mobility 
and conducting powers of the gases being different. 

Light of every colour, and from every source, is equally transmitted by all 
transparent bodies in the liquid or solid form, but this is not the case with heat. 
The heat of the sun passes through any transparent body without loss, but of 
heat from terrestrial sources, a certain variable proportion only is allowed to 
pass, which increases as the temperature of the radiant body is elevated. Thus, 
it was observed by Delaroche that, from a body heated to 182°, only l-40th 
of all the heat emitted passed through a glass screen: from a body at 346°, 
1-1 6th of the whole; and from a body at 960°, so large a proportion as l-4th 
appeared to pass through the screen. M. Melloni has, within the last few 
years, greatly extended our knowledge respecting the transmission of heat 
through media, in a series of the most profound researches.t In his experi- 

* Journal of the Franklin Institute, May and November, 1835. 

t The complete series of Melloni's Memoirs given in Mr. R. Taylor's Scientific Me- 
moirs, Nos. 1 and 3. 



46 



TRANSMISSION OF HEAT. 



ments, he made use of the thermo-electric pile to detect changes of temperature, 
an instrument which in his hands exhibited a sensibility to the impressions 
of heat vastly greater than that of the most delicate mercurial, or air thermom- 
eter. 

His instrument, or the thermo-multiplier, (see the annexed figure) consists 
of an arrangement of thirty pairs of bismuth and antimony bars contained in a 

Fig. 17. 




brass cylinder, t, and having the wires from its poles connected with an ex- 
tremely delicate magnetic galvanometer, n. The extremities of the bars at b 
being exposed to any source of radiant heat, such as the copper cylinder d, 
heated by the lamp /, while the temperature of the other extremities of the bars at 
c is not changed, a current of electricity passes through the wires from the 
poles of the pile, and causes the magnetic needle of the galvanometer to de- 
flect. The quantity of electricity circulating increases in proportion to the 
difference of the temperatures of the two ends b and c, that is in proportion 
to the quantity of heat falling upon b; and the effect of this current of electri- 
city upon the needle, or the deviation produced, is proportional to the quantity 
of electricity circulating, and consequently to the heat itself, — at least Melloni 
finds this correspondence to be exact through the whole arc, from zero to 20°, 
when the needle is truly astatic. 

Melloni proved that heat, which has passed through one plate of glass, be- 
comes less subject to absorption in passing through a second. Thus, of 1000 
rays of heat from an oil flame, 451 rays being intercepted in passing through 
four plates of glass of equal thickness — 

381 rays were intercepted by the first plate. 

43 ,, ,, by the second. 

18 ,, ,, by the third. 

9 ,, ,, by the fourth. 



451 



The rays appear to lose considerably when they enter the first layers of a 
transparent medium; but that portion of heat, which has forced its passage 
through the first layers, may penetrate, to a great depth. Transparent liquids 
are found to be less penetrable to radiant heat than solids. 

The capacity which bodies possess of transmitting heat does not depend 
upon their transparency; or bodies are not at all transparent to heat in the 
same proportion that they are transparent to light. Thus, plates of the fol- 
lowing transparent minerals, having a common thickness of 0.1031 of an inch, 
allowed very different proportions of the heat from the flame of an Argand 
oil-lamp to pass through them. 



TRANSMISSION OF HEAT. 47 



92 rays. 

62 „ 

62 „ 

62 „ 

57 „ 

52 „ 

33 „ 

29 „ 

20 „ 

15 „ 

15 „ 

12 „ 

'12 „ 

„ 



Of 100 incident rays, there were transmitted: 
By Rock-salt 
,, Mirror glass 
,, Rock-crystal 
,, Iceland spar 
• „ Rock-crystal, smoky and brown 
„ Carbonate of lead . 
,, Sulphate of barytes 
-,, Emerald 
,, Gypsum 
,, Fluor spar 
,, Citric acid 
„ Rochelle salt 
„ Alum .... 
,, Sulphate of copper 
A piece of smoky rock-crystal, so brown that the traces of letters on a 
printed page covered by it could not be seen, and which was fifty-eight times 
thicker than a transparent plate of alum, transmitted 19 rays, while the alum 
transmitted only 6. One substance which is perfectly opaque, a kind of glass 
used for the polarization of light, was found by Melloni to allow a considerable 
quantity of rays of heat to pass through it. He applies the term diather- 
manous to bodies which transmit heat, as diaphanous is applied to bodies 
which transmit light. Of all diaphanous or transparent bodies, water is in 
the least degree diathermanous. With the exception of the opaque glass re- 
ferred to above, all diathermanous bodies belong also to the class of diapha- 
nous bodies; for those kinds of metal, wood and marble which totally obstruct 
the passage of light, obstruct that of heat also. 

The proportion of heat, from various sources which radiates through a plate 
of glass, l-50th of an inch in thickness, was observed by Melloni to be as 
follows: 

Of 100 rays from the flame 
of an oil-lamp there were . . . .54 transmitted, 46 absorbed. 
,, ,, red hot platinum . 57 » 63 ,, 

„ ,, blackened copper, 

heated to 732° F. ... 12 „ 88 

,, ,, blackened copper 

heated to 212° .... 100 „ 

But the power of transmission, in the case of rock-salt, is the same for heat 
from all these sources, or for heat of all intensities; 92 percent, of the incident 
heat being transmitted by that body, whether it be the heat radiated from the 
hand or from a bright Argand lamp. Rock-salt stands alone in this respect 
among diathermanous bodies. This substance may be cut into lenses or 
prisms, and be used in concentrating heat of the very lowest intensity, or in 
decomposing it by double refraction, in the same manner as glass is employed 
in the case of the light of the sun. Indeed, rock-salt has become quite inva- 
luable in researches upon the transmission of heat. 

It thus appears that a body at different temperatures emits different species 
of rays of heat, which may be sifted or separated from each other by passing 
them through certain transparent media. They are all emitted simultaneously, 
and in different proportions by flame; but in heat from sources of lower inten- 
sity, some of them are always absent. The calorific rays of the sun are chiefly 
of the kind which passes through glass; but Melloni shows that the other spe- 
cies are not altogether wanting. The rays of heat emitted by the sun and other 



48 EQUILIBRIUM OF TEMPERATURE. 

luminous bodies are quite different rays from the rays of light with which they 
are accompanied. 

Of the Equilibrium of Temperature. When several bodies of various 
temperatures, some cold, and some hot, are placed near each other, their tem- 
peratures gradually approximate, and, after a certain period has elapsed, they 
are found all to be of one and the same temperature. To account for the produc- 
tion and continuation of this equilibrium of temperature, it is necessary to assu me, 
that all bodies are at all times radiating heat in great abundance in all directions, 
although their temperature does not exceed or even falls below the tempera- 
ture of the atmosphere. Hence, there is an incessant interchange of heat 
between neighbouring bodies; and a general equalization of temperature is 
produced, when every object receives as much radiated heat as it emits. 

This theory, which was first proposed by Prevost of Geneva, enables us to 
account for the apparent radiation of cold. Cold, we know, is a negative 
quality, being merely the absence of heat, and cannot therefore be radiated. 
Yet, when we place a lump of ice in the focus of a reflecting mirror, a ther- 
mometer in the focus of the opposite conjugate mirror is chilled. To account 
for this phenomenon we must remember that the temperature of the thermo- 
meter is stationary, only so long as it receives as much heat as it radiates. It 
is in that state before the experiment is made with the ice; for the air or any 
object which may happen to be in the other focus is of the same temperature 
as the ball of the thermometer. But it is evident that the moment ice is intro- 
duced into one focus, less heat will be sent from that to the other focus, than 
was previously transmitted, and than is necessary to sustain the thermometer 
at a constant temperature. The thermometer ball, therefore, giving out as much 
heat as formerly and receiving less in return, must fall in temperature. This is 
an experiment in which the thermometer ball is, in fact, the hot body. 

The doctrine of the radiation of heat was very happily applied to account 
for the deposition of Dew. A considerable refrigeration of the surface of the 
ground below the temperature of the air resting upon it, amounting to 10 or 20 
degrees, occurs every calm and clear night, and is caused by the radiation of 
heat from the earth (which is a good radiator) into empty space. Now, on 
becoming colder than the air above it, the ground will condense the moisture 
of the air in contact with it, and be covered with dew. For the air, however 
clear, is never destitute of watery vapour, and the quantity of vapour which 
air can retain depends upon its temperature, air at 32°, for instance, being ca- 
pable of retaining 1-1 50th of its volume of vapour while at 52° it can retain 
so much as l-86th of its volume. The greatest difference between the tempe- 
rature of the day and night in this country takes place in spring and autumn, 
and these are the seasons in which the most abundant dews are deposited. 

That the deposition of dew depends entirely upon radiation is fully esta- 
blished by the following circumstances; 1°. It is on clear and calm nights 
only that dew is observed to fall. When the sky is overcast with clouds, no 
dew falls; for then the heat which radiates from the earth, is returned by the 
clouds above, and prevented from escaping into space; so that the ground 
never becomes colder than the air. 2°. The slightest screen, such as a thin 
cambric handkerchief, stretched between pins, at the height of several inches 
above the ground, is sufficient to protect the objects below it from this chilling 
effect of radiation, and to prevent the formation of dew, or of hoar-frost upon 
them. This fact was well known to gardeners, and they had long availed 
themselves of it in protecting their tender plants from frost, before the laws of 
the radiation of heat came to be explained. 3°. Dr. Wells proved by nu- 
merous experiments that the quantity of dew which condenses on different 
objects exposed in the same circumstances, is proportioned to the radiating 
power of those substances. Thus when a polished plate of metal and a 



EQUILIBRIUM OF TEMPERATURE. 49 

quantity of wool are exposed together in favourable circumstances, scarcely a 
trace of dew is to be observed on the metal, while a large quantity condenses 
in the wool, the latter substance being incomparably the best radiator, and 
therefore failing to a much lower temperature than the metal. 

The same theory has been applied to explain a process for making ice 
followed by the native Indians near Calcutta. In that climate the temperature 
of the air rarely falls below 40° in the coldest nights; but the sky is clear and 
a powerful radiation takes place from the surface of the ground. Hence, 
water contained in shallow pans imbedded in straw, is often sheeted over with 
ice by a night's exposure. The water is certainly cooled by radiation from 
its surface, and not by evaporation; for the process succeeds best when the 
pans are placed in shallow trenches dug in the ground, an arrangement which 
retards evaporation; and no ice forms in windy weather, when evaporation is 
greatest. 

The morning frosts of autumn are first felt in sequestered situations, as in 
ravines closed on all sides, or along the low courses of rivers, where the 
cooling of the earth's surface by radiation is in the least degree checked by the 
movement of the air over it. These are also the very situations upon which 
the sun's rays produce the greatest effect in summer. 

Reverting again to the subject of the conduction of heat through solid bodies, 
it may now be stated, that there is every reason to believe that heat is propa- 
gated, even in that case, in a manner not unlike radiation. Heat, in its pas- 
sage through a bar of iron, is probably radiated from particle to particle; for 
the material atoms, of which the bar consist, are not supposed to be in abso- 
lute contact, although held near each other by a strong attraction. Radiation, 
as observed in air or a vacuum, may thus pass into conduction in the case of 
solids, without any breach of continuity in the natural law to which heat in 
motion is subject. Baron Fourier proceeds upon such an hypothesis in his 
mathematical investigation of the law of cooling by conduction in solid bodies, 
and obtains expressions which agree with his experimental results. 

We are now in a condition to advert with advantage to the equilibrium of 
the temperature of the earth. There can be no doubt of the existence, in this 
globe of ours, of a central heat. At a depth under the surface of the earth, 
not in general exceeding fifteen yards, the thermometer is perfectly stationary, 
not being affected by the change of the seasons; but at greater depths, the tem- 
perature progressively rises. M. Cordier, to whom we are indebted for a 
most profound investigation of this interesting subject, considers the two fol- 
lowing conclusions to be established by all the observations on temperature 
which have been made at considerable depths. 1st. That below the stratum 
where the annual variations of the solar heat cease to be sensible, a notable 
increase of temperature takes place as we descend into the interior of the earth. 
2ndly. That a certain irregularity must be admitted in the distribution of the 
subterraneous heat, which occasions the progressive increase of temperature to 
vary at different places. Fifteen yards has been provisionally assumed as the 
average depth which corresponds to an increase of one degree Fahrenheit. This 
is about 116 degrees for each mile. Admitting this rate of increase, we have 
at a depth of 30^ miles below the surface, a temperature of 3500°, which 
would melt cast iron, and which is amply sufficient to melt the lavas, basalts, 
and other rocks, which have actually been erupted from below in a fluid state. 
But this central heat has long ceased to affect the surface of the earth. Fou- 
rier demonstrates, from the laws of conduction, that although the crust of 
the globe were of cast iron, heat would require myriads of years to be trans- 
mitted to the surface, from a depth of 150 miles. But the crust of the globe 
is actually composed of materials greatly inferior to cast iron in conducting 
power. The temperature of the globe now depends upon the amount of heat 
5 



50 FLUIDITY. 

which it receives from the sun, compared with the heat radiated away from 
its surface into free space. There is reason to believe that no material change 
has occurred in the quantity of heat received from the sun during the histori- 
cal epoch. The radiation from the surface of the earth has its limit in 
the temperature of the planetary space in which it moves, which Fourier 
deduces, from calculation to be — 58°, and which Schwanberg, from a calcu- 
lation on totally different principles, estimates at — 58°. 6, a very close coin- 
cidence. This low temperature appears to be attained in the long absence of 
the sun during a polar winter, as Captain Parry found the thermometer to fall 
as low as — 55° at Melville Island, and Ross more lately observed a tempera- 
ture so low as — 60°. 

FLUIDITY AS AN EFFECT OF HEAT. 

We have already adverted to one of the general effects of heat upon bodies, 
namely, its power of causing them to expand which demanded our earliest at- 
tention, as it involves the principle of the thermometer. But heat, besides 
effecting changes in the bulk, is capable of effecting changes in the state of 
bodies. Matter is presented to us in three very dissimilar states or forms, 
namely, in the solid, liquid, and gaseous forms. It is believed that no body 
is restricted to any one of these forms, but that the state of bodies depends en- 
tirely upon the temperature in which they are placed. In the lowest 
temperatures, they are all solid, in higher temperatures they are converted 
into liquids, and in the highest of all they become elastic gases. The 
particular temperatures at which bodies undergo these changes are exceed- 
ingly various, but they are always constant for the same body. The first 
effect then of heat on the state of bodies is the conversion of solids into liquids; 
or heat is the cause of fluidity. 

Some substances, in liquefying, pass through an intermediate condition, 
in which it is difficult to say whether they are liquids or solids. Thus 
tallow, wax, and several other bodies pass through every possible degree of 
softness before they attain complete fluidity. Such bodies, however, are in 
general mixtures of two or more substances, which crystallize imperfectly. 
But ice, and the great majority of bodies, pass immediately from the solid into 
the liquid state. The temperatures at which bodies undergo this change are 
exceedingly various: 

Olive oil melts at 36° 

Ice „ 32 

Milk „ 30 

Wines „ 20 

Oil of terpentine „ — 14 

Mercury „ — 39 

Liquid ammonia „ — 40 

Ether „ —47 

If the bodies are in the fluid form, they freeze upon being cooled below the 
temperatures set against them. 

It may be added, in reference to this table, first, that in certain circum- 
stances, liquids can be cooled down several degrees below their usual freezing 
point before they be^in to congeal. Thus we may succeed, by taking certain 
precautions, in cooling a small quantity of water, in a glass tube, so low as the 
temperature 8°, or even as 5°, without its freezing; that is 24 or 27 degrees 
under its proper freezing point 32°. The water must be cooled without the 
slightest agitation, and no sand or angular body be in contact with it; for the 
instant any solid body is dropped into water cooled below its freezing point, 



Lead 


melts at 


612° 


Bismuth 


5* 


497 


Tin 


H 


442 


Sulphur 


5* 


226 


Wax 


11 


142 


Spermaceti 


11 


112 


Phosphorus 


11 


108 


Tallow 


11 


92 


Oil of Anise 


11 


50 



FLUIDITY. 51 

or a tremor is communicated to it, congelation commences, and the tempera- 
ture of the liquid starts up to 32°. But, on the other hand, we cannot heat a 
solid the smallest fraction of a degree above its proper melting point, without 
occasioning liquefaction. Hence it is not the freezing of water, but the melt- 
ing of ice, which takes place with rigorous constancy at 32° Fahrenheit. 

All salts dissolved in water have the effect of lowering the freezing tempe- 
rature of that liquid. Common culinary salt appears to depress this point 
lower than any other saline body; and the effect appears to be very .closely 
proportional to the quantity of salt in solution. A solution of 1 part of salt in 
4 of water freezes at 4°, and sea water, which contains l-30th of its weight of 
salt, freezes at 28°. 

But the principal fact to be adverted to in liquefaction, is the disappearance 
of a large quantity of heat during the change. Heat pours into a body during 
its melting, without raising its temperature in the most minute degree. This 
heat, which enters the body and becomes insensible or latent, merely serves 
to melt the body. We are indebted to Dr. Black for this observation, which 
involves consequences of greater importance than any other announcement in 
the theory of heat. 

Before Dr. Black's views were made known, fluidity was universally con- 
sidered as produced by a very small addition to the quantity of heat which a 
body contains, when it is once heated up to its melting point; that a solid body, 
when it is changed into a fluid, receives no greater addition to the heat within 
it than is indicated and measured by the elevation of the mercury in the ther- 
mometer. But Dr. Black objected to this opinion, as inconsistent with many 
remarkable facts, when considered properly. If we attend, for instance, to 
the manner in which ice and snow melt, when exposed to the air of a warm 
room, we can perceive, that however cold they may be at first, they are soon 
heated up to their melting point, and begin at their surface to be changed into 
water. Now if a complete change of these bodies into water required only the 
farther addition of a very small quantity of heat, a mass of them, though of 
considerable size, ought all to be melted in a few minutes or seconds more, 
the heat continuing to be communicated from the air around. But masses of 
ice and snow are well known to melt with extreme slowness, especially if they 
,be of a large size, as are those collections of ice and wreaths of snow, that are 
formed in some places during winter. These, after they begin to melt, often 
require many weeks of warm weather, before they are totally dissolved into 
water. The slow manner in which ice melts in ice houses is also familiarly 
known to all. 

By examining what happens in these cases, it mav easily be perceived that 
a very great quantity of heat must enter the melting ice, to form the water into 
which it is changed, and that the length of time necessary for the collection of 
so much heat from surrounding bodies, is the reason of the slowness with 
which the ice is liquefied. When melting ice is suspended in warm air, the 
entrance of heat into it is made sensible by a steam of cold air descending con- 
stantly from the ice, which may be perceived by the hand. It is, therefore, 
evident that the melting ice receives heat very fast, but the only effect of this 
heat is to change it into water, which is not in the least sensibly warmer than 
the ice was before. A thermometer applied to the drops or small streams of 
water as they come immediately from the melting ice, will point to the same 
degree as when applied to the ice itself. A great quantity of the heat, there- 
fore, which enters into the melting ice, has no other effect than that of giving 
it fluidity. The heat appears to be absorbed or concealed within the water, 
and cannot be detected by the thermometer. 

When ice is melted by means of warm water, this absorption of heat is 
made exceedingly obvious. Thus on mixing a pound of water at 172° with 



52 FLUIDITY. 

a pound of snow at 32°, the snow is all melted, and the mixture is two 
pounds of water of the temperature of 32°. In being cooled down from 172° 
to 32°, the hot water loses 140 degrees of heat, which convert the snow 
into water, indeed, but produce no rise of temperature in the mixture above the 
32 degrees originally possessed by the snow. 

Dr. Black proved {hat the heat which disappears in this manner is not ex- 
tinguished or destroyed, but remains latent in the water so long as it is fluid, 
and is extricated again when it freezes. 

In water that has been cooled below its usual freezing point, when the con- 
gelation is once determined, quantities of icy spiculse are produced in propor- 
tion to the depression of temperature, whilst at the same instant the tempera- 
ture of ice and water start up to 32°. The heat which thus appears was pre^ 
viously latent in that portion of the water which is frozen. The same disen- 
gagement of latent heat may be conveniently illustrated by means of a super- 
saturated solution of sulphate of soda, formed by dissolving, at a high tempe- 
rature, three pounds of the salt in two pounds of water. When this liquid is 
allowed to cool undisturbed and with a few drops of oil on its surface, it re- 
mains fluid, although containing a much greater quantity of salt in solution 
than the water could dissolve at the temperature to which it has fallen. But 
the suspended congelation of the salt being determined by the introduction of 
any solid substance into the solution, the temperature then often rises 30 and 
even 40 degrees, while crystals of sulphate of soda shoot rapidly through the 
liquid. 

Wax, tallow, sulphur and all other solid bodies are melted in the same man- 
ner as water, by the assumption of a certain dose of heat. The latent heat 
which the following substances possess in the fluid form was, with the excep- 
tion of water, determined by Dr. Irvine. 

Latent heat. 

Water 140 degrees 

Sulphur 145 „ 

Lead ...... 162 „ 

Bees' wax . . . . . 175 „ 

Zinc . . . . . . 493 „ 

Tin 500 „ 

Bismuth ,. ..... 550 „ 

Even in the solid form certain bodies admit of a variation in their structure 
and properties from the assumption or loss of latent heat. Dr. Black made it 
appear probable that metals owe their malleability and ductility to a quantity of 
latent heat combined with them. When hammered they become hot from the 
disengagement of this heat, and at the same time become brittle. Their mal- 
leability is restored by heating them again in a furnace. Sugar, it is well 
known, may exist as a transparent and colourless body, with the physical pro- 
perties of glass, or as a white and opaque, because a granular or crystalline 
mass. The transition from the glassy to the granular state is attended by a 
very remarkable evolution of heat, which appears to have escaped the notice of 
scientific men. If melted sugar be allowed to cool to about 100°, and then, 
while it is still soft and viscid, be rapidly and frequently extended and doubled 
up, till at last it consists of threads, the temperature of the mass quickly rises 
so as to become insupportable to the hand. Applying the thermometer, I found 
the temperature of a considerable mass to rise from 105° to 175° in less than 
two minutes. After this liberation of heat, the sugar on again cooling is no 
longer a glass, but consists of minute grains, and has a pearly lustre. The same 
change may occur in a gradual manner, as when a clear stick of barley sugar 
becomes white and opaque in the atmosphere ; but then we have no means of 
observing the escape of the latent heat on which the change depends. It may 



FLUIDITY. 53 

be inferred that glass itself, like transparent barley-sugar, owes its peculiar con- 
stitution and properties to the permanent retention of a certain quantity of latent 
heat. Of this heat glass can be deprived, by keeping it long in a soft state ; it 
then becomes granular, and passing into the condition of Reaumur's porcelain 
loses all the characters of glass. 

It is not unlikely that the dimorphism of a body, or its property to assume 
two different crystalline forms, may likewise depend upon the retention of a 
certain quantity of latent heat by the body in the one form and not in the other. 
Thus sulphur assumes two forms, one on cooling from a state of fusion by heat, 
another in crystallizing at a lower temperature, and probably with the retention 
of less latent heat, from a solution of sulphuret of carbon; in charcoal and 
plumbago, again, we have carbon which has assumed the solid form at a high 
temperature, and possibly with the fixation of a quantity of latent heat which 
does not exist in the diamond; another form of the same body. 

When a solid body is melted by the intervention of some affinity, without 
heat being applied to it, cold is generally produced. Thus most salts occasion 
a reduction of temperature, in the act of dissolving in water, which requires 
them to become fluid. Nitre, for instance, cools the water in which it is dis- 
solved 15 or 18 degrees. A mixture of five parts of sal ammoniac and five of 
nitre, both finely powdered, dissolved in nineteen parts of water, may reduce its 
temperature from 50° to 10°, or considerably below the freezing point of pure 
water. These salts are necessitated, by their affinity for water, to dissolve when 
mixed with it and to become fluid, a change which implies the assumption of 
latent heat. Most of our artificial processes for producing cold are founded 
upon this disappearance of heat during liquefaction. A very convenient pro- 
cess for freezing a little water, without the use of ice, is to drench finely pow- 
dered sulphate* of soda with the undiluted hydrochloric acid of the shops. 
The salt dissolves to a greater extent in this acid than in water, and the tem- 
perature may sink from 50° to 0°. The vessel in which the mixture is made, 
becomes covered with hoar frost, and water in a tube immersed in the mixture 
is speedily frozen. " 

The same affinity between salts and water may be token advantage of to 
cause the liquefaction of ice, as when common salt is strewed upon pavements 
covered with ice, to melt it. On mixing snow with a third of its weight of 
salt, the snow is melted, and the temperature sinks nearly to 0°. It was in this 
way that Fahrenheit is supposed to have obtained the zero of his scale. Ices 
for the table are always made in summer by mixing roughly pounded ice and 
salt together, and immersing the cream, or other liquid to be frozen, contained 
in a thin metallic pan, in the cold brine which is produced by the melting of 
the ice. 

The liquefaction of snow by means of the salt, chloride of calcium, occa- 
sions a still greater degree of cold. To prepare this salt, marble or chalk is 
dissolved in hydrochloric acid, and the solution evaporated by a temperature 
not exceeding 300°. It should be stirred, as it becomes dry at this tempera- 
ture; and is obtained in a crystalline powder; being the combination of chloride of 
calcium with two atoms of water. .When three parts of this salt are mixed 
with two of dry snow, the temperature is reduced from 32° to— 50°. In at- 
tempting to freeze mercury by means of this mixture, it is advisable to make 
use of not less than three or four pounds of the materials. When the ma- 
terials are divided, and the mercury is first cooled considerably by one portion, 
it rarely fails in being frozen when transferred into another portion of the 
mixture. For producing still more intense degrees of cold, the evaporation 
of highly volatile liquids, of fluid carbonic acid, for instance, affords the most 
efficient means. 

5* 



54 



VAPORIZATION. 



VAPORIZATION. 



We have now to consider the second general effect of heat: vaporization, or 
the conversion of solids and liquids into vapour. Vapours, of which steam 
is the most familiar to us, are light, expansible, and generally invisible gases, 
resembling air completely in their mechanical properties, while they exist, but 
subject to be condensed into liquids or solids by cold. Water undergoes a 
great expansion when converted into steam, a cubic inch of water becoming, 
in ordinary circumstances, a cubic foot of steam; or more strictly, one cubic 
inch of water, when converted into steam, expands into 1694 cubic inches. 

This, change, like fluidity, is produced by the addition of heat to the body 
which undergoes it. But a much larger quantity of heat enters into vapours 
than into liquids, into steam than into water. If over a steady fire a certain 
quantity of ice-cold water requires one hour to bring it to the boiling point, it 
will require a continuance of the same heat for five hours more to boil it off 
entirely. Yet liquids do not become hotter after they begin to boil, however 
long, or with whatever violence, the boiling is continued: for if a thermometer 
be plunged into water, and the point marked where it stands at the beginning of 
the boiling, it will be found to rise no higher, although the boiling be continued 
for a long time. 

This fact is of importance in domestic economy, particularly in cookery; and 
attention to it would save much fuel. Soup, &c. made to boil in a gentle way, 
by the application of a moderate heat, are just as hot as when they are made 
to boil on a strong fire with the greatest violence; when water in a boiler is 
once brought to a boiling point, the fire may be reduced, as having no farther 
effect in raising its temperature, and a moderate heat being sufficient to pre- 
serve it. 

The steam from boiling water, when examined by the thermometer, is found 
to be no hotter than the water itself. What then becomes of all the heat which 
is communicated to the water, since it is neither indicated in the steam nor in the 
water? It enters into the water, and converts it into steam, without raising its 
temperature. As much heat disappears as is capable of raising the tempera- 
ture of the portion of water converted into steam 1000 degrees, or what is the 
same thing, as would raise the temperature of one thousand times as much 
water one degree. This is now generally assumed to be the amount of the 
latent heat of steam. Dr. Black found it to be about 960 degrees, Mr. Watt 
940 degrees, and Lavoisier rather more than 1000 degrees. 

Several circumstances may be remarked during the occurrence of this change 
in water. On heating water gradually in a vessel we first observe minute bub- 
bles to form in the liquid and rise through it, which consist of air. As the 
temperature increases, larger bubbles are formed at the bottom of the vessel, 
which rise a little way in the liquid, and then contract and disappear, producing a 
hissing or simmering sound. But, as the heating goes on, these bubbles, 
which are steam, rise higher and higher in the liquid, till at last they reach its 
surface and escape, producing a bubbling agitation, or the phenomenon of 
ebullition. The whole process of boiling is beautifully seen in a glass vessel. 
It will be remarked that steam itself is invisible; it only appears when con- 
densed again into minute drops of water by mixing with the. cold air. 

It was first observed by Guy-Lussac, that liquids are converted more easily 
into vapour when in contact with angular and uneven surfaces, than when the 
surfaces which they touch are smooth and polished. He also remarked that 
water boils at a temperature two degrees higher in glass than in metal; so that 
if into water, in a glass flask, which has ceased to boil, we drop a twisted piece 
of cold iron wire, the boiling is resumed: it is only in vessels of metal that the 



VAPORIZATION. 55 

boiling point is regular, and should be taken in graduating thermometers. It 
has lately been remarked by Mr. Scrymgeour, of Glasgow, that if oil be pre- 
sent with water, the boiling point of the water is raised a few degrees, in any 
kind of vessel. The reason why water, in these circumstances, does not pass 
into vapour at its usual boiling point, is not distinctly understood. The water 
appears to be in a precarious state of equilibrium, as in the other analogous 
case, when cooled with caution in a smooth glass vessel considerably under its 
usual freezing point. The introduction of an angular body into the water is 
sufficient, in either instance, to induce the suspended change. The same irregular 
deviation of the boiling point in glass vessels, takes place in other liquids as 
well as water, and in some of them to a much greater extent.* 

There is a curious circumstance in regard to boiling, which is a matter of 
common observation in some shape or other. When a little water, (a few 
drops) is thrown into a metallic cup, hotter than the boiling point of water, the 
hotter the cup is, the less rapidly does the water boil away. We should expect 
the reverse, or that the hotter the metallic cup, the more quickly would the 
water be dissipated. The cause of the phenomenon appears to be this. Water 
exhibits an attraction for the surface of almost all solids at low temperatures, 
and wets them. Fluid mercury exhibits the opposite property, or a repulsion 
for most surfaces. This attraction of water for surfaces brings it into the closest 
contact with them, and greatly promotes the communication of heat by a heated 
vessel to the water contained in it. But heat appears to develope a repulsion 
power in bodies, and it is probable that above a particular temperature the 
heated metal no longer possesses this attraction for water. The water, not 
being attracted to the surface of the hot metal, and induced to spread over it, is 
not rapidly heated, and therefore boils off slowly. A rude method of judging of 
the degree of heat is founded on the same principle, and is seen familiarly ex- 
emplified in the laundry. The heat of the smoothing iron is judged of by its 
effects by a drop of saliva let fall upon it. If the drop do not boil, but run along 
the surface of the metal, the iron is considered sufficiently hot; but if the drop 
adheres and is rapidly dissipated, the temperature is considered low. 

The temperature at which any liquid boils is not fixed (like the melting point 
of solids,) but depends entirely upon a particular circumstance, — the degree of 
pressure to which the liquid is at the time subject. Liquids are in general 
subject to the pressure of the atmosphere; for although the air is an exceedingly 
light substance, being 815 times. lighter than water, yet by reason of its great 
quantity and height, it comes to weigh with considerable force upon the earth. 
This is called the atmospheric pressure, and amounts to no less than fifteen 
pounds upon each Square inch of surface. The force with which air presses upon 
a man of ordinary size has been estimated at fifty tons; yet, from all the cavi- 
ties of the animal frame being filled with equally elastic air, we support this 
great pressure without being sensible of it; indeed, we should suffer the greatest 
inconvenience from its sudden removal. Now the pressure of the atmosphere 
is not always the same at the same place, but is found by the barometer to vary 
within the limits of one tenth of the whole pressure. This difference affects the 
boiling point to the extent of 4j degrees. Thus, when the height of the mer- 
cury in the barometer is expressed by the numbers in the first column, water 
boils at the temperatures placed against them in the second column. 

* [The temperature of boilingr water in glass vessels varies from 212°, 54, F. to 215°, 6, 
in metallic vessels from 212°, 27 to 212°, 36. It is only when the vessel, either glass or 
metal, is covered with a thin film of sulphur, shell-lac or some analogous substance, that 
boiling takes place at 212° as indicated by the temperature of the boiling liquid and of the 
vapour produced being exactly the same. Marcet. Annal. de Chim. et Phys. R. B.] 



56 VAPORIZATION. 

Barometer 



in inches 


of mercury 


water boils 


27.74 


• • • 


208° 


28.29 


. • • 


209 


28.84 


■ . . • 


210 


29.41 


... 


211 


29.8 


... 


212 


30.6 


. 


213 



It appears, from this table, that for every inch of variation in the barometer, 
the boiling point of water varies 1.76 degree. And consequently a rise or fall 
in the barometer of 0.1 inch, raises or lowers the boiling point 0.176 degree. 
On this account the pressure of the atmosphere must be attended to in fixing 
the boiling point of water on thermometers. Water boils at 212°, only when 
the pressure of the atmosphere is equivalent to a column of 29.8 inches mer- 
cury. 

The pressure of the atmosphere will be greatest at the level of the sea, and 
will diminish as we ascend to any height above it, for then we have less of the 
atmosphere above and pressing upon us, part of it being below us. Hence, 
water boils on the tops of mountains at a considerably lower temperature than 
at their bases. On the top of Mount Blanc, which is the pinnacle of Europe, 
water was observed by Saussure to boil at 184°. In deep pits, on the other 
hand, water requires a higher temperature to boil it, than at the surface of the 
earth. An instrument has been constructed for ascertaining the heights of 
mountains on this principle. It consists essentially of a thermometer, graduated 
with great care about the boiling point of water, by means of which the tempe- 
rature at which water boils at different altitudes can be ascertained with minute 
accuracy. A difference of one degree of temperature is occasioned by an ascent 
of 530 feet. 

When the pressure on liquids is removed by artificial means, they boil at 
greatly reduced temperatures. This may be done by placing them under the 
receiver of an air-pump, and exhausting. When the whole air is withdrawn, 
liquids in general boil about 145 degrees under the temperature which they re- 
quire to make them boil when subject to the atmospheric pressure. In a good 
vacuum water will boil at 67°. This fact is also illustrated by a simplejexperiment 
which any one may perform. A flask containing boiling water is closed with a 
cork, while the upper part is filled with steam. The boiling in the flask may 
be renewed by plunging it into cold water; and the colder the water the brisker 
will the ebullition become. But the boiling is instantly checked by removing 
the flask from the cold water and immersing it in very hot water. On corking 
the flask, the ebullition ceased from the pressure exerted by the confined steam 
upon the surface of the hot water ; but, on plunging the flask into cold water, 
this ste&m was condensed, and the water began to boil under the reduced pres- 
sure. On removing the flask to the hot water, the steam above ceased to be 
condensed, and by its pressure stopped the boiling. On the other hand, in a 
Papin's digester, which is a tight and strong kettle with a safety valve, water 
may be raised to 3 or 400° without ebullition; but the instant that this great 
pressure is removed, the boiling commences with prodigious violence. 

The facility with which liquids boil under reduced pressure is frequently taken 
advantage of in the arts, in "concentrating liquors which would be injured in 
flavour or colour by the heat necessary to boil them under the pressure of the 
atmosphere. The late Mr. Howard applied this principle in concentrating 
syrup of the sugar, which is apt to be browned when made to boil under the 
usual pressure. He thus boiled syrup at 150° applying heat to it in a pan 
covered by an air-tight lid, and pumping off the air and steam from the upper 
part of the pan by means of a steam-engine. This was the most essential part 



VAPORIZATION. 



57 



of his patent process, by which nearly the whole of the loaf sugar consumed in 
this country, has been manufactured for several years. 

In the same apparatus vegetable infusions may be inspissated, or reduced to the 
state of extracts, for medical purposes with great advantage. When an ex- 
tract is prepared in the ordinary way, by boiling down an infusion or expressed 
juice in an open vessel, under atmospheric pressure, a considerable and variable 
proportion of the active principle is always destroyed by the high temperature 
and exposure to the air. But the extract is not injured when the infusion of 
juice is evaporated at a low temperature, and without access of air, and is 
generally found to be a more active medicine. 

The temperatures at which different liquids are converted into vapour are 
exceedingly various ; but other things remaining the same, the boiling tempe- 
rature is constant for any particular liquid. The following table exhibits the 
boiling points of a few liquids, in which that point has been* determined with 
precision. 



843) 



Boilinsr poinU 

52 a 

96 

110 

140 

173 

192 

212 

248 

300 

314 

551 

620 

630 

662 



Hydrochloric ether 

Sulphuric ether 

Bisulphuret of carbon 

Ammonia, (sp. gr. 0.945) 

Alcohol, (sp. gr. 0.798) . 

Naphtha . . . . 

Water . 

Nitric Acid, (sp. gr. 1.42) 

Crystallized chloride of calcium 

Oil of turpentine . 

Phosphorus 

Sulphuric acid, (sp. gr. 1, 

Whale oil . 

Mercury 

The boiling point of water is uniformly elevated, by the solution of salts in 
the fluid : but much more so by some salts than others. Tables have been 
constructed of the boiling points of saline liquors, which are of useful application 
when we wish to maintain a steady temperature somewhat above 212°. Thus, 
water saturated with common salt, (100 water to 30 salt,) boils at 224° ; satu- 
rated with nitrate of potash, (100 water to 74 salt,) it boils at 238° ; saturated 
with chloride of calcium, at 264°. 

When steam from water is confined, it increases in temperature and acquires 
great force, and the experiment can only be performed with safety in a boiler 
possessed of a safety valve. This is a small lid in the upper part of the boiler, 
properly loaded, according to the force of the steam to be generated. The 
steam of boiling water occasions a severe scald, if allowed to condense upon the 
body. But when steam from water under pressure, or " high pressure" steam, 
which may be of a much higher temperature than boiling water, issues into the 
air, the hand may be directly exposed to it with impunity ; and a thermometer 
placed in it, shows that its temperature is greatly below that of boiling water. 
This singular property of high pressure steam is connected with the great ex- 
pansion which it undergoes on escaping into the air from the vessel in which it 
was confined ; elastic bodies having a tendency when compressed, to fly asunder, 
not only to their original dimensions, but beyond them. The steam is greatly 
expanded and at the same time mixed with air, which prevents it from after- 
wards collapsing. Now, after being incorporated with several times its bulk of 
air, steam is not easily condensed, but becomes low-pressure steam, and may 
have its condensing point reduced from above 212° to 120° or 130°. Hence 



58 



VAPORIZATION. 



the heat which it is capable of communicating, while condensing upon the hand 
held in it, is of much less intensity than that of ordinary steam, and inadequate 
to occasion scalding. 

Steam, when heated by itself, apart from the liquid which produced it, does 
not possess a greater elasticity than an equal bulk of air confined and heated to 
the same degree, and may be heated to redness without acquiring great elastic 
force. But if water be present, then more and more steam continues to rise, 
adding its elastic force to that of the vapour previously existing, so that the 
pressure becomes excessive. 

The elastic force of steam at temperatures above 212° is determined by heat- 
ing water in a stout globular vessel containing mercury rn, (see Figure) and 
water w, and having a long glass tube t, t, screwed into it, open at both ends, 
and dipping into the mercury, having a scale a, divided into inches applied to 
it. The globular, vessel has two other openings, into one of which a stopcock b 



Fig. 18. 



cc 



is screwed, and into the other a thermometer 
/, having its bulb within the globe. The water 
is boiled in this vessel for some time, with the 
stopcock open, so as to expel all the air. On 
shutting the stopcock, and continuing the heat, . 
the temperature of the interior, as indicated by 
the thermometer, now rises above 212°, at 
which it was stationary while the steam gene- 
rated was allowed to escape. The steam in the 
upper part of the globe becomes denser, more 
and more steam being produced, and forces the 
mercury to ascend in the gauge tube, 1 1 to a 
height proportional to the elastic force of the 
steam. The height of the mercurial column 
may be taken to express the elastic force or 
pressure of the steam produced at any particu- 
lar temperature above 212°. The weight of 
the atmosphere itself is equivalent to a column 
of mercury of 30 inches, and this pressure has 
been overcome by the steam at 212°, before it 
began to act upon the mercurial gauge. For 
every thirty inches that the mercury is forced 
up in the gauge tube by the steam, it is said to 
have the pressure or elastic force of another 
atmosphere. Thus, when the mercury in the 
tube stands at thirty inches, the steam is said 
to be of two atmospheres; at 45 inches, of two 
and a half atmospheres ; at 60 inches, of three 
atmospheres, and so on. 

Experiments have been made on the elastic 
force of steam by Professor Robinson, Mr. 
Southern, Mr. Watt, Dr. Ure, and others ; but 
all preceding results have been superseded by 
those of a commission of the French Academy, 
appointed by the French government to inves- 
tigate the subject, from its importance in connexion with the steam engine. 
Their results, which are expressed in the following table, were obtained by ex- 
periment, up to a pressure of 25 atmospheres. The higher pressures were calcu- 
lated by extending the progression observed at lower temperatures. 




VAPORIZATION. 



59 



Elasticity of steam 


Temp. Fahr. 


Elasticity of steam 


Temp. Fahr, 


taking atmospheric 




taking atmospheric 




pressure as unity. 




pressure as unity. 




1 


212.0 


13 


380.66 


.11 


233,96 


14 


386.94 


2 


250.52 


15 


392.86 


%l 


263.84 


16 


398.48 


3 


275. J 8 


17 


403.82 


H 


285.08 


18 ■ 


408.92 


4 


293.72 


19 


413.78 


4| 


300.28 


20 


418.46 


5 


307.5 


21 


422.96 


H 


314.24 


22 


427.28 


6 


320.36 


23 


431.42 


H 


326.26 


24 


435.56 


7 


331.70 


25 


439.34 


7 1 


336.86 


30 


457.16 


8 


341.78 


35 


472.73 


9 


350.78 


40 


486.59 


10 


358.88 


45 


491.14 


11 


366.85 


50 


510.60 


12 


374.00 







Some curious experiments were made by M. Cagnard de la Tour on the va- 
pour from various liquids at very high temperatures, and under great pressures. 
He filled a small glass tube in part with ether, alcohol, or water, and sealed it 
hermetically. The tube was then exposed to heat, till the liquid passed entire- 
ly into vapour. Ether became gaseous in a space scarcely double its volume 
at a temperature of 320°, and the vapour exerted a pressure of no more than 38 
atmospheres. Alcohol became gaseous in a space about thrice its volume at the 
temperature 404£°, with a pressure of about 139 atmospheres. Water acted 
chemically on the glass and broke it; but adding a little carbonate of soda to it, 
the water became gaseous in a space four times its volume at the temperature 
at which zinc melts, or about 648°. These results are singular, in so far as the 
pressure or elastic force of the vapours proves to be much smaller than that 
which corresponds with their calculated density. It thus appears that highly 
compressed vapours lose a portion of their elasticity, or yield more to a certain 
pressure than air, by calculation, would do. 

The latent heat of the vapours of several other bodies besides water has been 
determined, and found to have a relation to the volumes of the vapours. Thus, 
when equal weights of water and oil of turpentine are converted into vapour 
under the same pressure, the quantity of heat rendered latent by the turpentine 
vapour is not more than one-fifth of the latent heat assumed by the water vapour; 
but the bulk of the latter vapour is about five times greater than that of the for- 
mer. The table below exhibits the latent heat of equal weights of several va- 
pours, as ascertained by Dr. Ure. He distilled, in all cases, 200 grains of the 
liquid, from a small retort, and condensed the vapour in a thin glass globe, sur- 
rounded with a certain quantity of water at a known temperature, contained in 
a glass basin. To prevent the air from exercising an influence" on the tempe- 
rature of the water in the basin, care was taken that the water should be three 
or four degrees below the temperature of the air at the beginning of the expe- 
riment, while it was not afterwards heated more than the same number of de- 
crees above the atmospheric temperature by the condensation of the vapour. A 
thermometer of great delicacy was continually moved through the water, and 
its indications were read off to small fractions of a degree. The latent heat of 



60 



VAPORIZATION. 



457 

313 „ 
184 „ 
184 „ 

550 

866 „ 
903 
to their volume, as these 



each vapour was of course proportional to the rise of temperature which oc- 
curred in the condensing water. 

Equal weights. Latent heat. 

Vapour of water 1000 degrees. 

Alcohol (specific gravity 0.825) . 
Ether (boiling point 112) . 
Petroleum . . 

Oil of turpentine 

Nitric acid (specific gravity 1.494) 
Liquid ammonia (specific gravity 0.978) 
Vinegar (specific gravity 1.007) 
If the latent heat of different vapours be proportional 
numbers seem to indicate, the same bulk of vapour will be produced from all 
liquids with the same expenditure of heat, and hence there can be no advantage 
in substituting any other liquid for water, as a source of vapour, in the steam 
engine. 

The latent heat of the vapour of water itself increases with its rarity at low 
temperatures, and diminishes with its increasing density at high temperatures. 
Water may easily be made to boil in a vacuum at the temperature of 100°, but 
the steam produced is much more expanded and rare than that produced at 212°, 
and has a greater latent heat. Hence there is no fuel saved by distilling in vacuo. 
It has been shown, by Mr. Sharpe of Manchester, that whatever be the tempe- 
rature of steam, from 212° upwards, if the same weight of it be condensed by 
water, the temperature of the water will always be raised the same number of 
degrees ; or the latent and sensible heat of steam added together, amount to a 
constant quantity. We may hence deduce a simple rule for ascertaining the 
latent heat of steam at any particular temperature. The sensible heat of steam 
at 212° maybe assumed as 212 degrees neglecting the heat which it has below 
zero Fahrenheit, and the latent heat of such steam is 1 000 degrees, of which the 
sum is 1212 degrees. To calculate the latent heat of steam at any particular 
temperature above 212°, subtract the sensible heat from this constant number 
1212. Thus the latent heat of steam at 300° is 1212—300, or 912 degrees. 
The same relation between the latent and sensible heat of vapour appears to 
exist at temperatures below 212°, and we may, therefore, calculate the latent 
heat of vapour, below that temperature, by the same rule. 

Temperature. Latent heat of equal weights of steam. 

0° 1212 degrees 

32 . . . . 1180 „ 

100 ..... 1112 „ 

150 • . . . 1062 „ 

212 . . . . 1000 „ 

250 . . . . 962 „ 

The latent heat of other vapours, such as that of alcohol, ether, and oil of 
turpentine, has been found by Despretz to vary according to the same law. 

From the large quantity of heat which steam possesses, and the facility with 
which it imparts it to bodies colder than itself, it is much used as a vehicle for 
the communication of heat. The temperature of bodies heated by it can 
never be raised above 212°; so that it is much preferable to an open fire for 
heating extracts and organic substances, all danger of. empyreuma being 
avoided. When applied to the cooking of food, the steam is generally passed 
into a shallow tin box, in the upper surface of which are cut several round 
apertures, of such sizes as admit exactly the pans with the materials to be 
heated. The pans are thus surrounded by steam, which condenses upon 
them with great rapidity, till their temperature rises to within a degree or two 



VAPORIZATION. 61 

of 212°. For some purposes, a pan containing- the matters to be heated is 
placed within another and similar larger one, and steam admitted between the 
two vessels. Manufactured goods also are often dried by passing them once 
over a series of metallic cylinders, or square boxes filled with steam. Facto- 
ries are now very generally heated by steam, conveyed through them in cast 
iron pipes. It has been found by practice that the boiler to produce steam for 
this purpose, must have one cubic foot of capacity for every 2000 cubic feet 
of space to be heated to a temperature of 70° or 80°; and that of the con- 
ducting steam pipe, one spare foot of surface must be exposed for every 
200 cubic feet of space to be heated. 

The expansion of water into steam is used as a moving power in the steam 
engine. The application is made upon two different principles, both of which 
may be illustrated by the little instrument depicted on p IG jg 

the margin. It consists of a glass tube, about an inch 
in diameter, slightly expanded into a bulbous form at 
one extremity, and open at the other; a piston is made, 
by twisting tow about the end of a piece of straight 
wire which must be fitted tightly in the tube by the 
use of grease. Upon heating a little water in the bulb 
below the piston, steam is generated, which raises the 
piston to the top of the cylinder. Here the simple 
elastic force of trie steam is the moving power; and in 
this manner steam is employed in the high pressure 
engine. The greater the load upon the piston, and 
the more the steam is confined, the greater does its 
elastic force become. Again, the piston being at the 
top of the cylinder, if we condense the steam with 
which the cylinder is filled, by plunging the bulb into 
cold water, a vacuum is produced below the piston, 

which is now forced down to the bottom of the cylinder by the pressure of 
the atmosphere. In this second part of the experiment, the power is ac- 
quired by the condensation of the steam, or the production of a vacuum; and 
this is the principle of the common condensing engine. In the first efficient 
form of the condensing engine (that of Newcomen) the steam was condensed 
by injecting a little cold water below the piston, which then descended, from 
the pressure of the atmosphere upon its upper surface, exactly as in the instru- 
ment. But Mr. Watt introduced two capital improvements into the construc- 
tion of the condensing engine; the first was, the admitting steam, instead of 
atmospheric air, to press down the piston through the vacuous cylinder, which 
steam itself could afterwards be condensed, and a vacuum be produced above 
the piston, of which the same advantage mi^ht be taken as of the vacuum 
below the piston. The second was, the effecting the condensation of the 
steam, not in the cylinder itself, which was thereby greatly cooled, and occa- 
sioned the waste of much steam in being heated again at every stroke, but in 
a separate air-tight vessel, called the condenser, which is kept cool and va- 
cuous. Into this condenser, the steam is allowed to escape from above and 
from below the piston alternately, and a vacuum is obtained without ever re- 
ducing the temperature of the cylinder below 212°. 

A third and more recent improvement in the employment of steam as a 
moving power, consists in using it expansively, a mode of application which 
will be best understood by being explained in a particular case. Let it be 
supposed that a piston loaded with one ton, is raised four feet by filling the 
cylinder in which it moves with low-pressure steam, or steam of the tension" 
of one atmosphere. An equivalent effect may be produced at the same ex- 
pense of steam, by filling one-fourth of the cylinder with steam of the tension 
6 




62 



VAPORIZATION. 



Fig. 


20. 

11 ' 


4 




3 




9 


2..... 






1 




11 







or 1 atmos. 



|or 2 



. 4 atmos. 



Fig. 21. 



of four atmospheres, and loading the piston 
with four tons, which will be raised one foot. 
But the piston being raised one foot by 
steam of four atmospheres, and in the position 
represented in the figure, the supply of steam 
may be cut off, and the piston will continue 
to be elevated in the cylinder by the simple 
expansion of the steam below it, although 
with a diminished force. When the piston 
has been raised another foot in the cylinder, 
or two feet from the bottom, the volume of 
the steam will be doubled, and its tension 
consequently reduced from four to f , or two 
atmospheres. At a height of three feet in 
the cylinder, the piston will have steam below 
it of the tension of f or If atmosphere, and 
when the piston is elevated four feet, or 
reaches the top of the cylinder, the tension 
of the steam below it will still be -J or one at- 
mosphere. The piston has, therefore, been raised to a height of three feet, 
with a force progressively diminishing from four atmospheres to one, or with 

an average force of two atmospheres , 
by means of a power acquired with- 
out any consumption of steam, but 
by the expansion merely of steam 
that had already produced its usual 
effect. 
The boiler used to produce the steam 
is constructed of different forms. 
The common wagon boiler is repre- 
sented in Figure 21. The heated air 
from the fire below the boiler, after 
passing under its whole length, is 
brought back, before passing to the 
chimney, by flues, o, o, in order that 
what heat the air still contains, may 
be imparted to the sides of the boiler. 
The water is supplied in proper 
quantity to the boiler, and kept at a 
constant level from a fountain-head g, by a tube descending into the boiler 

from a box above it c v. The mouth 
of this tube is closed by a valve, which 
is kept shut by pressure from the 
lever a b, loaded at a. But to the other 
limb b e of the lever an iron rod is at- 
tached, which descends into the boiler, 
and is fixed to a piece of wood/, which 
floats upon the surface of the water. 
When the level of the water is lowered, 
/ falls with it, and occasions the valve 
above to be opened and water to flow 
into the boiler. 

The cylinder boiler, of which a sec- 
tion is given in Figure 22, is preferred 
as the most economical, for the greaj 




Fig. 22. 




VAPORIZATION. 



63 



Fig. 23. 



steam-engines at the Cornish mines. It consists of two cylinders, one within 
the other, the smaller cylinder containing the fire, and the space between the 
two cylinders being occupied by the water. The outer cylinder may be six 
feet in diameter, and is often fifty or sixty feet in length. The heated air 
from the fire, after traversing the inner cylinder is conducted under the boiler 
by the flues o, 0, before it is conveyed to the chimney. 

In locomotive steam-engines, where the 
principal object is to generate steam in a small 
and compact apparatus with great rapidity, a 
different construction is adopted. Here the 
boiler consists of two parts, a square box with 
a double casting, of which a section is given in 
Figure 23, which contains the fire, surrounded 
by water in the space between the casings; and 
a cylinder a, through the lower part of which 
pass a number of copper tubes of small size, 
which communicate at one end with the fire- 
box, and at the other with the chimney, and 
form a passage for the heated air from the 
fire to the chimney. By means of these tubes, 
the object is accomplished of exposing to a 
source of heat, the greatest possible quantity 
of surface in contact with the water. — (See 
Dr. Lardner on the Steam-Engine, Cabinet 
Cyclopedia.) 

The subject of distillation is a natural sequel to vaporization; but it is un- 
necessary to enter into much detail. The principal point to be attended to is 
the most efficient mode of condensing the vapour. Figure 24, represents the 




Fig. 24. 



ordinary arrangement in distilling a liquid 
from a retort a, and condensing the vapour 
in a glass flask b, which is kept cool by 
water dropping upon it from a funnel above 
c. The condensing flask is covered by bi- 
bulous paper, so that the water falling upon 
it may be made to pass equably over its 
surface, and it is supported in a basin like- 
wise containing cold water. 

But a much superior instrument to the 
condensing flask is the condensing tube of 
Professor Liebig, (Figure 25.) This is a C 
plain glass tube, / / about eighteen inches 
in length, and two-thirds of an inch internal 
diameter, which is enclosed in a larger tube, 
b, of brass or tin-plate, about twelve inches 
long and two inches in diameter, the ends 
of which are closed by perforated corks. A constant supply of cold condens- 
ing water from a vessel a is introduced into the space between the two tubes, 




64 



VAPORIZATION. 



Fig. 25. 




being conveyed to the lower part of the instrument by the funnel and tube/, 
and flowing out from the upper part by the tube g. The condensed liquid 
drops quite cool from the low extremity of the glass tube, where a 
vessel is placed to receive it. This is an admirable apparatus, and ought to 
supersede all other means of condensation in the laboratory. The spiral cop- 
per tube or worm which is used for condensing in the common still, is com- 
monly made longer than is necessary, and from its form cannot be examined 
and cleaned like a straight tube. Much vapour may be condensed by a small 
extent of surface, provided it is kept cold by an ample supply of condensing 
water. 



Fig. 26. 




Both the outer and inner tube 
may be of glass in the con- 
densing apparatus which has 
been described, and then the 
small tubes to bring and carry 
off the condensing water, may- 
be made to pass through open- 
ings in the corks, which they fit, 
as represented in Figure 26. 
Evaporation in vacuo. Water rises rapidly into vapour in a vacuous space, 
without the appearance of ebullition, at all temperatures, even at 32°, and 
greatly lower. Its elastic force increases as the temperature is elevated, till at 
212°, it is equal to that of the atmosphere, or capable of supporting a column 
of mercury thirty inches in height. Various other solid and liquid substances 
emit vapour in similar circumstances, such as camphor, alcohol, ether, and oil 
of turpentine. Such bodies are said to be volatile, and other bodies, such as 



VAPORIZATION, 



65 



Fig. 
4 3 



,27. 
2 1 



marble, the metals, &c. which do not emit a sensi- 
ble vapour at the temperature of the air, are said to 
be fixed. All bodies which boil at low temperatures 
belong to the volatile class. An accurate estimate of 
the volatility of different bodies is obtained by deter- 
mining the elastic force of the vapour which they 
emit in the vacuous space above the column of mer- 
cury of the barometer. If we pass up a bubble of air 
into the vacuum of the barometer, above the mer- 
curial column, standing at the time at a height of 30 
inches, the mercury is depressed, we may suppose to 
the level of 29 inches, or by one inch. This would 
indicate that the air, by rising above the mercury, has 
been expanded into thirty times its former bulk, or 
that the elastic force of this rare air is equal to a co- 
lumn of one inch of mercury. The elastic force of 
vapour is estimated in the same manner. A few drops 
of the liquid operated upon are passed up into the 
vacuum above the mercurial column which is depressed 
in proportion to the elastic force of the vapour. The 
depression produced by various liquids is very diffe- 
rent, as illustrated in the annexed figure, representing 
four barometer tubes, in which the mercury is at its 
proper height in No. 1; is depressed by the vapour 
of water of the temperature 60° in No. 2; and by 
alcohol and ether at the same temperature in Nos. 3 
and 4 respectively. 

The depression of the mercurial column produced by water at every degree 
of temperature, between 32° and 212°, was carefully determined by Dr. Dalton, 
and his results have been confirmed by Dr. Ure. The following selected observa- 
tions prove that the elasticity increases at a very rapid rate with the temperature 
Tension of the vapour of water in inches of mercury. Temperature. 

0.2 inch at . . . . .32° 



0.263 

0.375 

0.524 

0.721 

1 

1.36 

1.86 

7.42 

23.64 

30 



40 

50 

60 

70 

80 

90 

100 

150 

200 

212 



The vapours of other liquids increase in density and elastic force with the 
temperature, as well as the vapour of water; but each vapour appears to follow 
a rate of progression peculiar to itself. 

The assumption of latent heat by such vapours is evinced in some processes 
for producing cold. Water may be frozen by the evaporation of ether in the 
air-pump, and a cold produced of 55 degrees under the zero of Fahrenheit by 
the evaporation of that fluid. The ether-vapour derives its store of latent heat 
from the remaining fluid, and contiguous bodies, which are robbed of their 
heat, and suffer a great refrigeration. To sustain the evaporation of this fluid, 
it is necessary to withdraw the vapour as it is produced by continual pumping 
The volatile liquid, sulphuret of carbon, substituted for ether, produces evei* 
greater effects. 

6* 



6^ * 



$® VAPORIZATION. 

On the same principle it founded Leslie's elegant process for the freezing 
of water by its own evaporation, within the exhausted receiver of an air-pump, 
the evaporation being kept up by the absorbent power of sulphuric acid. A 
little water, in a cup of porous stone-ware, is supported over a shallow basin 
containing sulphuric acid. All that is necessary is to produce a good exhaus- 
tion at first: the process of evaporation and absorption then go "on spontane- 
ously, in an uninterrupted manner. Various bodies, which have a powerful 
attraction for watery vapour, may be used as absorbents, such as parched oat- 
meal, the powder of mouldering whinstone, and even dry sole-leather, by 
means of any one of which a small quantity of water may be frozen, during 
summer, in the exhausted receiver of an air-pump. No substance, however, 
is superior, in this respect to concentrated sulphuric acid. When this liquid 
becomes too dilute to act powerfully as an absorbent, it may be rendered again 
fit for use, by boiling it and driving off the water. Ice might be procured in 
quantity, in a warm climate, by this process. The necessary vacuum would 
be most easily commanded, on the large scale, by allowing the receivers to 
communicate with a strong drum, filled with steam, which could be con- 
densed. 

In the Cryophorus of Dr. Wollaston, water is also frozen by its own evapo- 
ration. This instrument consists of two glass bulbs, connected by a tube, and 

containing a portion of water, as 
* IG * "°* represented in the figure. The 

air is first entirely expelled from 
the instrument by boiling the 
water, in both bulbs, at the same 
time, and allowing the steam to 
escape by a small opening at the 
extremity of the little projecting tube e. While the instrument is entirely filled 
with steam, the point of e is fused by the blow-pipe flame, and the opening 
hermetically closed. In experimenting with this instrument, the water is all 
poured into one bulb, and the other or empty bulb placed in a basin containing 
a freezing mixture of ice and salt. The vapour in the cooled bulb is con- 
densed, but its place is supplied by vapour from the water in the other bulb. 
A rapid evaporation takes place in the water bulb, and condensation in the 
empty bulb, till the water in the former bulb is cooled so low as to freeze. The 
instrument derives its name of the cryophorus, or frost-bearer, from this trans- 
ference of the cold of the bulb in the freezing mixture to the bulb at a distance 
from it. 

It is by the evaporation of liquefied carbonic acid, that Thilorier produces the 
extreme depression of temperature, — 148°, which he has attained and measured. 
He allows a small stream of liquid carbonic acid to escape, from a magazine of 
the liquid, into a cylindrical box of wood, like a round snufT box in shape. 
The stream of liquid, which immediately becomes in part gas, is made, as it 
enters the box, to strike against a plain surface at such an inclination as to cause 
the gas to circulate around the circumference of the cavity of the box, instead of 
traversing it in a straight line. The box is speedily filled with a light powder, 
having the appearance of snow, which is solid carbonic acid, one portion of 
the liquid carbonic acid being frozen by the evaporation of the other. The 
solid carbonic acid is an imperfect conductor of heat, and is on that account 
not immediately dissipated by evaporation. It is most conveniently applied 
as a frigorific agent when mixed with ether; with which it forms a soft mass, 
like half-melted snow. Mercury may be frozen in large quantity, by throw- 
ing a portion of this compound upon the surface of the fluid metal. The ether 
evaporates as well as the carbonic acid, and contributes to pioduce the cold, 
To form the liquid carbonic acid itself in large quantity, M. Thilorier makes 



VAPORIZATION. 67 

use of two strong cylindrical vessels of wrought iron, like mercury vessels in 
size and form, one of which is called the generator, and the other the receiver* 
The generator is lined with lead, and is intended for the reception of strong 
muriatic acid and marble, the materials for the production of the gas. It is 
connected with the receiver by a short iron pipe, which is provided with a 
stop-cock, so that the receiver can be separated from the generator, without 
loss of gas from the former. The generator is charged with materials several 
times in succession, and the product accumulated in the receiver till it may 
amount to a pound or two. The stop-cock and screws in this apparatus must 
be of the most accurate workmanship, and be screwed down upon leaden, 
washers. 

The question arises, do those bodies which evaporate at a moderate tempe- 
rature continue to evaporate at all temperatures, however low? The opinion 
has prevailed, that bodies which are decidedly vaporous at high temperatures y 
such as sulphuric acid and mercury, never cease to evolve vapour, however 
far their temperature may be depressed, although the quantity emitted be- 
comes less and less, till it ceases to be appreciable by our senses. Even fixed 
bodies, such as metals, rocks, &c, have been supposed to allow an escape 
of their substance into air at the ordinary temperature; and hence the at- 
mosphere has been supposed to contain traces of the vapours of all the 
bodies with which it is in contact. Certain researches of Dr. Faraday, pub- 
lished in the Philosophical Transactions for 1826, on the existence of a limit 
to vaporization, established the opposite conclusion. Mercury was found 
to yield a small quantity of vapour during summer, at a temperature varying 
from 60° to 80°, but in winter no trace of vapour could be detected. Dr. Fa- 
raday has proved that several chemical agents, which may be volatilized by a 
heat between 300° and 400°, did not undergo the slightest evaporation when 
kept in a confined space with water during four years. 

Bodies, therefore, cease all at once to emit vapour, at some particular 
temperature. In the case of mercury, this temperature lies between 40° 
and 60° Fahrenheit. But a progressive and endless diminution of vaporizing 
power is certainly more natural than an abrupt cessation. What puts a stop 
to vaporization? it may be asked. Liquids, we know, have a certain attrac- 
tion for their own particles, evinced in their disposition to collect together in 
drops. The particles of solids are attracted more powerfullv, and cohere 
strongly together. Dr. Faraday is of opinion, that when the vaporizing 
power becomes very weak, at low temperatures, it may be overcome and ne- 
gatived completely by this cohesive attraction, and no escape of particles in the 
vaporous form be permitted. 

This supposition is conformable with the views of corpuscular philosophy 
entertained by Laplace. According to that profound philosopher, the form of 
aggregation which a body affects, depends upon the mutual relation of three 
forces: 1. The attraction of each particle for the other particles which surround it, 
which induces them to approach as near as possible to each other. 2. The attrac- 
tion of each particle for the heat which surrounds the other particles in its neigh- 
bourhood. 3. The repulsion between the heat which surrounds each particle, 
and that which surrounds the neighbouring- particles, a force which tends to 
disunite the particles of bodies. When the first of these forces prevails, the 
body is solid; if the quantity of heat augments, the second force becomes domi- 
nant, the particles then move among each other with facility, and the body is 
liquid. While this is the case, the particles are still retained by the attrac- 
tion for the neighbouring heat, within the limits of the space which the body 
formerly occupied, except at the surface, where the heat separates them, that 
is to say, occasions evaporation, till the influence of some pressure prevents 
the separation from being effected. When the heat increases to such a de- 




68 VAPORIZATION. 

gree that the reciprocal repulsive force prevails over the attraction of the par- 
ticles for one another, they disperse in all directions, as long as they meet no 
obstacle, and the body assumes the gaseous form. Berzelius adds "the reflec- 
tion, that if, in that gaseous state, into which Cagnard de la Tour reduced 
some volatile liquids, the pressure does not correspond with the result of cal- 
culation, that difference may depend on this: that, as the particles have not an 
opportunity to recede much, the first two forces continue always to act, 
and oppose the tension of the gas, which does not establish itself in all its 
power unless when the particles are so distant from each other as to be out of 
the sphere of the influence of these forces.* 

Gases. Permanent gases, such as atmospheric air, unquestionably owe their 
elastic state to the possession of latent heat. But the theory of the similar 
constitution of gases and vapours, although supported by strong analogies, 
was not generally adopted by chemists, till it was experimentally confirmed 
by Dr. Faraday, who liquefied several of the gases.t His method was to ge- 
-p op nerate the gas in one end of a strong 

glass tube, bent in the middle, as re- 
presented in the figure, and hermeti- 
cally sealed. The gas accumulating 
in a confined space, comes to exert a 
prodigious pressure, an effect of which 
is, that a portion of the gas itself condenses into a liquid in the end of the tube 
most remote from the materials, which is kept cool with that view. Consi- 
derable danger is to be apprehended by the operator in conducting such expe- 
riments, from the bursting of the glass tubes, and the face ought always to be 
protected by a wire-gauze mask from the effects of an explosion. The names 
of the gases which were liquefied in this manner, are sulphurous acid, cyanogen, 
chlorine, ammoniacal gas, sulphuretted hydrogen, carbonic acid, muriatic acid, 
and nitrous oxide; which required a degree of pressure varying, in the diffe- 
rent gases, from two atmospheres, in the first-mentioned, to fifty atmospheres, 
in the last-mentioned gas, at the temperature of 45°. The liquefaction of se- 
veral of these gases has since been effected by the application of cold alone, 
without compression. 

The elastic force of the vapours arising from these gases increases at a rapid 
rate with their temperature. Thus the vapour from liquefied ammonia at 32° 
was found to exert a pressure of 5 atmospheres, and when heated to 52°, a pres- 
sure of 65 atmospheres ; the vapour from liquid sulphuretted hydrogen at 3° 
exerted a pressure of 14 atmospheres, and at 47° a pressure of 17 atmospheres. 
Liquid muriatic acid at 32°, 22°, and 47° respectively, exerted a force of 20, 
25, and 40 atmospheres; carbonic acid at 12° and 32°, a force of 20 and 36 
atmospheres. Sir H. Davy threw out the idea that the prodigious elastic force 
of these fluids might be used as a moving power. But supposing the applica- 
tion practicable, it may be doubted, from what we know of the constancy of 
the united sum of the latent and sensible heat of high pressure steam, whether 
any saving of heat would be effected by such an application of the vapours of 
the liquefied gases. 

In certain gases, particularly hydrogen, nitrogen, oxygen, nitric oxide, and 
carburetted hydrogen, compression alone seems inadequate to produce liquefac- 
tion ; for these gases have preserved their elastic form under a pressure of at 
least 800 atmospheres. There can be little doubt, however, that all other gases 
at present known would yield to a less compressing force. Exposure to ex- 
treme cold, with the application of great pressure at the same time, is the most 
likely means of liquefying the more refractory gases. 

* Tratte de Chimie, par. J. J. Berzelius, t. 1, p. 85. 
t Philosophical Transactions, 1123, p. 189. 



GASES. 69 

All gases whatever are absorbed and condensed by water in a greater or 
less degree, in which case they certainly assume the liquid form. The quantity 
condensed is widely different in the different gases ; and in the same gas the 
quantity condensed depends upon the pressure to which the gas is subjected, 
and the temperature of the absorbing water. In the case of carbonic acid gas 
Dr. Henry proved that the volume absorbed by water is the same, whatever be 
the pressure to which the gas is subject. Hence, we double the weight or 
quantity of gas absorbed by subjecting it, in contact with water, to the pressure 
of two atmospheres ; and this practice is adopted in impregnating water with 
carbonic acid, to make soda-water. The colder the water, the greater also the 
quantity of gas absorbed. 

In the physical theory of gases, they are assumed to be expansible to an in- 
definite extent, in the proportion that pressure upon them is diminished, and to 
be contractible under increased pressure exactly in proportion to the compres- 
sing force — the well-known law of Mariotte. The bulk of atmospheric air has 
been found rigidly to correspond with this law, when it was expanded into 300 
volumes, and also when compressed into l-25th of its primary volume. But 
there is reason to doubt whether the law holds with absolute accuracy, in the 
case of a gas either in a state of extreme rarefaction, or of the greatest density. 
Thus atmospheric air does not appear to be indefinitely expansible ; for there is 
certainly a limit to the earth's gaseous atmosphere, and it does not expand into 
all space. Dr. Wollaston supposed that the material particles of air are not 
indefinitely minute, but have a certain magnitude and weight. These particles 
are under the influence of a powerful mutual repulsion, as is always the case 
in gaseous bodies, and therefore, tend to separate from each other ; but as this 
repulsive force diminishes as the distance of the particles from each other in- 
creases, Dr. Wollaston imagined that the weight of the individual particles might 
come at last to balance it, and thus prevent their farther divergence. On this 
view, which is exceedingly probable, the expansion of a gas, caused by the re- 
moval of pressure, will cease at a particular stage of rarefaction, and the gas 
not expanding farther, will come to have an upper surface, like a liquid. The 
earth's atmosphere has probably an exact limit, and true surface. 

The deviation from the law of Mariotte, in the case of gases under a greater 
pressure than that of the atmosphere, has been distinctly observed in the more 
liquefiable gases. Thus, Professor Oersted, of Copenhagen, found that sulphur- 
ous acid gas diminishes, under increased pressure, more rapidly than common 
air. The volumes of atmospheric air and of the gas were equal at the following 
pressures : 

Pressure upon air in Pressure upon sulphurous 

atmospheres. gas in atmospheres. 

1 1 

1.175 ...... 1.173 

2.821 . . . . . 2.782 

3.319 . . . . . . 3.189 

It will be observed that less pressure always suffices to reduce the sulphurous 
acid gas to the same bulk than is required by air. If the pressure upon the air and 
gas were made equal, then the gas would be compressed into less bulk than the 
air, and deviate from the law of Mariotte. Despretz has more lately observed 
an equally conspicuous deviation from this law under increasing pressures, in 
several other gases, particularly sulphuretted hydrogen, cyanogen, and ammo- 
nia, which are all easily liquefied. There is no reason, however, to suppose that 
any partial liquefaction of the gases occurs under the pressure applied to them 
in such experiments. They remain entirely gaseous, and their superior com- 
pressibility, must be referred to a law of their constitution. It is the phenome- 
non beginning to show itself in a gas under moderate pressure, which was 



70 



VAPORIZATION. 



observed in all its excess by Cagnard de la Tour, in the vapours confined by 
him under great pressure, (page 59.) 

Those gases, which exhibit this deviation, must occupy less bulk than they 
ought to do under the pressure of the atmosphere itself; which may be the 
reason why the liquefiable gases are generally found by experiment to be spe- 
cifically heavier than they ought by theory to be. 

Such are the most remarkable features which gases exhibit in relation to 
pressure and temperature. These properties are independent of the specific 
weights of the gases, which are very different in the various members of the 
class, and they are but little connected with the nature of the particular sub- 
stance or material which exists in the gaseous form. But when different gases 
are presented to each other, a new property of the gaseous state is developed, 
namely the forcible disposition of different gases to intermix, or to diffuse 
themselves through each other. This is a property which interferes in a great 
variety of phenomena, and is no less characteristic of the gaseous state than 
any we have considered. It may be treated of under the head, 1° of the dif- 
fusion of gases through each other, and 2° of the diffusion of vapours into 
gases, by which is meant, the ascent of vapours from volatile bodies into air 
and other gases, of which the spontaneous evaporation of water into the air is 
an instance. 

Diffusion of gases. When a light and heavy gas are once mixed together, 
they do not exhibit any tendency to separate again, on standing at rest for 
some time, differing in this respect from mixed liquids, many of which speedily 
separate, and arrange themselves according to their densities, the lightest up- 
permost, and the heaviest undermost, as in the familiar example of oil and 
water, unless they have combined together. This peculiar property of gases 
has repeatedly been made the subject of careful experiment. Common air, 
for instance, is essentially a mixture of two gases, differing in weight in the 
proportion of 976 to 1 103, but the air in a tall close tube of glass several feet 
in length, kept upright in a -still place, has been found sensibly the same in 
composition at the top and bottom of the tube, after a lapse of months. Hence, 
there is no reason to imagine that the upper strata of the air differ in compo- 
sition from the lower ; or that a light gas, such as hydrogen, escaping into the 
atmosphere will rise, and ultimately possess the higher regions ; suppositions 
which have been made the groundwork of meteorological theories at different 
times. 

The earliest observations we possess on this subject are those of Dr. Priestley, 
Fig. 30. t0 whom pneumatic chemistry stands so much indebted. Having 
f repeated occasion to transmit a gas through stoneware tubes sur- 
rounded by burning fuel, he perceived that the tubes were porous, 
and that the gas escaped outwards into the fire, while at the same 
time the gases of the fire penetrated into the tube, although the gas 
within the tube was in a compressed state. 

Dr. Dalton, however, first perceived the important bearjngs of this 
property of aerial bodies, and made it the subject of experimental in- 
quiry. He discovered that any two gases, allowed to communicate 
with each other, exhibit a positive tendency to mix or to penetrate 
through each other, even in opposition to the influence of their weight. 
Thus, a vessel containing a light gas (hydrogen,) being placed above 
a vessel containing a heavy gas (carbonic acid,) and the two gases 
allowed to communicate by a narrow tube, as represented in the 
figure, an interchange speedily took place of a portion of their con- 
tents, which it might have been supposed that their relative position 
would have prevented. Contrary to the solicitation of gravity, the 
heavy gas continued spontaneously to ascend and the light gas to 



DIFFUSION OF GASES. 71 

descend, till in a few hours they became perfectly mixed, and the proportion of 
the two gases was the same in the upper and lower vessels. This disposition 
of different gases to intermix, appeared to Dr. Dalton, so decided and strong, 
as to justify the inference that different gases afford no resistance to each other ; 
but that one gas spreads or expands into the space occupied by another 
gas, as it would rush into a vacuum. At least, that the resistance which 
the particles of one gas offer to those of another is of very imperfect kind, to be 
compared to the resistance which stones in the channel of a stream opposes 
to the flow of running water. Such is Dr. Dalton's theory of the miscibility 
of the gases. (Manchester Memoirs, vol. 5.) 

In entering into this inquiry I found, first, that gases diffuse into the atmo- 
sphere and into each other, with different degrees of ease and rapidity. This 
was observed by allowing each gas to diffuse from a bottle into the air through 
a narrow tube, taking care, when the gas was lighter than air, that it was al- 
lowed to escape from the lower part of the vessel, and when heavier from the 
upper part, so that it had, on no occasion, any disposition to flow out, but was 
constrained to diffuse in opposition to the effect of gravity. The result was, 
that the same quantity of different gases escapes in times which are exceedingly 
unequal, but have a relation to the specific gravity of the gas. The light gases 
diffuse or escape most rapidly ; thus, hydrogen escapes five times quicker than 
carbonic acid, which is twenty-two times heavier than that gas. Secondly, in 
the case of an intimate mixture of two gases, the most diffusive gas separates 
from the other, and leaves the receiver in the greatest proportion. Hence, by 
availing ourselves of the tendencies of mixed gases to diffuse with different de- 
grees of rapidity, a sort of mechanical separation of gases may be effected. The 
mixture must be allowed to diffuse for a certain time into a confined gaseous 
or vaporous atmosphere, of such a kind as may afterwards be condensed or ab- 
sorbed with facility.* 

But the nature of the process of diffusion is best illustrated when the gases 
communicate with each other through minute pores or apertures of insensible 
magnitude. 

A singular observation belonging to this subject was made by Professor Do- 
bereiner of Jena, on the escape of hydrogen gas by a fissure or crack in glass 
receivers. Having occasion to collect large quantities of that light gas, he had 
accidentally made use of a jar which had a slight fissure in it. He was sur- 
prised to find that the water of the pneumatic trough rose into this jar, one and 
a half inches in twelve hours; and that after 24 hours, the height of the water 
was two inches two thirds above the level of that in the trough. During the ex- 
periment, neither the height of the barometer, nor the temperature of the place 
had sensibly altered, f He ascribed the phenomenon to capillary action, and 
supposed that hydrogen only is attracted by the fissures, and escapes through 
them on account of the extreme smallness of its atoms. It is unnecessary to 
examine this explanation, as Dobereiner did not observe the whole phenome- 
non. On repeating the experiment, and varying the circumstances, it appeared 
to me that hydrogen never escapes outwards by the fissure without a certain 
portion of air penetrating at the same time inwards, amounting to between one- 
fourth and one-fifth of the volume of the hydrogen which leaves the receiver. It 
was found by an instrument, which admits of much greater precision than the 
fissured jar, that when hydrogen gas communicates with air through such a 
chink, the air and hydrogen exhibit a powerful disposition to exchange places 
with each other; a particle of air, however, does not exchange with a particle of 
hydrogen of the same magnitude, but of 3.83 times its magnitude. We may 

* Quarterly Journal of Science, New Series, Vol. V. 
t Annates de Chimie et de Physique, 1825. 



72 



VAPORIZATION. 



) 



7 



adopt the word diffusion-volume, to express this diversity of disposition in gases 
to interchange particles, and say that the diffusion-volume of air being 1, that of 
hydrogen gas is 3.83. Now every gas has a diffusion-volume peculiar to itself, 
and depending upon its specific gravity. Of those gases which are lighter than 
air, the diffusion- volume is greater than 1, and of those which are heavier, the 
diffusion-volume is less than i .* 

Exact results are obtained by means of a simple instrument, which may be 
called a diffusion tube, and which is constructed as follows. A glass tube, open 
at both ends, is selected, half an inch in diameter, and from six to fourteen inches 
in length. A cylinder of wood, somewhat less in diameter, is introduced into 
the tube so as to occupy the whole of it, with the exception of about one-fifth of 
an inch at one extremity, which'space is filled with a paste of Paris plaster, of the 
usual consistence for casts. In the course of a few minutes the plaster sets, and 
on withdrawing the wooden cylinder, the tube forms a receiver, closed by an 
immoveable plate of stucco. In the wet state, the stucco is air-tight ; it is there- 
fore dried, either by exposure to the air for a day, or by placing it in a tempe- 
rature of 200° for a few hours ; and is thereafter found to be permeable by gases, 
Fig. 32. Fig. 31. even m tne most humid atmosphere, if not po- 

sitively wetted. When such a diffusion-tube, 
six inches in length, is filled with hydrogen 
over mercury, the diffusion, or exchange of air 
for hydrogen, instantly commences through 
the minute pores of the stucco, and proceeds 
with so much force and velocity, that within 
three minutes, the mercury attains a height in 
the receiver of more than two inches above its 
level in the trough ; within twenty minutes, the 
whole of the hydrogen has escaped. In con- 
ducting such experiments over water, it is ne- 
cessary to avoid wetting the stucco. With 
this view, before filling the diffusion tube with 
hydrogen, the air is withdrawn by placing the 
tube upon the short limb of an empty syphon, 
(see Figure 31,) which does not reach, but 
comes within half an inch of the stucco, and 
then sinking the instrument in the water 
trough, so that the air escapes by the syphon, 
with the exception of a small quantity, which 
is noted. The diffusion tube is then filled up, 
either entirely or to a certain extent, with the 
gas to be diffused. 
The ascent of the water in the tube, when hydrogen is diffused, forms a 
striking experiment. But in experiments made with the purpose of determin- 
ing the proportion between the gas diffused and the air which replaces it, it 
is necessary to guard against any inequality of pressure, by placing the diffu- 
sion tube in ajar of water as in Figure 32, and filling the jar with water in pro- 
portion as it rises in the tube.t 

* The mathematical relation which subsists between the diffusion-volume, and the den- 
sity of a gas is expressed thus : 

Diffusion-volume = — 

dk 

where d represents the specific gravity of the gas. 

t A diffusion experiment affords the elements for calculating the specific gravity of a gai. 

/A\ 2 
The specific gravity sf- ) 



DIFFUSION OF GASES. 73 

In this instrument we may substitute many other porous substances for the 
stucco; but few of them answer so well. Dry and sound cork is very suita- 
ble, but permits the diffusion to go on very slowly, not being sufficiently po- 
rous; so do thin slips of many granular foliated minerals, such as flexible mag- 
nesian limestone. Charcoal, woods, unglazed earthenware, dry bladder, may 
all be used for the same purpose. 

A slight deviation from the law is observed in gases which differ in a certain 
physical property from air, namely, in the greater facility with which they may 
be forced through pores or minute apertures by pressure. A dissimilarity be- 
tween the gases, in this respect, had long been recognised, although no accu- 
rate experiments had been made on the subject It became, however, neces- 
sary to examine this point. A small bell-jar, with a short neck and opening 
at the top, was used, which opening was closed by a plate of stucco half an inch 
in thickness, over which a brass cap and stopcock were fitted and cemented. 
This receiver was placed on the plate of an air-pump in perfect order, and ex- 
hausted. When the stopcock was closed, nothing entered the exhausted receiver; 
but on opening it, either air entered, forcing its way through the pores of the 
stucco, or any gas which might be conducted to it, by means of a flexible tube 
from a proper magazine. Gas was allowed to enter till it acquired a pressure 
of three inches, always setting out with air of the tension of one inch mercury 
in the receiver. 

The same quantity of different gases entered in the following times: 
Air, dry . . . . . . in 10' 

Air, saturated with moisture, at 60° . . .10' 

Carbonic acid . . . . . .10' 

Nitrogen . . . . . .10' 

Oxygen . . . . . .10' 

Carbonic oxide . . . . . 9' 30" 

Olefiant gas . . . . 7' 50 

Coal gas . . . .7' 

Hydrogen ...... 4' 

Hydrogen, therefore, entered under pressure 2.4 times, or nearly 2% times 
quicker than air, while several gases had the same rate as air. Those gases 
which percolate very easily, enter the diffusion instrument somewhat in excess, 
particularly when the plate of stucco is thin. The deviation is perceptible in 
hydrogen, and olefiant gas, and is also very sensible in coal gas and carburetted 
hydrogen. 

It can be shown, on the principles of pneumatics, that gases should rush into a 
vacuum with velocities corresponding to the numbers which have been found 
to express their diffusion volumes; that is, with velocities inversely propor- 
tional to the square root of the densities of the gases. The law of the diffusion 
of gases has on this account been viewed by my friend, Mr. T. S. Thompson, 
of Clitheroe, as a conformation of Dr. Dalton's theory, that gases are inelastic 
towards each other.* It must be admitted that the ultimate result in diffusion 
is in strict accordance with Dalton's law, but there are certain circumstances 
which make me hesitate in adopting it as a true representation of the pheno- 
menon, although it affords a convenient mode of expressing it. 1. It is sup- 
posed, on that law, that when a cubic foot of hydrogen gas is allowed to com- 
municate with a cubic foot of air, the hydrogen expands into the space occu- 
pied by the air, as it would do into a vacuum, and becomes two cubic feet of 
hydrogen of half density. The air, on the other hand, expands in the same 

where G is the measure of gas submitted to diffusion, and A the measure of return air. — 
Edinb. Phil. Trans. XII, 222; or Phil. Mag. 3rd series, II. 175. 
* Phil. Mag. 3rd series, IV. 321. 
7 



74 DIFFUSION OF GASES. 

manner into the space occupied by the hydrogen, so as to become two cubic 
feet of air of half density. Now if the gases actually expanded through each 
other in this manner, cold should be produced, and the temperature of the 
mixed gases should fall 40 or 45 degrees. But not the slightest change of 
temperature occurs in diffusion, however rapidly the process is conducted. 
2. Although the ultimate result of diffusion is always in conformity with Dal- 
ton's law, yet the diffusive process takes place in different gases with very 
different degrees of rapidity. Thus, the external air penetrates into a diffu- 
sion tube with velocities denoted by the following numbers, 1277, 623, 302, 
according as the diffusion tube is filled with hydrogen, with carbonic acid, 
or with chlorine gas Now, if the air were rushing into a vacuum in all these 
cases, why should it not always enter it with the same velocity? Something 
more, therefore, must be assumed than that gases are vacua to each other, 
in order to explain the whole phenomena observed in diffusion. 

Passage of gases through membranes. In connexion with diffusion, the 
passage of gases through humid membranes may be noticed. If a bladder, 
half filled with air, with its mouth tied, be passed up into a large jar filled with 
carbonic acid gas, standing over water, the bladder, in the course of twenty-four 
hours becomes greatly distended, by the insinuation of the carbonic acid 
through its substance, and may even burst, while a very little air escapes out- 
wards from the bladder. But this is not simple diffusion. The result depends 
upon two circumstances; first, upon carbonic acid being a gas easily liquefied 
by the water in the substance of the membrane, — the carbonic acid penetrates 
the membrane as a liquid; secondly, this liquid is in the highest degree volatile, 
and, therefore, evaporates very rapidly from the inner surface of the bladder 
into the air confined in it. The air in the bladder comes to be expanded in 
the same manner as if ether or any other volatile fluid was admitted into it. 
The phenomenon was observed by Dalton in its simplest form. Into a very 
narrow jar, half filled with carbonic acid gas over water, he admitted a little 
air. The air and gas were accidentally separated by a water bubble, and thus 
prevented from intermixing. But the carbonic gas immediately began to be 
liquefied by the film of water, and passing through it, evaporated into the air 
below. The air was in this way gradually expanded, and the water bubble 
ascended in the tube. Here the particular phenomenon in question was ob- 
served to take place, but without the intervention of membrane. It is to be 
remembered that the thinnest film of water or any liquid is absolutely imper- 
meable to a gas as such. 

In the experiments of Drs. Mitchell and Faust and others, in -which gases 
passed through a sheet of caoutchouc, it is to be supposed that the gases were 
always liquefied in that substance, and penetrated through it in a fluid form. 
Indeed few bodies are more remarkable than caoutchouc for the avidity with 
which they imbibe various liquids. The absorption of ether, of naphtha, of 
oil of turpentine, which soften the substance of the caoutchouc, without dis- 
solving it, may be referred to. It is likewise always those gases which are 
most easily liquefied by cold or pressure that pass most readily through both 
caoutchouc and humid membranes. Dr. Mitchell found that the time required 
for the passage of equal volumes of different gases through the same mem- 
brane, was 

1 minute, with ammonia. 
2| minutes, with sulphuretted hydrogen. 
3| „ cyanogen. 

5£ „ carbonic acid. 

6£ „ nitrous oxide. 

27j „ arsenietted hydrogen. 



DIFFUSION OF VAPOURS. 75 

28 „ defiant gas. 

37| » hydrogen. 

113 „ oxygen. 

160 „ carbonic oxide, 

and a much greater time with nitrogen. 

Diffusion of Vapours into air, or spontaneous evaporation. Volatile bodies, 
such as water, rise into air as well as into a vacuum, and obviously according 
to the law, by which gases diffuse through each other. Thus, if a small quan- 
tity of the volatile liquid ether be conveyed into two small jars standing over 
water, one half filled with air, and the other with hydrogen gas, the air and 
hydrogen immediately begin to expand, from the ascent of the ether-vapour into 
them, and the two gases in the end have their volume increased exactly in the 
same proportion. But the hydrogen gas undergoes this expansion in half the 
time that the air requires ; that is to say, ether-vapour follows the usual law of 
diffusion in penetrating more rapidly through the lighter gas. 

We are indebted to Dr. Dalton for the discovery that the evaporation of 
water has the same limit in air as in a vacuum. Indeed the quantity of vapour 
from a volatile body which can rise into a confined space, is exactly the same, 
whether that space be a vacuum, or already filled with any air or gas, in any 
state of rarefaction or condensation. The vapour rises and adds its own elastic 
force, such as it exhibits in a vacuum, to the elastic force of the other gases or 
vapours already occupying the same space. Hence, it is only necessary to 
know what quantity of any vapour rises into a vacuum at any particular tem- 
perature; — the same quantity rises into air. Thus the vapour from water, 
which rises into a vacuum at 80°, depresses the mercurial column one inch, 
or its tension is one thirtieth of the usual tension of the air. Now, if water 
at 80° be admitted into dry air, it will increase the tension of that air by 
l-30th, if the air be confined; or increase its bulk by l-30th if the air be 
allowed to expand. 

The spontaneous evaporation of water into air is much affected by three cir- 
cumstances: 1°. the previous state of dryness of the air, for a certain fixed 
quantity only of vapour can rise into air, as much as into the same space if 
vacuous ; and if a portion of that quantity be already present so much the less 
will be taken up by the air ; and no evaporation whatever takes place into air 
which contains this fixed quantity, and is already saturated with humidity. 2°. 
By warmth, for the higher the temperature the more considerable is the quan- 
tity of vapour which rises into any accessible space. Thus water emits so much 
vapour at 40° as expands the air in contact with it 1-1 14th part, and at 60° 
as much as expands air l-57th part, or double the quantity emitted at the 
lower temperature. Hence, humid hot air contains a much greater portion of 
moisture than humid cold air. 3°. The evaporation of water is greatly quick- 
ened by the removal of the incumbent air in proportion as it becomes saturated ; 
and hence a current of air is exceedingly favourable to evaporation. 

When air saturated with humidity at a high temperature is cooled, it ceases 
to be able to sustain the large portion of vapour which it possesses, and the ex- 
cess assumes the liquid form, and precipitates in drops. Many familiar ap- 
pearances depend upon the condensation of the vapour in the atmosphere. 
When a glass of cold water, for instance, is brought into a warm room, it is 
often quickly covered with moisture. The air in contact with the glass is chilled, 
and its power to retain vapour so much reduced as to occasion it to deposite a 
portion upon the cold glass. It is from the same cause that water is often seen 
in the morning running down in streams upon the inside of the glass panes of 
bed-room windows. The glass has the low temperature of the external air, 
and by contact cools the warm and humid air of the apartment so as to occa- 
sion the precipitation of its moisture. Hence also, when a warm thaw follows 



76 



VAPORIZATION. 



Fig. 33. 



after frost, thick stone walls which continue to retain their low temperature, 
are covered by a profusion of moisture. 

Hygrometers. As water evaporates at all temperatures, however low, the 
atmosphere cannot be supposed to be ever entirely destitute of moisture. The 
proportion present varies with the temperature, the direction of the wind, and 
other circumstances, but is generally greater in summer than in winter. There 
are various means by which the moisture in the air may be indicated and its 
quantity estimated, affording principles for the construction of different hygro- 
scopes or hygrometers. 

1st. Many solid substances swell on imbibing moisture, and contract again 
on drying, such as wood, parchment, hair, and most dry organic substances. 
The hygrometer of Deluc consisted of an extremely thin piece of whalebone, 
which in expanding and contracting moved an index. The principle of this 
instrument is illustrated in the transparent shavings of whalebone cut into fi- 
gures, which bend and crumple up when laid upon the warm hand. Saussure 
made use of human hair boiled in caustic ley, as a hygrometric body, and it 
appears to answer better than any other substance of the class. Instruments 
of this kind are graduated experimentally from observations made on placing 
them in air kept at a known state of dryness by the presence of deliquescent 
salts. But all such instruments alter in their indications after a time, and should 
be viewed as hygroscopes rather than hygrometers. 

2ndly. The degree of dryness of the air may be 
judged of by the rapidity of evaporation. Leslie 
made use of his differential thermometer as a hy- 
grometer, covering one of the bulbs with muslin, 
and keeping it constantly moist by means of a 
wet thread from a cup of water placed near it. 
The evaporation of the moisture cools the ball and 
occasions the air in it to contract. This instrument 
gives useful information in regard to the rapidity of 
evaporation, or the drying power of the air, but 
does not indicate directly the quantity of moisture in 
the air. The wet-bulb hygrometer more common- 
ly used, acts on the same principle, but consists of 
two similar and very delicate mercurial thermome- 
ters, the bulb of one of which a, is kept constantly 
moist, while the bulb of the other b is dry. The 
wet thermometer always indicates a lower tem- 
perature than the dry one, unless when the air is 
fully saturated with moisture and no evaporation 
from the moist bulb takes place. In making an 
observation, the instrument is generally placed, 
not in absolutely still air, but in an open window 
where there is a slight draft. 

3rdly. The most simple mode of ascertaining the absolute quantity of 
vapour in the air, is to cool the air gradually, and note the degree of temperature 
at which it begins to deposite moisture, or ceases to be capable of sustain- 
ing the whole quantity of vapour, which it possesses. The air is saturated 
with vapour for this particular degree of temperature which is called its 
dew-point. The saturating quantity of vapour for the degree of temperature 
indicated, may then be learned by reference to a table of the tension of the va- 
pour of water at different temperatures.* It is the absolute quantity of vapour 
which the air at the time of the observation possesses. The dew-point may 




Such a table will be- given in an Appendix. 



HYGROMETERS. 



77 



Fig. 34. 



be ascertained most accurately by exposing to the air a thin cup of silver or 
tin-plate containing water so cold as to occasion the condensation of dew upon 
the metallic surface. The water in the cup is stirred with the bulb of a small 
thermometer, and as the temperature gradually rises, the degree is noted at 
which the dew disappears from the surface of the vessel. The temperature at 
which this occurs may be taken as the dew-point. Water may always be cooled 
sufficiently in summer, to answer for an experiment of this kind by dissolving 
pounded sal-ammoniac* in it. 

The dew point may be observed much more quickly by means of the elegant 
hygrometer of Professor Daniell.* This instrument (see Figure) consists of two 
balls connected by a syphon and containing a quantity of ether, from which the 
air has been expelled by the same means as in the cryophorus of Dr. Wollaston, 
(page 66). One of the arms of the syphon tube contains a small thermometer, 
with its scale, which should be of white enamel ; the bulb of the thermometer 
descends into the ball b, at the extremity of this arm, and 
is placed, not in the centre of the ball, but as near as 
possible to some point of its circumference. A zone of 
this ball is gilt and burnished, so that the deposition of 
dew may easily be perceived upon it. The other ball a, 
is covered with muslin. When an observation is to be 
made, this last ball is moistened with ether which is sup- 
plied slowly by a drop or two at a time. It is cooled by 
the evaporation of the ether and becomes capable of con- 
densing the vapour of the included fluid, and thereby oc- 
casions evaporation in the opposite ball b, containing 
the thermometer. The temperature of the ball b, should 
be thus reduced in a gradual manner, so that the de- 
gree of the thermometer at which dew begins to be de- 
posited on the metallic part of the surface of the ball may 
be observed with precision. The temperature of b being 
thereafter allowed to rise, the degree at which the dew 
disappears from its surface may likewise be noted. It 
should not differ much from the temperature of the de- 
position, and will probably give the dew point more cor- 
rectly, although, strictly speaking, the mean between 
the two observations should be the true dew point. It is convenient to have a 
second thermometer in the pillar of the instrument, for observing the temperature 
of the air at the time. 

A Jess expensive instrument! is constructed by Mr. Jones of London ,which ap- 
pears to indicate the dew point with tolerable accuracy. It consists of a delicate 
mercurial thermometer, of which the whole bulb, with the exception of about 
one-fourth of its surface, is covered with muslin. The bulb is cooled by the 
application of ether to the coated surface, and the temperature observed at 
which dew first makes its appearance upon the naked part of the bulb. Mr. 
Foggo, of Leith, finds the indications of this instrument to be trustworthy!, but a 
preference is given, by most observers, to the original instrument of Daniell. 

The indications of the wet-bulb hygrometer first described are discovered by 
simple inspection. It is, therefore, a problem of the greatest importance to de- 
duce from them the dew point, or the tension of the vapour in the air, by an 




* Daniell's Meteorological Essays, p. 147. 

t (Invented by M. F.Nollet of Brussels. Journ deChirn. Med. No. IV. t. VIII. Il.Serie. 
The report of the committee appointed to examine this thermo hygrometer speaks in a 
very favourable manner of its merits. R. B.] 

X Brewster's Journal, VII. 36. 

7* 



78 VAPORIZATION. # 

easy rule. Could this inference be made with certainty, the wet-bulb hygro- 
meter is so commodious that it would supersede all others. I shall place below 
the formula of Dr. August, which after constant application for the last ten years, 
has received the general sanction of philosophers of Berlin. It was employed 
by Humboldt and G. Rose in their recent expedition to Siberia, and (as I was as- 
sured by the latter) with excellent effect * 

In evaporating by means of hot air, as in drying goods in the ordinary 
bleacher's stove, which is heated by flues from a fire carried along the floor, it 
should be kept in mind that a certain time must elapse before air is saturated 
with humidity. Mr. Daniell has observed that a few cubic inches of dry air con- 
tinue to expand for an hour or two, when exposed to water at the temperature 
of the air. At high temperatures, the diffusion of vapour into air is more rapid ; 
but still it is not all instantaneous. Hence, in such a drying stove, means ought 
to be taken to repress rather than to promote the exit of the hot air ; otherwise 
a loss of heat will be occasioned by the escape of the air, before it is saturated 
with humidity. The greatest advantage has been derived from closing such a 
stove as perfectly as possible at the top, and only opening it after the goods are 
dried and about to be removed, in order to allow of a renewal of the air in the 
chamber between each operation. In evaporating water by heated air, the 
vapour itself carries off exactly the same quantity of heat as if it were pro- 
duced by boiling the water at 212°, while the air associated with it likewise re- 
quires to have its temperature raised, and therefore occasions an additional 
consumption of heat. Hence water can never be evaporated by air in a drying 
stove with so small an expenditure of fuel as in a close boiler. 

When bodies to be dried do not part with their moisture freely, but in a 
gradual manner, as is the case with roots, and most organic substances, the hot 

* Dr. August's formula for deducing the tension of vapour in the air from the tempera- 
ture indicated by a wet, and dry thermometer : 

Let x — the tension of vapour in the atmosphere, expressed in Parisian lines, to be 
found. 

e' = tension of vapour at the temperature indicated by the wet thermometer, in 
Parisian lines taken from a table. 

t — the temperature of the dry thermometer, by Reaumur's scale. 
t'= temperature of wet thermometer, by the same scale. 

b z= the height of the barometer in Parisian lines, the normal height being 336 
lines. 

Then, for temperatures above zero, Reaumur. 

x = e' — | («'— *') — 0.0011 (336—6) (t—f) 
For temperatures below zero Reaumur, 

x = e' — t (t—f) — 0.001 (336— b).(t— t') 
This, formula is very simple in its application, as will be seen by a particular example. 
Professor Erman made the following observation, May 20, 1827, 2£ A.M. 
Dry thermometer, 19°.l Reaumur. 
Wet thermometer, ll°.l " 
Difference of temperature, 8 decrees. 
The tension of vapour at ll°.l is 5.56 Parisian lines from which subtract | of the dif- 
ference of temperature, which in this case is the number 3.00. The subtraction gives 2, 
56 Parisian lines. But the barometer stood 2 lines higher than 336 ; there is therefore 
0.0022 -f- 8 = 0.02, to subtract from 2.56; which gives 2.54 Parisian lines as the tension 
of the vapour in the air at the time of observation. The above formulae are deduced from 
the expressions. 

0. 558(f— t')b 

x = e' ; and 

512— V 
558(t—t')b 



572— V 
where 512 is the latent heat of vapour at 0° Reaumur. — (Ueber die Fortschritte der Hy- 
grometrie, von Dr. E. F. August, Berlin, 1830.) 



DRYING. 



79 



Fig. 35. 



air to dry them may be greatly economized 
by a particular mode of applying it, which 
is practised in the madder-stove. The prin- 
ciple of this drying stove is illustrated by the 
annexed figure, in which a b represents a 
tight chamber, having two openings, one 
near the roof, by which hot air is admitted 
into the chamber, and another at the bottom, 
by which the air escapes into the tall chim- 
ney c. The chamber contains a series of 
stages, from the floor to the roof, on the 
lowest of which sacks, half filled with the 
damp madder roots, are first placed. In pro- 
portion as the roots dry, the bags are raised 
from stage to stage, till they arrive at the 
highest stage, where they are exposed to the 
air when hottest and most desiccating. 

As the dried roots are removed from the top, new roots are introduced below, 
and passed through in the same manner. Here the dry and hot air, after taking 
all the moisture which the roots on the highest stage will part with, descends, 
and is still capable of abstracting a second quantity of moisture from the roots 
on the next,, and so on, as it proceeds, till it passes away into the chimney ab- 
solutely saturated with moisture, after having reached the bottom of the 
chamber. 

It is frequently an object to dry a small quantity of a substance most com- 
pletely (such as an organic substance for analysis) at some steady temperature, 
such as 212°. This is effected by the following simple and elegant arrange- 
ment contrived by M. Liebig. The substance to be dried is introduced, (in 
the state of a powder if possible) into a short glass cylinder a, which may 
be three inches in length, and one and a half inch in diameter, or any other 

Fig. 36. 





convenient size, and of which the two ends are terminated by open tubes, bent 
as represented in the figure. The vessel a is immersed in a water-bath 6, which 
may be kept boiling by a lamp below. One of the tubes from a is connected 
by means of a short caoutchouc tube with the upper stopcock s, of a gas- 
holder £•, or any similar vessel, filled with water. The low opening h, of the 
gas-holder is left open, so that water can escape by it in proportion as air is 
admitted by s, which air must pass through a. The other tube from a is con- 
nected with a wide glass tube c, of eight or ten inches in length, containing 
fragments of fused chloride of calcium, in passing through which the air is de- 
prived of all moisture before it reaches the substance in a. A regulated cur- 



80 NATURE OF HE AT. 

rent of absolutely dry air at 212° may thus be conducted over the substance to 
be dried. 

NATURE OF HEAT. 

It is convenient to adopt the material theory of heat in considering its accu- 
mulation in bodies, and in expressing quantities of heat and the relative capa- 
cities of bodies for heat. Indeed every thing relating to the absorption of heat 
suggests the idea of its substantial existence; for heat, unlike light, is never 
extinguished when it falls upon a body, but is either reflected and may be 
farther traced, or is absorbed and accumulated in the body, and may again be 
derived from it without loss. But the mechanical phenomena of heat, which 
resemble those of light, may be explained with equal if not greater advantage 
by assuming an undulatory theory of heat, corresponding with the undulatory 
theory of light. A peculiar imponderable medium or ether is supposed to per- 
vade all space, through which undulations are propagated, that produce the 
impression of heat. A hot radiant body is a body possessing the faculty to 
originate or excite such undulations in the ether or medium of heat, which 
spread on all sides around it, like the waves from a pebble thrown into still 
water. Sound i3 propagated by waves in this manner, but the medium in 
which they are generally produced, or the usual vehicle of sound, is the air; 
and all the experiments on the reflection 2nd concentration of heat, by con- 
cave reflectors, may be imitated by means of sound. Thus if a watch be 
placed in the focus of one of a pair of conjugate reflecting mirrors, the waves 
of air occasioned by its beating emanate from the focus, strike against the mir- 
ror, and are reflected from it, so as to break upon the face of the opposite mir- 
ror, are concentrated into its focus, and communicate the impression of sound 
to an ear placed there to receive it. The transmission of heat from the focus 
of one mirror to the focus of the other may easily be conceived to be the pro- 
pagation of similar undulations through another and different medium from air, 
but co-existing in the same space. 

In adopting the material theory of heat, we are under the necessity of as- 
suming that there are different kinds of heat, some of which are capable of 
passing through glass, such as the heat of the sun, while others, such as that ra- 
diating from the hand, are entirely intercepted by glass. But on the undula- 
tory theory, the different properties of heat are referred to differences in the 
size of the waves, as the differences of colour are accounted for in light. 
Heat of the higher degrees of intensity, however, admits of a kind of degra- 
dation, or conversion into heat of lower intensity to which we have nothing 
parallel in the case of light. Thus when the calorific rays of the sun, which 
are of the highest intensity, pass through glass, and strike a black wall, they 
are absorbed, and appear immediately afterwards radiating from the heated wall, 
as heat of low intensity, and are no longer capable of passing through glass. 
It is as yet an insoluble problem to reverse the order of this change, and con- 
vert heat of low into heat of high intensity. We observe the same degrada- 
tion of heat, or loss of intensity, in condensing steam in distillation. The 
whole heat of the steam, both latent and sensible, is transferred without loss 
in that process, to perhaps fifteen times as much condensing water; but the in- 
tensity of the heat is reduced from 212° to perhaps 100° Fahr. The heat is 
not lost; for the fifteen parts of water at 100 are capable of melting as much 
ice as the original steam. But by no quantity of this heat atl00° can tempe- 
rature be raised above that degree: we have no means of giving it intensity. 

If heat of low is ever changed into heat of high intensity, it is in the com- 
pression of gaseous bodies by mechanical means. Let steam of half the ten- 
sion of the atmosphere, produced at 180°, in a space otherwise vacuous, be 



LIGHT. 81 

reduced into half its volume, by doubling the pressure upon it, and its tempe- 
rature will rise to 212°. If the pressure be again doubled, the temperature 
will become 250°, and the whole latent heat of the steam will now possess 
that high intensity. When air itself is rapidly compressed in a common sy- 
ringe, we have a remarkable conversion of heat of low into heat of very 
high intensity. 

It may be imagined that the elevation of temperature produced in the fric- 
tion of hard bodies has a similar origin; that it results from the conversion of 
heat of low intensity, which the bodies rubbed together possess, into heat of 
high intensity. But it would be necessary further to suppose that a supply of 
heat of low intensity to the bodies rubbed can be endlessly kept up, by con- 
duction or radiation, from contiguous bodies, as there appears to be no limit 
to the production of heat by means of friction. 

Count Rumford, by boring a cylinder of cast iron, raised the temperature of 
several pounds of cold water to the boiling point. Sir H. Davy succeeded in 
melting two pieces of ice in the vacuum of an air pump, by making them rub 
against each other, while the temperature of the air pump itself and the sur- 
rounding atmosphere was below 32°. M. Haldot observed that when the sur- 
face of the rubber was rough, only half as much heat appeared as when the 
rubber was smooth. When the pressure of the rubber was quadrupled, the 
proportion of heat evolved was increased seven fold. When the rubbing ap- 
paratus was surrounded by bad conductors of heat, or by non-conductors of 
electricity, the quantity of heat evolved was diminished.* No heat whatever 
is produced by the friction of fluids upon each other, or upon solids; nor by 
the friction of gases upon liquids or solids. 

One other point only connected with the nature of heat remains, to which 
there is at present occasion to allude — the existence of a repulsive property in 
heat. Such a repulsive power in heated bodies is inferred to exist from the ap- 
pearance of extreme mobility which many fine powders assume, such as pre- 
cipitated silica, on being heated nearly ro redness. Mr. Forbes also attributes 
to such a repulsion the vibrations which take place between metals unequally 
heated, and the production of tones, to which allusion has already been made. 
But this repulsive power was rendered conspicuous, and even measurable, by 
Mr. Powell, in the case of glass lenses, of very slight convexity, pressed together. 
On the application of heat a separation of the glasses, through extremely small 
but finite spaces, was indicated by a change in the tints which appear between 
the lenses, and which depend upon the thickness of the included plate of air. 
This repulsion between heated surfaces appears to be promoted by whatever 
tends to the more rapid communication of heat.t 



CHAPTER II. 

LIGHT. 

The mechanical properties of light constitute the science of optics, and belong, 
therefore, to physics, and not to chemistry. But it may be useful, by a short re- 
capitulation, to recall them to the memory of the reader. 

1. The rays of light emanate with so great velocity from the sun, that they 
occupy only 1\ minutes in traversing the immense space which separates the 
earth from that luminary. They travel at the rate of 192,500 miles in a second, 

* Nicholson'B Journal, XXVI. 30. t Phil. Trans. 1834, p. 485. 



82 LIGHT. 

and would, therefore, move through a space equal to the circumference of our 
globe in 1— 8th of a second. They are propagated continually in straight lines, 
and spread or diverged at the same time ; so that their density diminishes in the 
direct proportion of the square of their distance from the sun. Hence, if the 
earth were at double its present distance from the sun, it would receive only one- 
fourth of the light ; at three times its present distance, one-ninth ; at four times 
its present distance, one-sixteenth, &c. 

2. When the solar rays impinge upon a body, they are reflected from its sur- 
face, and bound off as an elastic ball, striking against the same surface in the 
same direction, would do ; or they are absorbed by the body Upon which they 
fall, and disappear, being extinguished ; or lastly, they pass through the body, 
which, in that case is transparent or diaphanous. In the first case, the body be- 
comes visible, appearing white, or of some particular colour, and we see it in the 
direction in which the rays reach the eye. In the second case, the body is in- 
visible, no light proceeding from it to the eye ; or it appears black if the sur- 
rounding objects are illuminated. In the third case, if the body be absolutely 
transparent, it is invisible ; and we see through it the object from which the light 
was last reflected. But light is often greatly affected in passing through trans- 
parent bodies. 

3. If light enters such media, of uniform density, perpendicularly to their 
surface, its direction is not altered ; but in passing obliquely out of one 
medium into another, it undergoes a change of direction. If the second 
medium be denser than the first, the ray of light is bent, or refracted, nearer 
to the perpendicular; but in passing out from a denser into a rarer medi- 
um, is refracted from the perpendicular. Thus when the ray of light r, passing 

through the air, falls obliquely upon a plate 
Fig. 37. of glass at the point a, instead of continu- 

ing to move in the same straight line, «, 6, 
it is bent towards the perpendicular at a, 
and proceeds in the direction a, c. The ray 
is bent to the side on which there is the 
greatest mass of glass. On passing out 
from the glass into the air, a rarer medium, 
at the point c, the ray has its direction 
again changed, and in this case from the 
perpendicular, but still towards the mass of glass. The amount of refraction, 
generally speaking, is proportional to the density of a body, but combustible 
bodies possess a higher refracting power than corresponds to their density. 
Hence the diamond, melted phosphorus, naphtha, and hydrogen gas, exhibit 
this effect upon light in a greater degree than other transparent bodies. Dr. 
Wollaston had recourse to this refracting power, as a test of the purity of some 
substances. Thus, genuine oil of cloves had a refracting power expressed by 
the number 1535, while that of an impure specimen was not more than 1498. 

4. In passing through many crystallized bodies, such as Iceland spar, a 
certain portion of light is refracted in the usual way, and another portion un- 
dergoes an extraordinary refraction, in a plane parallel to the diagonal which 
joins the two obtuse angles of the crystal. Such bodies are said to refract 
doubly, and exhibit a double image of any body viewed through them. 

5. Reflected and likewise doubly refracted light assume new properties. 
Common light, reflected from the surface of glass, or any bright surface 
non-metallic, is, more or less of it, converted into what is called polar- 
ized light. If it be reflected at one particular angle of incidence, 56° 45', it is 
all changed into polarized light; and the farther the angle of reflection de- 
viates from 56°, on either side, the less is polarized, and the more remains 
common light. 56° is the maximum polarizing angle for glass: 52°. 45' for 
water. The light is said to be polarized, from certain properties which it as- 




LIGHT. 



83 



sumes, which seem to indicate that the ray, like a magnetic bar, has sides in 
which reside peculiar powers. One of these new properties is, that when it 
falls upon a second glass plate, it is not reflected in the same way as common 
light. If the plane of the second reflector is perpendicular to the first, and 
the ray fall at an angle of 56°, it is not reflected at all, it vanishes; but if paral- 
lel, it is entirely reflected. Polarized light appears to possess some most ex- 
traordinary properties, in regard to vision, of useful application. It is said 
that a body which is quite transparent to the eye, and which appear upon ex- 
amination to be as homogeneous in its structure as it is in its aspect, will 
yet exhibit, under polarized light, the most exquisite organization. As an 
example of the utility of this agent in exploring mineral, vegetable and animal 
structures, Sir D. Brewster refers to the extraordinary structure of the mine- 
rals apophylite and analcime ; to the symmetrical and figurate disposition of 
siliceous crystals in the epidermis of equisetaceous plants, and to the won- 
derful variations of density in the crystalline lenses, and the integuments of 
the eyes of animals, which polarized light renders visible.* 

6. Decomposition of light. When a beam of light from the sun is admitted 

Fig. 38. 




into a dark room, by a small aperture r in a window shutter, and is intercepted 
in its passage by a wedge or solid angle of glass a b c, it is refracted as it en- 
ters, and a second time as it issues from the glass; and instead of forming a 
round spot of white light, as it would have done if allowed to proceed in its 
original direction r /, it illuminates with several colours an oblong space of 
awhile card e f, properly placed to receive it. The solid wedge of glass is 
called a prism, and the oblong coloured image on the card, the solar spectrum. 
Newton counted seven bands of different colours in the spectrum, which, as 
they succeed each other from the upper part of the spectrum represented in 
the figure, are violet, indigo, blue, green, yellow, orange and red. The beam 
of light admitted by the aperture in the window shutter, has been separated in 
passing through the prism into rays of different colours, and this separation 
obviously depends upon the rays being unequally refrangible. The blue rays 
are more considerably refracted or deflected out of their course, in passing 
through the glass, than the yellow rays, and the yellow rays than the red. 
Hence the violet end is spoken of as the most refrangible, and the red as the 
least refrangible end of the spectrum. 

The coloured bands of the spectrum differ in width, and are shaded into 
each other; and it is not to be supposed that there are really rays of seven dif- 
ferent colours. Sir D. Brewster has established, in a recent analysis of solar 
light, that there are rays of three colours only, blue, yellow, and red, which 
were well known to artists to be the three primary colours, of which all others 
are compounded. 

A certain quantity of white light, and a portion of each of the primary rays, 

* Reports of the British Association, vol. i. Report upon Optica, by Sir D. Brewster. 



84 



LIGHT. 




may be found at every point from the top to the bottom of the spectrum. But 
each of the primary rays predominates at a particular part of the spectrum. 
This point is, for the blue rays, near the top of the spectrum; for the yellow- 
rays, somewhat below the middle; and for the red rays, near the bottom of the 
Fig. 39. spectrum. Hence, there exists rays of each co- 

Blue Yellow Red * our °f every degree of refrangibility; but the 
spectrum, spectrum, spectrum, great proportion of the yellow rays is more refran- 
gible than the red, and the great proportion of the 
blue more refrangible than either the yellow or 
red. The compound spectrum which we observe, 
is in fact produced by the superposition of three 
simple spectra, a blue, a yellow, and a red spec- 
trum. The distribution of the rays in each of 
these simple spectra is represented by the shading 
in the annexed figures. Of the seven different 
coloured bands into which Newton divided the 
spectrum, not one is a pure colour. The orange 
is produced by a predominance of the yellow and 
red rays; the green, by the yellow and blue rays, 
and the indigo and violet are essentially blue, with different proportions of 
red and yellow.* 

By placing a second prism a d c, Fig. 38, in a reversed position, in contact 
with the first prism, the colours disappear, and we have a spot of white light, 
as if both prisms were absent. The three coloured rays of the spectrum, there- 
fore, produce white light by their union. 

On examining the solar spectrum, Dr. Thomas Young observed that it is 
crossed by several dark lines, that is. that there are interruptions in the spec- 
trum where there is no light of any colour. Fraunhofer subsequently found 
that the lines in the spectrum of solar light were much more numerous than 
Dr. Young had imagined, while the spectrum of artificial white flames con- 
tains all the rays which are thus wanting. One of the most notable is a double 
dark line in the yellow, which occurs in the light of the sun, moon, and pla- 
nets. In the light of the fixed stars, Syrius and Castor, the same double line 
does not occur; but one conspicuous dark line in the yellow, and two in the 
blue. The spectrum of Pollux, on the contrary, is the same as that of the 
sun. Now a very recent discovery of Sir D. Brewster has given these obser- 
vations an entirely chemical character. He has found that the white light of 
ordinary flames requires merely to be sent through a certain gaseous medium 
(nitrous acid vapour) to acquire more than a thousand dark lines in its spec- 
trum. He is hence led to infer that it is the presence of certain gases in the 
atmosphere of the sun, which occasions the observed deficiencies in the solar 
spectrum. We may thus have it yet in our power to study the nature of the 
combustion which lights up the suns of other systems. (Report upon Optics.) 
The rays of heat are distributed very unequally throughout the luminous 
spectrum; most heat being found associated with the red or least refrangible 
luminous rays, and least with the violet rays. Indeed when the solar beam is 
decomposed by a prism of highly diathermanous material, such as rock salt, 
the rays of heat are found to extend, and to have their point of maximum in- 
tensity considerably beyond the visible spectrum, on the side of the red ray. 
Hence, although there are calorific rays of all degrees of refrangibility, the 
great proportion of them are even less refrangible than the least refrangible 
luminous rays. It is observed that the least refrangible rays are absorbed in 

* Sir David Brewster, On a new analysis of the solar light, indicating three primary 
colours forming coincident spectra of equal length. — Edinburgh Phil. Trans, vol. xii. p. 123. 



CHEMICAL NOMENCLATURE AND NOTATION. 85 

greatest proportion in passing through bodies which are not highly diatherma- 
nous, such as crown-glass and water. Hence prisms of these substances, 
allowing only the more refrangible rays of heat to pass, give a spectrum which 
is hottest in the red, or perhaps even in the yellow ray, and possesses little or 
no heat beyond the border of the red ray. The inequality in refrangibility 
existing between the rays of heat and of light is decisive of the fact, that they 
are peculiar rays, that can be separated, although associated together in the 
sunbeam. Indeed, Melloni finds that light from both solar and terrestrial 
sources is divested of all heat by passing successively through water, and a 
glass, coloured green by the oxide of copper, being incapable as it issues from 
these media of affecting the most delicate thermoscope. 

The light of the sun is capable of inducing certain chemical changes which do 
not depend either upon its luminous or calorific rays, but upon the presence of 
what are called chemical rays. Thus chlorine gas, under the influence of light, 
is capable of decomposing water, combining with its hydrogen, and liberating 
oxygen ; and the chlorine in the freshly precipitated chloride of silver has a 
similar effect ; but the oxygen is the last case, instead of being set free, combines 
with the silver, and causes the colour of the compound to change from white to 
black. The moist chloride of silver is darkened more rapidly by the violet than 
by the red rays of the spectrum ; but this change is produced upon it even when 
carried a little way out of the visible spectrum on the side of the violet ray. The 
rays found in that situation are, therefore, more refrangible than any other kind of 
rays in the spectrum. Their characteristic effect is to promote those chemical 
decompositions in which oxygen is withdrawn from water and other oxides, and 
hence they are sometimes named de-oxidizing rays. These rays were like- 
wise supposed to communicate magnetism to steel needles exposed to them, but 
this opinion is no longer tenable. 



CHAPTER III 



CHEMICAL NOMENCLATURE AND NOTATION. 



There are at present fifty-five substances known, which are simple, or contain 
one kind of matter only. Their names are given in the following tables, 
together with certain useful numbers which express the quantities by weight, 
according to which the different elements combine with each other. The letter 
or symbol annexed to the name is employed to represent these particular quan- 
tities of the elements, or their combining proportions. 



86 



CHEMICAL NOMENCLATURE AND NOTATION. 



TABLE I. 



NAMES OF ELEMENTS. 



WITH THEIR SYMBOLS AND LEAST COMBINING PROPORTIONS. 



Names of Elements. 



Oxygen - 
Hydrogen 
Nitrogen 
Carbon - 
Sulphur - 
Selenium 
Phosphorus 
Boron 
Silicon - 
Chlorine 
Iodine 
Bromine . 
Fluorine 
Potassium (Kalitim) 
Sodium (Natri- 
um) 
Lithium - 
Barium - 
Strontium 
Calcium 
Magnesium 
Aluminum 
Glucinum 
Zirconium 
Thorium 
Yttrium - 
Manganese 
Iron (Ferrum) 
Zinc • • 
Cadmium 



O 
H 

N 
C 

s 

Se 

P 

B 

Si 

CI 

I 

Br 

F 

K 

Na 

L 

Ba 

Sr 

Ca 

Mg 

A\ 

G 

Zr 

Th 

Y 

Mn 

Fe 

Zn 

Cd 



Equivalents. 



100.00 

12.4795 

177.04 

76.44 

201.17 

494.58 

392.28 

136.25 

277.31 

442.65 

1579.50 

978.31 

233.80 

489.92 

290.90 
80.33 
856.88 
547.29 
256.02 
158.35 
171.17 
331.26 
420.20 
744.90 
402.51 
345.89 
239.21 
403.23 
696.77 



i Names of Eelements. 



Oas 100. H as 1. 



8.01 | Cobalt .... 

LOO I Nickel .... 
14.19 ! Copper (Cuprum) 

6.] 3 I Bismuth .... 
16.12 I Lead (Plumbum) - 
39.63 I Tin (Stannum) - 
31.44 | Cerium .... 
10.91 JLantanum . - - 
22.22 1 Uranium . - - 
35.47 1 Arsenic - - - 
126.57 1 Antimony (Stibi- - 
78.39 1 urn) 
18.74 1 Chromium . - - 
39.26 j Vanadium - - - 
I Molybdenum - - 
23.31 I Tungsten (Wol 

6.44 1 fram) 

68.66 I Columbium (Tanta. 
43.85! lum) .... 
20.521 Tellurium - - - 
12.69 j Titanium - . . 
13.72 | Osmium - . . 
26.54 | Mercury (Hydragy- 

33.67 rum) .... 
59.88 j Silver (Argentum) 
32 25 I Gold (Aurum) - 
27.72 j Platinum - . . 
27.18 Palladium - - 
32.31 I Rhodium - . - 
55.83 \ Iridium . . . 



"3 


Equivalents. 




O as 100. 


H as 1. 


Co 


368.99 


29.57 


Ni 


369.68 


29.62 


Cu 


395.70 


31.71 


Bi 


886.92 


71.07 


Pb 


1294.50 


103.73 


Sn 


735.29 


58.92 


Ce 


574.70 


46.05 


Ln 






U 


2711.36 


217.26 


As 


940.08 


75.34 


Sb 


1612.90 


129.24 


Cr 


351.82 


28.19 


V 


856.89 


68.66 


Mo 


598.52 


47.96 


W 


1183.00 


94.80 


Ta 


2307.43 


184.90 


Te 


801.76 


64.25 


Ti 


303.66 


24.33 


Os 


1244.49 


99.72 


Hg 


1265.82 


101.43 


Ag 


1351.61 


108.30 


Au 


1243.01 


99.60 


PI 


1233.50 


98.84 


Pd 


665.90 


53.36 


R 


651.39 


52.20 


lr 


1233.50 


98.84 



CHEMICAL NOMENCLATURE AND NOTATION. 



87 



TABLE II. 



NAMES OF ELEMENTS. 



ARRANGED ALPHABETICALLY WITH THEIR SYMBOLS AND LEAST COMBINING 

PROPORTIONS. 





m 


Equivalents. 


OB 


Equivalents 


Names of Elements. 


£ 1 




Names of Elements. 


c 






O as 10o|Has 1 


O asl0O.|H as 1. 


Aluminum . . - . 


Al 


171.17 


13.72 


Mercury (Hydrargy- 




i 


Antimony (Stibi- 








rum) . . . . 


Hg 


1265.82,101.43 


um) 


Sb 


1612.90 


129.24 


Molybdenum . . . . 


.Mo 


598.52 


47.96 


Arsenic 


As 


940.08 


75.34 


Nickel 


Ni 


369.68 


29.62 


Barium . . . . . 


Ba 


856.88 


68.66 


Nitrogen 


N 


177.04 


14.19 


Bismuth 


Bi 


886.92 


71.07 


Osmium 


Os 


1244.49 


99.72 


Boron - - - . . 


B 


136.25 


10.91 


Oxygen 


O 


100.00 


fc.01 


Bromine - - - . - 


Br 


978.31 


78.39 


Palladium 


Pd 


665.90 


53.36 


Cadmium 


Cd 


696.77 


55.83 


Phosphorus . . . . 


P 


392 28 


31.44 


Calcium - - - . . 


Ca 


256.02 


20.52 


Platinum 


PI 


1233.50 


98.84 


Carbon 


C 


76.44 


6.13 


Potassium (Kalium . . 


K 


489.92 


39.26 


Cerium - . . . . 


Ce 


574.70 


46.05 


Rhodium 


R 


651.39 


52.20 


Chlorine 


CI 


442.65 


35.47 


Selenium 


Se 


494.58 


39.63 


Chromium 


Cr 


351.82 


28.19 


Silicon 


Si 


277.31 


22.22 


Cobalt 


Co 


368.99 


29.57 


Silver (Argentum) . . 


A? 


1351.61 


108.30 


Columbium (Tanta- 








Sodium (Natri- 








lum) 


Ta 


2307.43 


184.90 


um) 


Na 


290.90 


23.31 


Copper (Cuprum) - - 


Cu 


395.70 


31.71 


Strontium . 


Sr 


547.29 


43.85 


Fluorine 


F 


233.80 


18.74 


Sulphur . 


S 


201.17 


16.12 


Glucinum 


G 


331.26 


26.54 


Tellurium 


Te 


801.76 


64.25 


Gold (Aurum) - - - 


Au 


1243.01 


99.60 


Thorium . . 


Th 


744.90 


59.88 


Hydrogen 


l H 


12 4795 


1.00 


Tin (Stannum) . . . 


Sn 


735.29 


58.92 


Iodine 


1 


1579.50 


126.57 


Titanium 


Ti 


303.66 


24.33 


Iridium 


Ir 


1233 50 


98.84 


Tungsten (Wolfram) 


W 


1183.00 


94.80 


Iron (Ferrum) - - - 


Fe 


339.21 


27.18 


Vanadium 


V 


856.89 


68.66 


Lead (Plumbum) - - 


Pb 


1294.50 


103.73 


Uranium 


U 


2711.36 


217.26 


Lithium 


L 


80.33 


6.44 


Yttrium 


Y 


402.51 


32.25 


Lantanum 


Ln 






Zinc 


Zn 


403.23 


32.31 


Magnesium - - - - 


Mg 


158.35 


1269 


Zirconium 


Zr 


420.20 


33.67 


Manganese . . . . 


Mn 


345.89 


27.72 











88 



CHEMICAL NOMENCLATURE AND NOTATION 



TABLE III. 



ALPHABETICAL ARRANGEMENT OF SYMBOLS. 



o as 100. 


H asl. 


O as 100. 


H as 1. 


Ag indicates 


1351.61 


108.30 Silver (Argen. 


N 


indicates 177.04 


14.19 Nitrogen 






turn) 


Na 


290.90 


23.31 Sodium (Na- 


Al 


171.17 


13.72 Aluminum 






trium) 


As 


940.08 


75.34 Arsenic 


Ni 


369.68 


29.62 Nickel 


Au 


1243.01 


99.60 Gold (Aurum) 


O 


100.00 


8.01 Oxygen 


B 


136.25 


10.91 Boron 


Os 


1244.49 


99.72 Osmium 


Ba 


856.88 


68.66 Barium 


P 


392.28 


31.44 Phosphorus 


Bi 


886.92 


71.07 Bismuth 


Pb 


1294.50 


103.73 Lead (Plum- 


Br 


978.31 


78.39 Bromine 






bum) 


c 


76.44 


6.13 Carbon 


Pd 


665.90 


53.36 Palladium 


Ca 


256.02 


20.52 Calcium 


PI 


1233.50 


98.84 Platinum 


Cd 


69677 


55.83 Cadmium 


R 


651.39 


52.20 Rhodium 


Ce 


574.70 


46.95 Cerium 


S 


201.17 


16.12 Sulphur 


CI 


442.65 


35.47 Chlorine 


Sb 


1612.90 


129.24 Antimony 


Co 


368.90 


29.57 Cobalt 






(Stibium) 


Cr 


351.82 


28.19 Chromium 


Se 


494.58 


39.63 Selenium 


Cu 


395.70 


31.71 Copper (Cu- 


Si 


277.31 


22.22 Silicon 






prum) 


Sn 


735.29 


58.92 Tin (Stan- 


F 


233.80 


18.74 Fluorine 






num) 


Fe 


339.21 


27.18 Iron (Ferrum) 


Sr 


547.29 


43.85 Strontium 


G 


331.26 


2654 Glucinum 


Ta 


2307.43 


184-90 Columbium 


H 


12.4795 


1.00 Hydrogen 






(Tantalum) 


Hg „ 


1265.82 


101.43 Mercury (Hy- 


Te 


801.76 


64.25 Tellurium 






drargyrum) 


Th 


744.90 


59.88 Thorium 


I 


1579.50 


126.57 Iodine 


Ti 


303.66 


24.33 Titanium 


Ir 


1233.50 


98.84 Iridium 


U 


2711.36 


217.26 Uranium 


K 


489.92 


39.26 Potassium 


V 


856.89 


68.66 Vanadium 






(Kalium) 


w 


1183.00 


94.80 Tungsten 


L 


80.33 


6.44 Lithium 






(Wolfram) 


Ln „ 




Lantanum 


Y 


402.51 


32.25 Yttrium 


Mg „ 


158.35 


12.69 Magnesium 


Zn 


403.23 


32.31 Zinc 


Mn 


345.89 


27.72 Manganese 


Zr 


420.20 


33.67 Zirconium 


Mo 


598.52 


47.96 Molybdenum 









CHEMICAL NOMENCLATURE AND NOTATION. 89 

In the class of simple substances are placed all those bodies which are not 
known to be compound, on the principle that whatever cannot be decomposed 
or resolved by any process of chemistry into other kinds of matter, is to be con- 
sidered as simple. They are the only bodies the names of which are at present 
independent of any rule. An attempt was, indeed, made on the first introduc- 
tion of a systematic nomenclature, to make the names of several of them signi- 
ficant ; but some confusion in regard to their derivatives was found to be the 
consequence of this, and many of them being familiar substances, were almost 
of necessity allowed to retain the names they bear in common language ; such 
as, sulphur, tin, silver, and the other metals known in the arts. To newly dis- 
covered elements, however, such names were applied as were suggested by any 
striking physical property they possessed, or remarkable circumstance in their 
history. The names of the newer metals, platinum, potassium, vanadium, etc., 
have a common termination, which serves to distinguish them as metals. Other 
classes of elementary bodies, resembling each other in certain particulars, are 
marked in a similar manner; such as the class comprising carbon, boron and 
silicon, and that composed of chlorine, iodine, bromine, and fluorine. 

The names of compound bodies are contrived to express their composition, 
and the class to which they belong, and are founded on a distribution of com- 
pounds into three orders, namely: first, compounds of one element with another 
element, as for instance, oxygen with sulphur in sulphuric acid, or oxygen with 
sodium in soda, which are called binary compounds. Secondly, combinations 
of binary compounds with each other, as of sulphuric acid with soda in Glauber's 
salt, and the salts generally, which are termed ternary compounds. And thirdly, 
combinations of salts with one another, or double salts such as alum, which are 
quaternary compounds. 

1. — Of the compounds of the first order, the greater number known to the 
original framers of the chemical nomenclature, contained oxygen as one of their 
two constituents ; and hence, an exclusive importance was attached to that ele- 
ment. .Its compounds with the other elementary bodies, may be divided from 
their properties into: (a) the class of neutral bodies and bases; and (6) the class 
of acids. 

(a) To members of the first class, the generic term oxide was applied, the first 
syllable of oxygen, with a termination indicative of combination ; to which the 
name of the other element was joined to express the specific compound. Thus 
a compound of oxygen and hydrogen is oxide of hydrogen; of oxygen and po- 
tassium, oxide of potassium; of which compounds the first or water, is an in- 
stance of a neutral oxide ; and the second or potash, of a base or alkaline oxide. 
But the same elementary body often combines with oxygen in more than one 
proportion, forming two or more oxides; to distinguish which, the Greek prefix 
proto (Trpzrrog first) is applied to the oxide containing the least proportion of oxy- 
gen ; deuto(hvref>os, second) to the oxide containing more oxygen than the pro- 
toxide; and trito (rptror, third) to the oxide containing still more oxygen than 
the deutoxide ; which last oxide if it contains the largest proportion of oxygen, 
with which the element can unite to form an oxide, is more commonly named 
the peroxide, from per the Latin particle of intensity. Thus the three compounds 
of the metal manganese and oxygen are distinguished as follows: 

Composition 

Names Manganese Oxygen 

Protoxide of manganese. . . 100 28.91 

Deutoxide of manganese. . . 100 43.36 

Peroxide of manganese. . . 100 57.82 

As the prefix per implies simply the highest degree of oxidation, it may be 

applied to the second oxide where there are only two, as in the oxides of iron, 

the second oxide of which is called, indifferently, the deutoxide or peroxide of 

8* 



90 CHEMICAL NOMENCLATURE AND NOTATION. 

iron. M. Thenard, in the last edition of his Traite de Chimie, avoids the use of 
the term deutoxide, and confines the application of peroxide to such of these ox- 
ides as, like the peroxide of manganese, do not combine with acids. He applies 
the names sesquioxide and binoxide to oxides, which are capable of combining 
with acids, and contain respectively, once and a half and twice as much oxygen 
as the protoxides of the same metal. He has thus the protoxide, sesquioxide and 
peroxide of manganese, the protoxide and sesquioxide of iron, the protoxide and 
binoxide of tin, etc. The sesquioxides of iron and manganese of Thenard, are 
also named tritoxides by some French chemists, as to double the proportion of 
metal in the protoxides, they possess three times as much oxygen. Certain in- 
ferior oxides, which do not combine with acids are called suboxides; such as 
suboxide of lead, which contains less oxygen than the oxide distinguished as the 
protoxide of the same metal. 

The compounds of chlorine and certain other elements are distinguished in 
the same manner as the oxides. Such elements resemble oxygen in several re- 
spects, particularly in the manner in which their compounds are decomposed by 
electricity. Chlorine, for example, like oxygen, proceeds to the positive pole, 
and is therefore classed with oxygen as an electro-negative substance, in a di- 
vision of elements grounded on their electrical relations. Thus with the other 
elementary bodies, 

Oxygen forms oxides, 

Chlorine „ chlorides, 

Bromine „ bromides, 

Iodine „ iodides, 

Fluorine „ fluorides, 

Cyanogen „ cyanides, 

Sulphur „ sulphurets. 
As cyanogen, although a compound body, comports itself in its combinations 
like an electro-negative element, its compounds are named in the same manner 
as the oxides. When several chlorides of the same metal exist, they are dis- 
tinguished by the same numerical prefixes as the oxides. Thus we have the 
protochloride and the deutochloride or perchloride of iron ; the protochloride, 
and the bichloride of tin ; the application of the prefix bi being more generally 
sanctioned in the case of chlorides than oxides. The compounds of sulphur 
greatly resemble the oxides, but they are named sulphurets and not sulphides. 
Berzelius indeed applies the term sulphuret to such binary compounds of sulphur 
only as are basic or correspond with basic oxides ; while sulphide is applied to 
such as are acid, or correspond with acid oxides. Hence, he has the sulphurpt 
of potassium, and the sulphide of arsenic and sulphide of carbon. Compounds 
of chlorine are distinguished by him into chlorurets and chlorides, on the same 
principle ; thus he speaks of the chloruret of potassium and of the chloride of 
posphorus. But these distinctions have not been regarded by French or En- 
glish chemists. 

Compounds of carbon and phosphorus with electro-positive elements are named 
carburets and phosphurets, as the carburet of iron, the phosphuret of lead. In all 
such cases it is the name of the electro-negative element, or that which most re- 
sembles oxygen, which is placed first in the name of the compound, and has a 
termination expressive of combination attached to it. Thus a compound of 
chlorine and phosphorus is called chloride of phosphorus, and not phosphuret of 
chlorine : of sulphur and carbon, sulphuret of carbon, and not carburet of sul- 
phur. The combinations of metallic elements among themselves are distinguished 
by the general term alloys, and those of mercury as amalgams. 

(b) The binary compounds of oxygen which possess acid properties are named 
on a different principle. Thus the acid compound of titanium and oxygen is 
called titanic acid ; of chromium and oxygen, chromic acid ; or the name of 



CHEMICAL NOMENCLATURE AND NOTATION. 91 

the acid is derived from that of the substance in combination with oxygen, 
with the termination ic. Where the same element was known to form two acid 
compounds with oxygen, the termination ous was applied to that which con- 
tained the least proportion of oxygen, as in sulphurous and sulphuric acids. On 
the discovery of an acid compound of sulphur which contained less oxygen than 
that already named sulphurous acid, it was called hypo sulphurous arid, (from 
the Greek Cno, under) and another new compound, intermediate between the 
sulphurous and sulphuric acids was named hypo sulphuric acid. On the same 
principle, an acid containing a greater proportion of oxygen than that already 
named chloric acid was named hyperchloric acid, (from the Greek iirep, over). 
The names of the different acid compounds of oxygen and sulphur, which have 
been referred to for illustration, with the relative proportions of oxygen which 
they contain, are as follows ; 



Names. 


Corr 
Sulphur. 


iposi 


tion 

Ox v ere n. 


Hyposulphurous acid 


100 




49.75 


Sulphurous acid 


100 




99.50 


Hyposulphuric acid 


100 




124.37 


Sulphuric acid 


100 




149.25 



This system has been adopted for all analogous acids. An acid of chlorine, 
containing more oxygen than chloric acid, is named hyperchloric acid, and other 
similar compounds, which all contain an unusually large proportion of oxygen 
are distinguished in the same manner, as hyperiodic acid and hypermanganic 
acid. The hyperchloric acid is also sometimes called perchloric and oxichloric ; 
but these last terms do not seem so suitable as the first. 

Another class of acids exists in which sulphur is united with the other ele- 
ment in the place of oxygen. The acids thus formed are called sulphur-acids. 
The names of the corresponding oxygen acids are sometimes applied to these, 
with the prefix sulpho, as sulpho-arsenious and sulpho-arsenic acids, which 
resemble arsenious and arsenic acids respectively in composition, but contain 
sulphur instead of oxygen. Lastly, certain substances, such as chlorine, sul- 
phur and cyanogen, form acids with hydrogen, which are called hydrogen 
acids, or hydr acids. In these acid compounds the names of both constituents 
appear as in the terms hydrochloric ucid, hydrosulphuric add, and hydro- 
cyanic acid. Thenard has lately altered these names to chlorhydric, sulpho- 
hydric and cyanhydric acids, which are certainly preferable terms. 

2. — Compounds of the second order, or salts, are named according to the 
acid they contain, the termination ic of the acid being changed into ate, and ous 
into ite. Thus a salt of sulphuric acid is a sulphate: of sulphurous acid, a sul- 
phite; of hyposulphurous acid, a hyposulphite; of hyposulphuric acid, a hypo- 
sulphate; and of hyperchloric acid, a hyperchlorate; and the name of the oxide 
indicates the species, as the sulphate of the oxide of silver, or the sulphate of 
silver, for the oxide of the metal being always understood it is unnecessary to 
express it, unless when more than one oxide of the same metal combines with 
acids, as sulphate of the protoxide of iron, and sulphate of the peroxide of 
iron. These salts are sometimes called protosulphate and persulphate of iron, 
where the prefixes proto and per refer to the degree of oxidation of the iron. 
The two oxides of iron are named ferrous oxide and ferric oxide by Berzelius, 
and the salts referred to, the ferrous sulphate, and the ferric sulphate. The 
names stannous sulphate and stannic sulphate express in the same way, the 
sulphate of the protoxide of tin, and the sulphate of the peroxide of tin. But 
such names, although truly systematic and replacing very cumbrous expres- 
sions, involve too great a change in chemical nomenclature to be speedily 
adopted. Having found its way into common language, chemical nomencla- 
ture can no longer be altered materially without great inconvenience. It must 



92 CHEMICAL NOMENCLATURE AND NOTATION. 

be learned as a language, and not be viewed and treated as the expression of a 
system. A swper-sulphate contains a greater proportion of acid than the sul- 
phate or neutral sulphate; a fo'-sulphate twice as much, and a ses^i/i-sulphate 
once and a half as much as the neutral sulphate; while a sw6-sulphate con- 
tains a less proportion than the neutral salt; the prefixes referring in all cases 
to the proportion of acid in the salt, or to the electro-negative ingredient, as in 
the case of oxides. The excess of base in sub-salts is sometimes indicated by 
Greek prefixes expressive of quantity, as r/i-chromate of lead, /m-acetate of 
lead, but this deviation from rule is apt to lead to confusion. If a precise ex- 
pression for such subsalts were required, it would be better to say the bibasic 
subchromate of lead, the tribasic subacetate of lead. But the names of both 
acid and basic salts are less in accordance with correct views of their consti- 
tution, than the names of any other class of compounds. 

Combinations of water with other oxides are called hydrates, as hydrate of 
potash, hydrate of boracic acid. 

3. — In the names of quaternary compounds or of double salts, the names of 
the constituent salts are expressed, thus: sulphate of alumina and potash is 
the compound of the sulphate of alumina with the sulphate of potash; tartrate 
of potash and soda, the compound of the tartrate of potash with the tartrate of 
soda; the name of the acid being expressed only once, as it is the same in both 
of the constituent salts. The names alum and Rochelle salt which have been 
assigned by common usage to the same double salts, are likewise received in 
scientific language. The chloride of platinum and potassium expresses, in 
the same way a compound of chloride of platinum with chloride of potassium. 
An oxichloride, such as the oxichloride of mercury, is a compound of the 
oxide with the chloride of the same metal. 

The present nomenclature does not furnish precise expressions for many 
new classes of compounds, the existence of which was not contemplated by its 
inventors, and many of its names express theoretical views of the constitution 
of bodies which are doubtful, and not admitted by all chemists. But its defi- 
ciencies are supplied, and the composition of bodies more accurately repre- 
sented, in certain written expressions, or chemical formulae, which are also 
employed to denote particular substances, and which form a valuable supple- 
ment to the nomenclature still generally used. These formulas are constructed 
on the simplest principles, and besides supplying the deficiencies of the old 
nomenclature, they at once exhibit to the eye the composition of bodies, and 
afford a mechanical aid in observing relations in composition, of the same kind 
as the use of figures in the comparison of arithmetical sums. 

Symbols of the elements. Each elementary substance is represented by the 
initial letter of its Latin name as will be seen by reference to Table I, page 
86; but when the names of two or more elements begin with the same letter, 
a second in a smaller .character is added for distinction; thus oxygen is repre- 
sented by the letter 0, the metal osmium by Os, fluorine by F, and iron (fer- 
rum) by Fe; small letters, it is to be observed, never being significant of 
themselves, but employed only in connexion with the large letters as distinc- 
tive adjuncts. These symbols represent, at the same time, certain relative 
quantities of the elements, the letter expressing not oxygen indefinitely, but 
100 parts by weight of oxygen, and Fe, 339 parts by weight of iron, or any 
other quantities of these two substances which are in the proportion of these 
numbers; 8 parts of oxygen, for instance, and 27.18 of iron. It will imme- 
diately be explained that the elementary bodies combine with each other in 
certain proportional quantities only, which may be expressed by one or other 
of the two series of numbers placed against the names of the elements in the 
tables (pages 86, 87, 88.) These quantities are conveniently spoken of, as the 
equivalent quantities, or equivalents, combining proportions ox proportions of 



CHEMICAL NOMENCLATURE AND NOTATION. 93 

the elements. The symbol or letter, of itself representing one equivalent of 
the element, several equivalents are represented by repeating the symbol, or 
by placing figures before it, thus Fe Fe, or 2 Fe, and 3 O, which mean two 
equivalents of iron and three of oxygen; or small figures are placed either above 
or below the symbol', and to the right, thus Fe 2 , O 3 , or Fe 3 , 3 , which ex- 
pressions are of the same value as the former, but are used only when sym- 
bols are placed together in the formulae of compounds. Two equivalents of 
an element are often expressed by placing a dash through, or under its sym- 
bol, as 2C, by £ or C, but such abbreviations will not be made use of in the 
present work. The substance represented by any symbol, which occurs to 
the reader in the following pages, may be learned by reference to the alpha- 
betical arrangement of symbols, page 88. 

Formulae, of Compounds. The collocation of symbols expresses combina- 
tion; thus FeO represents a compound of one equivalent or proportion of iron, 
and one of oxygen, or the protoxide of iron; S0 3 , a compound of one equiva- 
lent of sulphur, and three of oxygen, that is one equivalent of sulphuric acid: 
and sulphate of iron itself consisting of one equivalent of each of the preceding 
compounds, may be represented as follows: 

FeO S0 3 , or 
FeO + S0 3 , or 
FeO, S0 3 , 
The sign plus (-f ) or the comma, being introduced in the second and third 
formulae, to indicate a distribution of the elements of the salt into its two proxi- 
mate constituents, oxide of iron, and sulphuric acid, which is not so distinctly 
indicated in the first formula. It may often be advantageous to make use of 
both the comma and the plus sign in the same formula, and then it would be 
a beneficial practice to use them as in the following formula for the double 
sulphate of iron and potash: 

FeO, S0 3 -fKO, S0 3 
in which the comma is employed to indicate combination more intimate in de- 
gree, or of a higher order than the plus sign, namely, of the oxide with the 
acid in each salt, while the combination of the two salts themselves is ex- 
pressed by the sign -f • 

The small figures in the preceding formulae affect only the symbol or letter 
to which they are immediately attached. Larger figures placed before and in 
the same line with the symbols apply to the compound expressed by the sym- 
bols. Thus 3S0 3 , means three equivalents of sulphuric acid; 2PbO, two 
equivalents of oxide of lead. But the interposition of a comma or plus sign 
prevents the influence of the figure extending farther, thus 

2Pb 0, CrO,, or 
2PbO-fCr0 3 , 
is two proportions of oxide of lead, and one of chromic acid, or the subchro- 
mate of lead. To make the figure apply to symbols separated by the comma 
or plus sign, it is necessary to enclose all that is to be affected within brackets, 
and place the figure before them. Thus, 

2 (PbO, Cr0 3 ) 
means two proportions of the chromate of lead. The following formulae of 
two double salts with their water of crystallization, exhibit the application of 
these rules: \ 

Iron-alum, or the sulphate of peroxide of iron and potash, 

KO, S0 3 + Fe 2 3 3S0 3 -+24H0 
Oxalate of peroxide of iron and potash, 

3 (KO, C 3 3 ) + Fe 2 3 , 3C 2 3 + 6H0. 
It will be found to conduce to perspicuity, to avoid either connecting two for- 
mulae of different substances not in combination, by the sign plus, or allowing 



94 CHEMICAL NOMENCLATURE AND NOTATION. 

them to be separated merely by a comma, as the plus and comma between sym- 
bols or formulae are conventionally understood to unite the formulae into one, 
and to express combination; and indeed it is advisable to write every com- 
plete formula apart, and in a line by itself, if possible. 

The only other circumstance to be attended to in the construction of such 
formula? is the arrangement of the symbols or letters, which is not arbitrary. 
In naming a binary compound, such as oxide of iron, chloride of potassium, 
etc., we announce first the oxygen or element most resembling it in the com- 
pound, and which is called the electro-negative ingredient, but in the formu- 
lae of the same bodies, it is the other, or the electro-positive element which is 
placed first, as in FeO, and KC1. In the formulae of salts, it is likewise the 
electro-positive constituent or the basic oxide which is placed first, and not 
the acid. Thus the sulphate of potash is KO, S0 3 , and not S0 3 , KO. 
Information respecting the constitution of a compound may often be expressed 
in its formula, by attending to this rule. Thus sulphuric acid of specific gra- 
vity 1.780, contains two proportions of water to one of acid, but by giving to 
it the following formula, 

HO,S0 3 +HO, 
we express that one proportion only of water is combined as a base with the 
acid, and that the second proportion of water, the formula of which follows 
that of the acid, is in combination with this sulphate of water. 

The above system of notation is complete, and sufficiently convenient for 
representing all binary compounds, and compounds belonging to the organic 
department of the science, in the formulae of which the ultimate elements only 
are expressed. But when salts and double salts are expressed, the formulae 
often become inconveniently long. They may often be greatly abbreviated, 
and made more distinct by expressing each equivalent of oxygen in an oxide 
or acid by a dot placed over the symbol of the other element, thus, 
Protoxide of iron, Fe. 
Sulphuric acid, S*. 

Crystallized sulphate of protoxide of iron, FeS,H-J~6H. 
Alum, KS,AlAlS3-f24H 

Felspar, KSU'lAl §i s 

Oxalate of peroxide of iron and potash, 3KCC-fFeFe, 3CC -f 6H. Such 
formulae are more compact, and more easily compared with each other, the 
relation between the mineral felspar and alum without its water of crys- 
tallization, being seen at a glance on thus placing their formulae together, 
the one having the symbol for silicon, the other that for sulphur, but every 
thing else remaining the same. This abbreviated plan also exhibits more dis- 
tinctly the relation between the equivalents of oxygen in the different consti- 
tuents of a salt, which is always important. 

It is to be observed, that the oxygen expressed by the dots placed over a 
letter is brought under the influence of the small figure attached to that letter, as 
for example, g' in the preceding formula of alum, means three proportions 
of sulphuric acid, so that this sign has the same value as if it were writ- 
ten 3S. 

Equivalents of sulphur are likewise sometimes expressed by commas placed 

over other symbols, as the trito-sulphuret of arsenic by As, but such com- 
pounds are not of constant occurrence like the oxides, and do not create the 
same necessity for any new and arbitrary symbol. A compound body, such 



COMBINING PROPORTIONS. 



95 



as cyanogen, which combines with a numerous series of other bodies is often 
for brevity expressed by the initial letter of its name, as 

Cyanogen . Cy, 

Benozoyle . Bz; 

and the organic acids are sometimes expressed by a letter in the same way, 
but with the minus sign ( — -) placed over it, thus, 

Acetic acid, by A 
Tartaric acid, by T" 
But the arbitrary characters of this kind will always be explained, on the oc- 
casion of their introduction. 



COMBINING PROPORTIONS. 

All analyses prove that the composition of the bodies is fixed and invariable: 
100 parts of water are uniformly composed of 11.1 parts by weight of hydro- 
gen, and 88.9 parts of oxygen, its constituents never varying either in nature 
or proportion. This and other substances may exist in an impure condition, 
from an admixture of foreign matter, but their own composition remains the 
same in all circumstances. It is this constancy in the composition of bodies 
which gives to chemical analyses all their value, and rewards the vast care 
necessarily bestowed upon their execution. 

An examination of the composition of any class of bodies containing an ele- 
ment in common, such as the oxides, shows that any one element unites with 
very different quantities of the other elements. Thus in each of the five 
oxides, of which the composition is given below, the oxygen and other con- 
stituent appear in a different relation to each other. 



Composition of Oxides. 



Water. 


Oxide of Copper. 


Oxide of Zinc. 


Oxide of Lead. Oxide of Silver. 


Oxygen 88.9 

Hydrogen 11. L 

100 


Oxvgen 20.2 

Copper 79.8 

100 


Oxygen 19.1 

Zinc 80.9 

100 


Oxygen 7.2 Oxvgen 6.9 

Lead 92.8 Silver 93.1 

100 1 100 



But the relation between the oxygen and the other constituent in these oxides 
will be seen more distinctly by stating their composition in such a way as to 
have the oxygen expressed by the same number in every case, or made equal 
to 100 parts. Thus, 



Water. 


Oxide of Copper. 


Oxide of Zinc. 


Oxide of Lead. 


Oxide of Silver. 


Oxygen 100 

Hydrogen.... 12 5 

112.5 


Oxygen 100 

Copper 396 

496 


Oxygen 100 

Zinc 403. 

503 


Oxygen 100 

Lead 1294 

1394 


Oxygen 100 

Silver 1352 

1452 



From which it follows, that 

12.5 parts of hydrogen, 
396 parts of copper, 
403 parts of zinc, 
1294 parts of lead, 
1352 parts of silver, 
combine with 1 00 parts of oxygen. 



96 COMBINING PROPORTIONS. 

These numbers prove to* be in some degree characteristic of the sub- 
stances to which they are here attached, for when the composition of the sul~ 
phurets of the same substances is examined, it is found, that exactly corre- 
sponding quantities of hydrogen, copper, &c, likewise combine with one and 
the same quantity of sulphur, although not with 100 parts of that element 
as of oxygen. The conclusion from an examination of the sulphurets is, that 
12.5 parts of hydrogen, 
396 parts of copper, 
403 parts of zinc, 
1294 parts of lead, 
1352 parts of silver, 
combine with 201 parts of sulphur. An examination of the chlorides of the 
same five elements likewise proves, that 
12.5 parts of hydrogen, 
396 parts of copper, 
403 parts of zinc, 
1294 parts of lead, 
1352 parts of silver, 
combine with 442 parts of chlorine. Hydrogen, copper, &c, are indeed 
found to unite in the proportions repeated in these tables with a certain or 
constant quantity of all other elements, as for example with 978 bromine, with 
1579 iodine, etc. 

On extending the inquiry to other substances, it appears that for each of 
them a number may be found which expresses in like manner, the proportion 
in which that substance unites with 100 parts of oxygen, 201 of sulphur, 442 
of chlorine, &c. These numbers constitute the combining proportions, or 
equivalent quantities of bodies, which are introduced in the tables of the names 
of the elements at the beginning of this chapter, and which are the quantities 
understood to be expressed by the chemical symbols of these bodies. Any 
series of numbers may be chosen for the combining proportions, provided the 
true relation between them is preserved, as in the second series of numbers 
given in the same tables, which are all 12£ times less than the numbers of the 
first series. The second series expresses particularly the proportional quan- 
tity of each of the elements, which unites with one part of hydrogen, the ele- 
ment, the combining proportion of which is the smallest, and is on that account 
taken here as unity. But the other series which is the most convenient, being 
adopted, it may then be stated in general terms that the combining proportion 
of a simple substance represents the quantity of that substance which combines 
with 100 parts of oxygen to form a protoxide. 

The first law of combination is, that bodies unite with each other in their com- 
bining proportions only, or in multiples of them, and in no intermediate propor- 
tions. This law may be illustrated by the compounds of nitrogen and oxygen, 
which are five in number, and are composed as follows : 

Protoxide of nitrogen . . . Nitrogen 177, oxygen 100 



Deutoxide of nitrogen 
Nitrous acid 
Peroxide of nitrogen 
Nitric acid 



Nitrogen 177, oxygen 200 
Nitrogen 177, oxygen 300 
Nitrogen 177, oxygen 400 
Nitrogen 177, oxygen 500 



The first compound consists of a single combining proportion of each of its con- 
stituents. But in the other compounds a single proportion of nitrogen is united 
with quantities of oxygen which correspond exactly with two, three, four and 
five combining proportions of that element. In the greater number of binary 
compounds, one of the constituents at least is present in the proportion of a sin- 
gle equivalent, like the nitrogen in this series, while the other constituent, gene- 



COMBINING PROPORTIONS. 97 

rally the oxygen in oxides, and the electro-negative element in other compounds, 
is present in a multiple of its combining proportion. But the number of com- 
bining proportions which may enter into a compound, is subject to considerable 
variation as will appear from the following examples. 



One proportion oxygen -f~ 


One proportion 


hydrogen, 


forms 


water. 


Two proportions oxygen -f- 


One „ 


hydrogen, 


forms 


peroxide of hydrogen. 


One proportion oxygen 4" 


Two proportions 


copper, 


forms 


suboxide of copper. 


One „ sulphur -j- 


Three „ 


oxygen, 


ii 


sulphuric acid. 


Two proportions sulphur -f- 


Two „ 


oxygen, 


form 


hyposulphurous acid. 


Two „ iron -f- 


Three „ 


oxygen, 


it 


peroxide of iron. 


Two „ sulphur -j- 


Five 


oxygen, 


ii 


hyposulphuric acid. 


Tvvo „ manganese -j- 


Seven „ 


oxygen, 


» 


hypermanganic acid. 



Representing the constituents of a binary compound by A and B, the last being 
the oxygen or electro-negative constituent, the most frequent combination is 
A-l-B, then A+2B, A+3B, and A+5B. The combination of 2A-f 3B, is not 
unfrequent, but 2 A -f B, A + 4B, A-f 7B, 2 A -f 2B, or 2 A -f 5B are of comparative- 
ly rare occurrence. Combination between two elements is not known to occur 
in more complicated ratios than the preceding, if the compounds of carbon and 
hydrogen be excepted, which are numerous and exhibit great diversity of com- 
position, like the compounds of organic chemistry generally, to which they pro- 
perly belong. 

Combination likewise takes place among bodies which are themselves com- 
pound, in proportional quantities, which are fixed, and determined by the law, 
that the combining number of a compound body is always the sum of the com- 
bining numbers of its constituents. Thus oil of vitriol, which is a combination 
of water and sulphuric acid, is composed of these bodies in the proportion of 

Water 112.5 

Sulphuric acid 501 

in which the combining proportion of the water (112.5) is the sum of the pro- 
portions of its constituents; namely, of oxygen 100 and of hydrogen 12.5; and 
that of sulphuric acid (501,) of those of sulphuric 201 and of oxygen 300, there 
being three proportions of oxygen in sulphuric acid. The combining proportion 
of oxide of zinc is 503, the sum of oxygen 100 and zinc 403, and the compound 
of this oxide with sulphuric acid, or the salt, sulphate of zinc, consists of 

Oxide of zinc 503 

Sulphuric acid 501 



1004 
Of potash, the combining proportion is 590, or oxygen 100 added to potassium 
490, and to this proportion of potash the usual proportion of sulphuric acid is 
attached in the sulphate of potash, which is composed of 

Potash 590 

Sulphuric acid 50 i 



1091 
Of these salts themselves, the combining proportions ought to be the sums ob- 
tained by the addition of the numbers of their constituents; and accordingly the 
double sulphate of zinc and potash consists of 

Sulphate of zinc . . . . . 1004 
Sulphate of potash . . . . 1091 



2095 
Of nitric acid the constituents are one proportion of nitrogen 177, and five of 
oxygen 500, making together 677, which is the combining proportion of that acid, 
and is found to unite with 1 12.5 water, with 503 oxide of zinc, and with 590 
9 



98 COMBINING PROPORTIONS. 

potash, or with the same quantities of these oxides as combine with 501 sulphu- 
ric acid. Carbonic acid is composed of one proportion of carbon 76, and two 
proportions of oxygen 200, so that its combining number is 276, in which pro- 
portion it unites with 590 potash, to form the carbonate of potash. The equiva- 
lent quantities of all other acids and bases correspond in like manner with the 
numbers deducible from their composition. Indeed the law is found to hold in 
compounds of every class and character, and whether they contain few or many 
equivalents of their elements. Thus of the vegeto-alkali morphia, which con- 
tains a large number of equivalents, the combining proportion is the high num- 
ber 3687, which is the sum of thirty-five proportions of carbon 2660, twenty 
proportions of hydrogen 250, one proportion of nitrogen 177, and six proportions 
of oxygen 600; 3687 morphia being found to unite with 501 sulphuric acid, or 
a combining proportion of that acid, to form the sulphate of morphia. 

Compound bodies likewise unite among themselves in multiples of their com- 
bining proportions, as well as in single equivalents. Thus 590 potash combine 
with 652 chromic acid, and with double that quantity, or 1 304 chromic acid to form 
the yellow and the red chromates of potash; the first containing one equivalent, and 
the second two equivalents of acids. The occurrence of multiple proportions 
was well illustrated by Dr. Wollaston in the carbonate and bicarbonate of pot- 
ash. A quantity of the latter salt being divided into equal parts, one half was 
exposed to a red heat, by the effect of which the salt lost some carbonic acid and 
became neutral carbonate, and both portions being afterwards decomposed by 
an acid, the salt in its original condition was found to afford a measure of car- 
bonic acid gas exactly the double of that yielded by the portion exposed to the 
high temperature. By experiments equally simple and convincing, he proved 
that in the three salts formed by oxalic acid and potash, the quantities of acid 
which combine with the same quantity of alkali are rigorously among them- 
selves as the numbers 1, 2, and 4. The composition of all other super and sub 
salts is found to be in conformity with the same law, one of the constituents be- 
ing always present in the proportion of two or more equivalents. 

The combining proportions of compound bodies depend entirely therefore up- 
on those of their constituents, or upon the equivalents of the elementary bodies. 
The mode of determining these fundamental equivalents generally consists, as 
may be anticipated, in ascertaining the quantity of any element which exists 
united with 100 parts of oxygen in the protoxide of that element, which quantity 
is viewed as a single equivalent. Thus of hydrogen and lead, the protoxides 
are water and litharge, in which respectively 100 oxygen are associated with 
12.5 hydrogen and 1294 lead, which numbers are therefore single equivalents 
of these elementary substances. But the difficulty still remains to know what 
is a protoxide : for the rule is not followed in all cases to consider that oxide of 
an element as the protoxide which contains the least proportion of oxygen. 
When only one oxide is known, it is presumed to be a protoxide and composed 
of single equivalents, unless it corresponds in properties with a higher degree of 
oxidation of some other element ; and of several oxides of the same element 
that containing least oxygen is viewed as the protoxide, unless a higher oxide 
has better claims to be considered as such. Hence magnesia and oxide of zinc 
being the only oxides of magnesium and zinc known are protoxides and water, 
litharge, potash, soda, lime, and protoxide of iron, which are all the lowest oxides 
of different metals, are admitted without objection to be protoxides, and become 
standards of comparison for this class of bodies; while alumina, the only oxide 
of aluminum, differing entirely from the protoxide of iron but closely resembling 
the peroxide of that metal, is considered a peroxide of similar constitution, or to 
contain three equivalents of oxygen and two of metal. Now in alumina 300 
oxygen, or three equivalents, are united with 342 aluminum, one half of which 
number, or 171, is therefore the equivalent of aluminum. The true protoxide 



COMBINING PROPORTIONS. 99 

of aluminum, if it is capable of existing, still remains to be discovered. The 
first degree of oxidation of chromium, or the green oxide, is likewise a peroxide 
and not a protoxide, being analogous to alumina and the peroxide of iron. On 
the other hand the second degree of oxidation of copper, or the black oxide, and 
not the first degree of oxidation of that metal, must be viewed as the protoxide, or 
as composed of single equivalents, from its correspondence with the protoxide of 
iron and a large class of admitted protoxides. The lower degree of oxidation of 
copper or the red oxide, which contains only half the proportion of oxygen in the 
black oxide, comes therefore to be considered a sub-oxide, or a compound of two 
equivalents of metal, and one of oxygen. For reasons somewhat similar the 
higher of the two grades of oxidation of mercury, or the red oxide of that metal, 
is now generally acknowledged to be the protoxide or to be composed of single 
equivalents, and the ash coloured oxide reputed a sub-oxide. These sub-oxides 
of mercury and copper are capable of combining with acids, but they are the 
only sub-oxides which possess that property. It is the character of protoxides 
to form salts with acids ; and of several oxides of the same metal, the protoxide 
is always the most powerful base. 

Bodies likewise replace each other in combination, in equivalent quantities. 
Thus in the decomposition of water by chlorine, which occurs in certain circum- 
stances, 442 parts of chlorine unite with 12.5 hydrogen or one equivalent of that 
body, to form hydrochloric acid, and displace at the same time and liberate 1 00 
parts of oxygen. Hence the number 442 represents the combining proportion 
of chlorine which is equivalent in combination to, or can be substituted for 100 
oxygen. Again in decomposing hydriodic acid, 442 chlorine unite with 12.5 
hydrogen, and liberate 1580 iodine, which proportion of iodine may again ac- 
quire 12.5 hydrogen by decomposing sulphuretted hydrogen and set free 201 
sulphur. Hence 1580 and 201 are the equivalent quantities of iodine and sul- 
phur, which take the place of 442 chlorine or 100 oxygen in combination with 
12.5 hydrogen. When 403 parts of zinc are introduced into a solution of nitrate 
of copper, they dissolve, acquiring 100 oxygen and 677 nitric acid, and become 
nitrate of zinc, while 396 parts of metallic copper are deposited, which had pre- 
viously been in the state of nitrate and in combination with the above-mentioned 
quantities of oxygen and nitric acid, and the solution remains otherwise unal- 
tered. Zinc throws down nearly all the metals from their solutions in acids in 
the same manner, and if the quantity of this substance introduced into the solu- 
tions and dissolved, be a combining proportion, as in the instance given, the 
quantities of the metals precipitated w'l also be combining proportions of those 
metals. The quantity of zinc employed may be varied, but the quantity of other 
metal precipitated will still be to the quantity of zinc dissolved, in the ratio of 
the combining numbers of the two metals. Lead, copper, tin, or any other metal, 
when it acts like zinc as a precipitant, likewise throws down equivalent quanti- 
ties of other metals, and takes their place in the pre-existing compound. The sub- 
stitution in a saline compound of one metal for another, which thus occurs, 
without any change in the character of the compound, shows how justly the 
combining proportions of bodies are also termed their equivalent quantities or 
equivalents. The metal displaced, and that substituted for it, have evidently the 
same value in the construction of the compound, and are truly equivalent to 
each other. 

The equivalent proportions of such oxides as are bases, are ascertained by 
finding what quantity of each saturates the known combining proportion of 
an acid. Thus to saturate 501 parts, or a combining proportion of sulphuric 
acid, the following proportions of different bases are requisite, and are equiva- 
lent in producing that effect : 

Magnesia - - - - 258 
Lime - 356 



100 COMBINING PROPORTIONS. 



Soda - 


. 


- 391 


Protoxide of manganese 


. 


- 445 


Potash - 


. 


- 590 


Strontian 


. 


- 647 


Barytes - 


, 


- 956 


Protoxide of lead 


. 


- 1394 


Oxide of silver 


- 


- 1451 



The addition of these bodies to sulphuric acid in the above proportions destroys 
its sour taste and other properties as an acid, of which the most characteristic 
is that of reddening certain vegetable blue colours such as litmus. The acid is 
said to be neutralized or saturated, and the product or compound formed is a 
neutral salt which does not alter the blue colour of litmus. Of the bases men- 
tioned, magnesia has the greatest saturating power, and oxide of silver the least ; 
the proportion of these bases necessary to saturate the same quantity of sulphu- 
ric acid being 258 of the former, and 1451 of the latter. 

Conversely the equivalent proportions of acids are the quantities which neu- 
tralize the known equivalent of any base or alkali. Thus 590 parts of potash, 
or a combining proportion is deprived of its alkaline properties, of which the 
most obvious are its caustic taste and power to restore the blue colour of red- 
dened litmus, by the following proportions of different acids, and a neutral com- 
pound or salt produced in every case : 

Sulphurous acid . . . . . 401 



501 

454.5 

677 

912 
1142 
2079 
2279 
among themselves in their 



Sulphuric acid 

Hydrochloric acid 

Nitric acid 

Chloric acid 

Hyperchloric acid 

Iodic acid 

Hyperiodic acid 
It thus appears that the acids differ as widely 
equivalent quantities as the bases do. The equivalent of either an acid or 
base thus deduced from its neutralizing power is always the same as that in- 
dicated by its composition, namely the sum of the equivalent numbers of its 
constituents. As the bases which saturate acids fully are all protoxides, it 
also necessarily follows that there are always 100 parts of oxygen contained 
in the proportion of base which neutralizes the equivalent of an acid. 

The equivalents of both acids and bases are likewise observed in those de- 
compositions in which one acid is substituted for another acid in combination, 
or one base for another base. Thus an equivalent of sulphuric acid is found 
to disengage the equivalent quantity exactly of sulphurous acid from the sul- 
phite of soda, of nitric acid from the nitrate of potash or of hydrochloric acid 
from the chloride of sodium, and to replace it in combination with the base, 
forming in every case a neutral sulphate. An equivalent of potash separates 
in like manner an equivalent of magnesia, of lime, of barytes or of protoxide 
of lead from its combination with an acid. The proportion of acid or base 
necessary to produce a certain amount of decomposition may therefore be cal- 
culated from a knowledge of the equivalents of bodies, and such knowledge 
comes to be of the most frequent and valuable application for practical pur- 
poses. 

But the substitution of equivalent quantities of different bodies for one 
another is most strikingly exhibited in the decompositions which follow the 
mixture of certain neutral salts. An equivalent of sulphate of magnesia being 
mixed with an equivalent of nitrate of barytes, the two bases exchange acids, 
the original salts disappear completely and two new salts are produced, the sul- 



COMBINING PROPORTIONS. 101 

phate of barytes which is insoluble and precipitates, and the nitrate of mag- 
nesia which remains in solution, as represented in the following diagram in 
which the equivalent quantities are expressed: 

Before decomposition. After decomposition. 

759 sulphate C 258 magnesia 935 nitrate of 

of magnesia { 501 sulphuric acid magnesia. 

1633 nitrate C 677 nitric acid 

of barytes £ 956 barytes 

1457 sulphate 
of barytes. 

After a double decomposition of this kind, the liquid remains neutral, or 
there is no redundancy of either acid or base, because each of the new salts is 
composed of a single equivalent of acid and of base like the salts from which 
they are formed. If one of the salts be added in a larger proportion than its 
equivalent quantity the excess does not interfere with the decomposition, and 
remains itself unaffected, the decomposition proceeding no farther than the 
equivalents present Hence the general observation that neutral salts continue 
neutral after decomposition, in whatever proportions they may be mixed. 

But the modes of fixing the equivalent numbers which have been stated are 
inapplicable to several elementary bodies, such as nitrogen, phosphorus, car- 
bon, boron, silicon and some metals, of which the protoxides are not bases 
and are uncertain. Nitrogen enters into nitric acid, of which acid it is 
known that the equivalent is 677, and that it contains five equivalents or 500 
parts of oxygen, and consequently 177 parts of nitrogen. It is doubtful, how- 
ever, whether 177 represents one or two equivalents of nitrogen. But 
the equivalent of ammonia likewise contains 177 nitrogen, and a less pro- 
portion is never found in the equivalent of any other compound into which 
that element enters. The number 177 is, therefore, the least combining 
proportion of nitrogen, and must on that account be taken as one equi- 
valent. The equivalent of phosphorus can be shown on the same principle 
to be 392.28, that of arsenic 940.08 and that of antimony 1612.90, as given 
in the tables, and not the halves of these numbers as commonly estimated. 
These three bodies agree with nitrogen in their chemical relations, and the 
numbers recommended represent the quantities which replace 177 nitro- 
gen in analogous compounds. The equivalent of carbon may be deduced 
from the known equivalent of its compound, carbonic acid. But the equi- 
valents of boron and silicon cannot be fixed upon with the same certainty, ow- 
ing to the doubt which hangs over the equivalents of boracic and silicic acids. 

Of the facts which involve the principle of combination in definite and equi- 
valent proportions the last-mentioned appears to have been the first observed 
and explained. Wenzel of Freyberg in Saxony so far back as 1777 made an 
analysis of a great variety of salts with surprising accuracy, which enabled him 
to perceive that the neutrality which is observed after the mutual decomposition 
of neutral salts depends upon this, that the quantities of different acids which 
saturate an equal weight of one base will also saturate equal weights of any 
other base. 

Richter of Berlin confirmed and extended the observations of Wenzel, attach- 
ing proportional numbers to the acids and bases, and remarking for the first 
time that the neutrality does not change during the precipitation of metals by 
each other, and also that the proportion of oxygen in the equivalents of bases 
is the same in all, and may be represented by 100 parts. But the first founda- 
tions of a complete system of equivalents embracing both simple bodies and 
their compounds were laid by Dalton, at the same time that he announced his 

9* 



102 COMBINING PROPORTIONS. * 

atomic theory .* The observation that the equivalent of a compound body is 
the sum of the equivalents of its constituents, and the discovery of combination 
in multiple proportions are peculiarly his. Dr. Wollaston afterwards adapted 
the more important equivalents to the common sliding rule of Gunter, by means 
of which, proportions can be observed without the trouble of calculation. This 
instrument, which is known under the name of the scale of chemical equivalents, 
contributed largely to the diffusion of the knowledge of the proportional numbers, 
but is not itself of much practical value. 

The numerical accuracy of the equivalents assigned to bodies, depends en- 
tirely upon the exactness of the chemical analyses from which they are deduced. 
The generally received series of numbers, which is adopted in this work, was 
drawn up by Berzelius from data supplied in a great measure by himself. The 
consideration of the laws of Wenzer and Richter, which were long overlooked 
or misunderstood, was revived by him, and by a series of analytical researches 
unrivalled for their extent and accuracy he first impressed upon chemistry the 
character of a science of number and quantity, which is now its highest recom- 
mendation. Several of Berzelius's numbers received a valuable confirmation 
from Dr. Turner, whose inquiries were especially directed to test an hypothesis 
respecting them, advocated by some of his contemporaries ; namely, that the 
equivalents of all the elements are multiples of the equivalent of hydrogen, and 
consequently if that equivalent be made equal to 1, all the others will be whole 
numbers. Dr. Turner's results are incompatible with such a relation among 
the equivalent numbers, the existence of which indeed is disproved by all ac- 
curate analyses, f 

Still the existence of a simple relation between certain equivalents has been 
pointed out by M. Dumas; and it is possible that the numbers of each of the 
pairs below, which approach so closely, would actually coincide, as they do in 
one pair, were they determined with absolute accuracy. 

Cobalt .... 368.99 Platinum .... 1233.5 

Nickel .... 369.68 Iridium .... 1233.5 

Osmium . . . 1244.49 Sulphur .... 201.17 

Gold . . . 1243.01 ±Eq. Tellurium. . . 200.44 

But these are the only equivalents between which there are good grounds for 
supposing that any relation exists. The identity of the atomic weights of pla- 
tinum and iridium is the most certain, having been experimentally confirmed by 
Berzelius since it was first asserted by Dumas. 

Of the two series of numbers given in the tables, the first in which oxygen is 
made equal to 100, and which is called the oxygen series, is called the most 
convenient, and will alone be made use of in the following pages. The numbers 
of this series are so large that the fractional portion may, I believe, be safely 
neglected in computing them, being within the unavoidable errors of observation 
in chemical analyses, and the nearest whole number may be adopted, except in 
the following equivalents, although even in them it is unnecessary to go beyond 
the first decimal figure : 

Hvdrogen . . . . . 12.5 

Carbon 76.4 

Chlorine 442.6 

Lead 1294.5 

The numbers belonging to the other or hydrogen series, are all twelve and 
a half times less than the corresponding numbers of the oxygen series, into 
which the former may most easily be converted by multiplying them by one 



* New System of Chemical Philosophy, 1807. 
t Philosophical Transactions, 1833, p. 523. 



ATOMIC THEORY. 103 

hundred, and dividing the product by eight. Or the numbers of the oxygen 
may be reduced to the hydrogen scale, which many prefer, by dividing them 
by one hundred and multiplying the quotient by eight. The numbers of the 
hydrogen scale are of a lower term, smaller and more easily recollected than 
the oxygen series, but their fractional portion can seldom be neglected in com- 
puting by means of them, and the insecurity of the basis on which this series 
rests is a great objection to its adoption. There is an actual experimental 
difficulty in determining the equivalent of hydrogen with precision, arising 
from its extreme smallness; so that this equivalent itself is more liable to cor- 
rection and alteration than most others, which would necessitate a correspond- 
ing change throughout the whole scale. 



ATOMIC THEORY. 

The laws of combination and the doctrine of equivalents which have just 
been considered, are founded upon experimental evidence only, and involve no 
hypothesis. The most general of these laws were not however suggested bv 
observation, but by a theory of the atomic constitution of bodies, in which 
they are included, and which affords a luminous explanation of them. The 
partial verification which this theory has received in the establishment of these 
laws, adds greatly to its interest, arid is a strong argument in favour of its 
truth. It is the atomic theory of Dalton, the essential part of which may be 
stated in a few words. 

Although matter appears to be divided and comminuted in many circum- 
stances to an extent beyond our powers of conception, it is possible that it 
may not be indefinitely divisible; that there may be a limit to the successive 
division or secability of its parts, a limit which it may be difficult or impossi- 
ble to reach by experiment, but which nevertheless exists. Matter may 
therefore be composed of ultimate particles or atoms, which are not farther 
divisible, and each of which possesses a certain absolute and possibly appre- 
ciable weight. Now the question arises, is the atom in every kind of matter 
of the same weight, or do atoms of different kinds of matter differ in weight? 
Are the ultimate particles, for instance, to which charcoal and sulphur are 
reducible, of the same or of different weights? Let their weights be sup- 
posed to be different, to be in the proportion of the equivalent numbers of sul- 
phur and charcoal, which thus become atomic weights, and so of the atoms 
of other elementary bodies, and the whole laws of combination follow by the 
simplest reasoning. The atoms of the elementary bodies may be represented 
to the eye by spheres or by circles in which their symbols are inscribed to 
distinguish them, as in the following examples, with their relative weight3. 
Names. Alnms - Weight of atoms. 

Oxygen . . • © • ■ • • 100 
Hydrogen . . . (ft) . . . . 12.5 

Nitrogen ... (g) .... 177 
Carbon . . . (g) ... 76.4 

Sulphur ... (g) .... 201 
Lead. •••©•••• 1294 - 5 

Chemical combination takes place between the atoms of bodies, which then 
come into juxta-position; and in decomposition the simple atoms separate 
again from each other, in possession of their original properties. The atom 



104 



ATOMIC THEORY. 



or integrant particle of a compound body is an aggregation of simple atoms, 
and must therefore have a weight equal to the sum of their weights, as will 
be obvious from the exhibition of the atomic constitution of a few compounds. 



Water (oxide of hydrogen) ®@ 



Protoxide of nitrogen 
Deutoxide of nitrogen 
Sulphuric acid . 
Oxide of lead . 

Sulphate of lead 



• -CD®©® 




12.5+100= 112.5 

177 +100= 277 

177 -f200= 377 

201 4300= 501 

1294.5 +100=1394.5 

1394.5 4501 = 1895.5 



It is unnecessary to make any assumption as to the nature, size, form,, or 
even actual weight of the atoms of elementary bodies, or as to the mode in 
which they are grouped or arranged in compounds. All that is known or 
likely ever to be known respecting them is their relative weight. The atom 
of oxygen is eight times heavier than that of hydrogen, or they are to each 
other as 100 to 12.5, but their actual weights are undetermined. To afford 
the means of expressing the relative weights of these and other atoms, a num- 
ber which is entirely arbitrary is assigned to one of them, namely 100 to the 
atom of oxygen, and then the weight of the atom of hydrogen can be said to 
be 12.5, of nitrogen 177, of carbon 76.4, of sulphur 201, and of lead 1294.5. 
A single atom of water contains one atom of oxygen, (100) and one of hydro- 
gen, (12.5) and must therefore weigh 112.5; an atom of oxide of lead con- 
tains one atom of oxygen and one of lead, which weigh together 1394.5; an 
atom of sulphuric acid, one atom of sulphur and three atoms of oxygen, which 
weigh together 501; and an atom of sulphate of lead, including one of each 
of the preceding compound atoms must weigh 1394.54 501, or 1895.5. 

The equivalent quantities being now represented by atoms, it necessarily fol- 
lows that bodies can combine in these quantities or multiples of them only, 
and not in intermediate proportions, for atoms do not admit of division. In a 
series of several compounds of the same elements, such as the oxides of nitrogen, 
which was formerly referred to in illustration of combination in multiple pro- 
portions, (page 96) one atom of nitrogen combines with one, two, three, four, 
and five atoms of oxygen, and a simple ratio between the quantities of oxygen 
in these compounds is the consequence. The equivalent of a compound body 
also is the sum of the equivalents of its constituents, for the weight of a com- 
pound atom is the weight of its constituent atoms. 

By the juxta-position, separation and exchange of one atom for another in 
compounds, all kinds of combination and decomposition in equivalent quantities 
may be produced, while the substitution of ponderable masses for the abstract 
idea of equivalents renders the whole changes most readily conceivable. 

This theory being adopted as a useful, while it is at the same time, a highly 
probable representation of the laws of combination, its terms, atom, and atomic 
weight may be used as synonymous with equivalent, equivalent quantity and 
combining proportion. 

M. Dumas is disposed to modify the atomic theory so far as to allow the di- 
visibility of the atoms or ultimate masses in which a body enters into combi- 
nation, and to suppose that they are groups of more minute atoms, into which 
they may be divided by physical, but not by chemical forces. He distinguishes 
the atoms which correspond with equivalents as chemical atoms, and allowing 
them to represent truly and constantly the least quantities in which bodies com- 



SPECIFIC HEAT OF ATOMS. 



105 



bine, still supposes that under the influence of heat and perhaps other physical 
agencies, these molecules may be subdivided into atoms of an inferior order, of 
which, for example, two, four or a thousand are included in a single chemical 
atom.* But surely such a view is entirely subversive of the atomic theory. It 
is principally founded on the assumed existence of a similarity between atoms 
in their capacity for heat, and in their volume while in the gaseous state, in 
which it would be more natural to admit a difference among different atoms. 



SPECIFIC HEAT OF ATOMS. 

The quantity of heat necessary to raise the temperature of equal weights of 
different bodies a single degree, varies according to their nature, and may be 
expressed by numbers which are the capacities for heat or specific heats of these 
bodies (page 40.) This difference appears in the numbers of several simple 
bodies placed together in the first column of the table below, among which no 
relation can be perceived. But if the comparison is made between' the capacity 
for heat not of equal weights but of atomic weights or equivalent quantities of 
the same bodies, as in the second and third columns of the table, then the num- 
bers for several bodies are found to be nearly the same, and those of others to 
bear a simple relation to each other. 



SPECIFIC HEAT. 



Lead 

Tin 

Zinc 

Copper 

Nickel 

Iron 

Platinum 

Sulphur 

Mercury 

Gold 

Tellurium 

Arsenic 

Silver 

Phosphorus 

Iodine 

Cobalt 

Carbon 

Bismuth 



1. 

Of equal 

weights. 

Specific heat 
of same 
weight of wa- 
ter being 1. 
0.0293 
0.0514 
0.0927 
0.0949 
0.1035 
0.1100 , 
0.0314 , 
0.1880 , 
0.0330 
0.0149 
0.0912 . 
0.081 
0.0557 , 
0.385 , 
0.089 , 
0.1498 , 
0.25 
0.0288 . 



1294.5 
735 

403 
396 
370 
339 

1234 
201 

1266 

1243 
802 
940 

1352 
392 

1580 
369 

76.4 
887 

Of the first ten substances which are all metals, with the exception of sul- 
phur, the capacities of the atoms approach so closely, that they may be con- 
sidered as identical; their capacities appearing to be all nearly one-third of that 
of the atom of water, in the second column; and nearly coinciding with the 

*Lepons sur la Philosophic Chimique, professees au College de France, par M. Dumas, 
page 233. Paris, 1837. 



II. 

Of atoms. 

Specific heat 

of atom 

of water being 

1. 

. 0.3372 . 

, 0.3358 . 

, 0.3321 . 

, 0.3340 . 

, 0.3404 . 

0.3315 . 

0.3443 . 

0.3359 . 

, 0.3714 . 

, 0.3292 . 

0.6501 . 

0.6768 . 

0.6694 . 

1.3415 . 

1.2500 . 

0.4914 . 

0.1698 . 

0.2271 . 



III. 

Of atoms. 



Specific heat 

of atom 
of lead being 

1. 

1.0000 . 

0.9960 . 

0.9850 . 

0.9908 . 

1.0095 . 

0.9831 . 

1.0211 . 

0.9963 . 

1.1015 . 

0.9765 . 

1.9283 . 

2.0074 . 

1.9855 . 

3.9789 . 

3.7074 . 

1.4574 . 

0.5036 . 

0.6736 . 



IV. 

Atomic 
weights. 



106 



SPECIFIC HEAT OF ATOMS. 



capacity of the atom of lead, one of their number in the third column. The 
weights of the atoms themselves are added in a fourth column for convex 
nience of reference. The ten substances in question, taken in the propor- 
tions of their atomic weights will, therefore, undergo an equal change of 
temperature on assuming an equal quantity of heat. The three metals which 
follow in the table, namely, tellurium, arsenic, and silver, appear to have an 
equal capacity for heat, which is double that of lead, and the class which coin- 
cides with it, while the capacity of phosphorus and iodine is four times 
greater than that of lead and its class. The capacity of the atom of cobalt ap- 
pears to be once and a half, and that of the atom of carbon to be one-half of 
that of lead. But bismuth appears to have no clear relation to the others, the 
capacity of its atom being 0.6736, referred to that of lead as 1. The general 
results, therefore, may be stated as follows: 
Specific heat of atom of lead 



11 11 


11 


tin 




11 11 


11 


zinc 




■■is 

11 11 


11 


copper 




11 11 


11 


nickel 




11 11 


11 


iron 




11 11 


11 


platinum 




11 11 


11 


sulphur 




11 11 


11 


mercury 




11 11 


11 


gold 




11 11 


11 


tellurium 


2 


11 11 


11 


arsenic 


2 


11 11 


11 


silver 


2 


11 11 


11 


phosphorus . 


4 


11 11 


11 


iodine 


4 


11 11 


11 


cobalt 


If 


11 11 


11 


carbon 


.2 



Messrs. Dulong and Petit, whose researches supplied these valuable results, 
drew a more general conclusion from them, namely that all atoms, or at least 
all simple atoms, have the same capacity for heat, and that those atomic 
weights which are inconsistent with that supposition, ought to be altered and 
accommodated to it. The specific heat of a body would thus afford the means 
of fixing its atomic weight. Some of the alterations in the atomic weights, 
which would follow the adoption of this law, might be advocated upon other 
grounds, such as halving the atomic weight of silver, but certain other changes 
equally inevitable are wholly inadmissible; such as dividing the atom of tellu- 
rium by two, or reducing it from 802 to 401, although the most perfect analogy 
subsists between tellurium and sulphur in their compounds, in all of which 
802 parts tellurium, and not 401, replace 201 sulphur or one equivalent. The 
equivalent of phosphorus would require to be divided by four, while that of 
arsenic which it so closely represents in compounds, is divided only by two. 
Of the admitted equivalents of nickel and cobalt also, which replace each other 
in analogous compounds, the first remains unaltered, while the last must be 
reduced to two-thirds of its present amount. 

It must be concluded then, that elementary atoms have not necessarily the 
same capacity for heat, although a simple relation appears always to exist be- 
tween their capacities. The capacities of the three gaseous elements, oxygen, 
hydrogen and nitrogen, may likewise be adduced in support of such a relation, 
provided they are the same for equal volumes of the gases, agreeably to the ob- 
servations of Dulong. But this relation can only be looked for between bodies 
while under the same physical condition, and perhaps agreeing in other circum- 



VOLUMES OF ATOMS IN THE GASEOUS STATE. 



107 



stances also, for the capacity for heat of the same body is known to vary under 
the different forms of solid, liquid and gas; and, indeed, while the body is in the 
same state, its capacity appears not to be absolutely constant, but to increase 
perceptibly at elevated temperatures (page 40.) 

The capacities of compound atoms have not been submitted to a sufficiently 
extensive examination to determine whether equally simple relations subsist ge- 
nerally among them. In two classes of analogous combinations, however, the 
capacities of the atoms for heat have been found by M. Neumann to approach 
so closely, that they may be admitted to be the same, the differences being suf- 
ficiently accounted for by the errors of observation unavoidable in such delicate 
researches. 





Of equal weights. 


Of atomic weights. 




Specific heat of 


Specific heat of 




same weight of 


atom of water 




water being 1. 


being 1. 


Carbonate of lime . 


0.2044 


0.1148 


Carbonate of barytes 


0.1080 


0.1181 


Carbonate of iron . 


0.1819 


0.1156 


Carbonate of lead 


0.0810 


0.1200 


Carbonate of zinc 


0.1712 


0.1187 


Carbonate of strontian . 


0.1445 


0.1184 


Dolomite (carbonates of lime 


and 




magnesia) 


0.2111 
Mean 


0.1121 




0.1168 


iall class of sulphates presente 


d a similar result : 






Of equal weights. 


Of atomic weights. 


Sulphate of barytes 


0.1068 


0.1384 


Sulphate of lime . 


0.J854 


0.1412 


Sulphate of strontian • . 


0.1300 


0.1326 


Sulphate of lead . 


0.0830 


0.1398 



Mean . 0.1380 . 
The numbers in the second column of both tables, deviate very little from 
their mean, but there is no relation between the two means. Identity in capa- 
city for heat is, therefore, to be looked for in compound atoms of the same na- 
ture, and which closely agree in their chemical relations, like the numbers of 
each group, but not between compound atoms which are differently constituted. 



RELATIONS BETWEEN THE ATOMIC WEIGHTS AND VOLUMES OF 
BODIES IN THE GASEOUS STATE. 



Several of the elementary bodies are gases, such as oxygen, hydrogen, nitro- 
gen and chlorine, and the proportions in which they combine can be determined 
by measure with equal, if not greater facility than by weight. A relation of the 
simplest nature is always found to subsist between the measures or volumes in 
which any two of the gaseous elementary bodies unite. This arises from the 
circumstance that the specific gravities of gases either correspond exactly with 
their atomic weights or bear a simple relation to them. The atom of 
chlorine is 35| times heavier than that of hydrogen; and chlorine gas is 
35 £ times heavier than hydrogen gas, so that the combining measures of these 
two gases, which correspond with single equivalents, are necessarily equal. The 
atom of nitrogen, and its weight as a gas being both 14.2 times greater than the 
atom and weight of hydrogen gas, their combining volumes must be the same. 



108 VOLUMES OF ATOMS IN THE GASEOUS STATE. 

The atom of oxygen is eight times heavier than that of hydrogen, but oxygen 
gas is sixteen times heavier than hydrogen gas, so that taken in equal volumes 
these two gases are in the proportion by weight of two equivalents of oxygen 
to one of hydrogen. Hence, in the combination of single equivalents of these 
elements to form water, half a volume or measure of oxygen gas unites with a 
whole volume or measure of hydrogen gas. One volume of nitrogen, also unites 
with half a volume of oxygen, and with a whole volume of the same gas, to form 
respectively the protoxide and deutoxide of nitrogen. 

The exact ratio of one to two in which oxygen and hydrogen gases combine 
by measure, was first observed by Humboldt and Gay-Lussac in 1805. The 
subject was pursued by the latter chemist, who established the simple ratios in 
which gases generally combine, and published the laws observed by him, or his 
Theory of Volumes, shortly after the announcement of the Atomic Theory by 
Dalton. They afforded new and independent evidence of the combination of 
bodies in definite and also in multiple proportions, equally convincing as the ob- 
served proportions by weight in which bodies unite. Gay-Lussac likewise ob- 
served that the product of the union of two gases, if itself a gas, sometimes re- 
tains the original volume of its constituents, no contraction or change of volume 
resulting from their combination ; thus one volume of nitrogen and one volume 
of oxygen form two volumes of deutoxide of nitrogen ; one volume of chlorine 
and one volume of hydrogen, form two volumes of hydrochloric acid gas ; and 
that when contraction follows combination, which is the most common case, the 
volume of the compound gas always bears a simple ratio to the volumes of its 
elements. Thus two volumes of hydrogen and one of oxygen form two volumes 
of steam, one volume of nitrogen, and three of hydrogen gas form two volumes 
of ammoniacal gas, one volume of hydrogen and one-sixth of a volume of sulphur- 
vapour form one volume of sulphuretted hydrogen gas. In these and all other 
statements respecting volumes, the gases compared are supposed to be in the 
same circumstances as to pressure and temperature. 

The uniformity of properties observed among gases in compressibility and 
dilatability by heat, has appeared to many chemists to indicate a similarity of 
constitution, and to favour the idea that they all contain the same number of 
atoms in the same volume. May not equal volumes of oxygen and hydrogen 
gases, for instance, be represented by an equal number of atoms of oxygen 
and hydrogen respectively placed at equal distances from each other, and the 
difference of sixteen to one in the densities of the two gases arise from the 
atom of oxygen being really sixteen times heavier than that of hydrogen? 
Equal volumes of gases would then contain an equal number of atoms, and 
one, two or three volumes would be an equivalent expression to one, two 
or three atomic proportions, the terms volume and atom becoming of the 
same import, or expressing equal quantities of bodies. But such a view 
is obviously inapplicable to compound gases, as their volume has a variable 
relation to that of their elements; and its adoption would require grave altera- 
tions to be made in the atomic weights of several of the elements themselves, 
to accommodate these weights to the observed densities of the bodies in the 
gaseous state. This will be seen from the following table, in which the 
volume or fractional part of a volume placed against each element always con- 
tains the same number of its presently received atoms. These volumes are, 
therefore, the equivalent volumes of the elements, and may be viewed as re- 
presenting the bulk of their atoms in the gaseous state, the combining volume 
of hydrogen being here taken as one. 



VOLUMES OF ATOMS IN THE GASEOUS STATE. 



109 



ATOMS. 



Hydrogen 

Nitrogen 

Chlorine 

Bromine 

Iodine 

Oxygen 

Phosphorus 

Arsenic 

Sulphur 

Mercury 



Volume. 
1 






weight. 
12.5 


1 


. 


. 


177 


1 


. 


. 


442.6 


1 


. 


. , 


978 


1 


. 


. 


. 1580 


i 


. 


. 


100 


i 
a 


. 


. 


392 


i 

2 


. 


. 


940 


i 


. 


. 


201 


2 


. 


. 


. 1266 



Of the first five bodies enumerated, equivalent weights occupy equal volumes. 
It was indeed the observation of this equality between the atom and volume in 
these gases, that led to the supposition of that relation being general. But 
the atoms of oxygen, phosphorus and arsenic occupy only half a volume, and 
would require to be doubled to fill the same volume as the preceding class. 
The present atom of sulphur affords only one-sixth of a volume of vapour, 
and must, therefore, be multiplied by six to afford a whole volume; while the 
atom of mercury supplies two volumes of vapour, and would, therefore, re- 
quire to be divided by two, or reduced to one-half of its present number. 
Of these changes the required modification of the atoms of phosphorus, arsenic 
and sulphur is incompatible with their chemical relations to other bodies 
which are best established, and is quite inadmissible. The densities of the 
vapours of these bodies must, therefore, be viewed as decisive against the 
equality of the equivalent volumes of the elementary gases. A volume of 
sulphur vapour must be allowed to contain three times as many atoms as an 
equal volume of oxygen gas, six times more than the same volume of hydro- 
gen gas, and twelve times more than the same volume of mercury vapour. 
A similar constitution cannot be assigned to these vapours, unless on the as- 
sumption of Dumas, that chemical atoms of the same kind may group together, 
and form larger compound atoms or molecules, or divide into smaller mole- 
cules. The molecule of hydrogen in the gaseous state being the same as its 
chemical atom, each molecule of oxygen while in the state of gas would be 
an aggregate of two chemical atoms, and each of sulphur of six; while mer- 
cury must suffer molecular division in the state of vapour, each of its chemical 
atoms being parted into two, in order that equal volumes of these different 
gases and vapours should contain the same number of molecules or atoms. 
But such views are entirely speculative. 

In the farther consideration of the proportions in which gases combine by 
measure, it will be found conducive to perspicuity to adopt the combining vo- 
lume of oxygen, as the unit (instead of that of hydrogen as in the last table,) in 
terms of which to express the combining measures of other gases, both simple, 
and compound. The combining,measure of oxygen being one volume, the 
combining measure of hydrogen and its class will be two volumes ; or the atom 
of oxygen gives one and the atom of hydrogen two volumes of gas. Volumes 
of the gases may be represented by equal squares with their relative weights 
inscribed, the numbers having reference to the number assigned to the oxygen 
volume. If that number be 100, or the atomic weight of oxygen, as in column 
I of the table below, then the number to be inscribed in each of the two volumes 
forming the combining measure of hydrogen will be 6.25 or half its atomic 
weight, the combining measure itself having the full atomic weight of hydro- 
gen, namely 12.5 ; and so of other gases, the combining measure has the whole 
10 



110 



VOLUMES OF ATOMS IN THE GASEOUS STATE. 



atomic weight which is divided among the component volumes. But there is 
the reason for preferring the number 1102.6 to 100 for the standard oxygen 
volume that the weight of a volume of air being taken as 1000, that of an equal 
volume of oxygen is 1102.6 ; and consequently the corresponding number for 
the volume of hydrogen, 69 expresses the relation in weight of that gas also to 
air, and so do the corresponding numbers for all the other gases. The numbers 
on this scale, which express the relative densities of a volume of each gas, and 
are inscribed in the squares of column II, are indeed the common specific gravi- 
ties of the gates. 



Oxygew 



Phosphorus . 



Hydrogen 



Chlorine 



I 

Momic weight. C 


'ombining 
measure. 


II. 

Combmin 


r measure 




Air. 


1000 
















100 


100 






1102.6 





















392 


392 




. 


4327 




.12.5 


6.25 
6.25 


1 


69 
69 
















. 442.6 . 


221.3 
221.3 




. 


2470 
2470 
















1266 


316.5 ! 


316.5 






6969 .' 6969 




316.5 .' 


316.5 


6969 '. 6969 

















Mercury 



The double squares which represent the combining measures of hydrogen and 
chlorine are divided into volumes by dotted lines to show that the division is 
imaginary, the partition of a combining measure, like that of an atom which it 
represents, being impossible, the specific gravities of gases being merely the 
relative weights of equal volumes, may be expressed by the numbers in the 
squares of the first column ; and the specific gravity of oxygen being according- 
ly made 100, the specific gravity of any other gas will either be the same num- 
ber as its atomic weight or an aliquot part of it. Or if the specific gravity of 
oxygen be made 1 or 1000, the relation of densities to atomic weights will still 
be very obvious. 

The combining measures of compound gases, although variable, have still a 



VOLUMES OF ATOMS IN THE GASEOUS STATE. 



Ill 



constant and a simple relation to each other, such as 1 to 1, 1 to 2, or 2 to 3; 
their elements in combining suffering either no condensation, or a definite and 
very simple change of volume. Hence the density of a compound gas may 
often be calculated with more precision from the densities of its constituents 
and a knowledge of the change of volume, if any, which occurred in combi- 
nation, than it can be determined by experiment. 

To deduce on this principle the specific gravity of steam. It consists of 
single equivalents of oxygen and hydrogen, of which the combining measure 
of the first is one, and that of the second two volumes. These three volumes, 
weigh 11 02. 6 +69 + 69 == 1240.6, and they form two volumes of steam; of 
which one volume must, therefore, weigh 1240.6 divided by two, or 620.3, 
which is, consequently, the calculated specific gravity of steam, referred to 
that of air as 1000. The relations in volume of the gases before and after 
combination may be thus exhibited. 



Combining measure, or 
one volume of oxygen. 



Combining measure, or 
two volumes of hydrogen. 



Combining measure, or 
two volumes of steara. 



102.6 



69 
6!) 



620.3 



620.3 



1240.6 1240.6 

It thus appears necessary to inscribe 620.3 in each volume of steam, to make 
up 1240.6, the known weight of the two volumes. 

In the formation of the hydrochloric acid, equal measures of chlorine and 
hydrogen unite without condensation, so that the product possesses the united 
volumes of its constituent gases. 



Combining measure 

of hydrogen or two 

volumes. 



Combining measure 

of chlorine or two 

volumes. 



Combining measure of 
hydrochloric acid or four 
volumes. 



6!) 



G9 



4- 



2470 



2470 



1269.5 • 1269.5 



1269.5 : 1269.5 



5078 



5078 



The specific gravity or weight of a single volume of hydrochloric acid is, 
therefore, obtained by dividing 5078 by 4, and is 1269.5. 

The specific gravity of the vapour of an elementary body, which there are 
no means of ascertaining experimentally, may sometimes be calculated from 
the known density of a gaseous compound containing it. The density of 
carbon vapour may be thus deduced from the observed density of carbonic 
oxide gas. Assuming that the combining measure of carbon is double that of 
oxygen, as is true of hydrogen and several other elementary bodies, then car- 
bonic oxide, which like water consists of single equivalents of its constituents, 
will resemble steam in its constitution also, and be composed of one volume 
of oxygen gas and two volumes of carbon vapour condensed into two volumes. 
The weight of a single volume of carbonic oxide being 972.8, two volumes, 
(1945.6) may be resolved, as shown in the diagram below, into one volume 
of oxygen, 1102.6, and two volumes of carbon-vapour, 843., (1945.6 — 1102.6 
= 843) each of which it follows must weigh 421.5. 



112 



VOLUMES OF ATOMS IN THE GASEOUS STATE, 



Combining measure or 

two volumes of carbonic 

oxide. 



Combining measure or 
one volume of oxygen. 



Combining measure or 
two volumes of carbon 
vapour. 



972.8 
972.8 






. = . 


1102.6 







421.5 
421.5 



1945.6 1945.6 

But the density 421.5 thus assigned to carbon vapour will only be true if it 
corresponds with hydrogen in its combining measure; but the combining mea- 
sure of carbon vapour may as well be one-half that of hydrogen, like that of 
phosphorus, or one-sixth like that of sulphur, and then the density will be 
double or six times that supposed. The important conclusion, however, that 
the density of carbon vapour is either 421.5, or some multiple or sub-multiple 
of that number is quite certain. 

The two following tables comprise nearly all the accurate information which 
chemists at present possess respecting the specific gravities of gaseous bodies. 
The bodies placed in the first table are generally considered as belonging to 
the inorganic and those in the second, to the organic department of the science. 



VOLUMES OF ATOMS IN THE GASEOUS STATE. 



113 



TABLE I. 









DENSITY. 


ATOM. 


GASES AND VAPOURS. 




Volumes in 






Air = 1000. 


combining 
measure. 


Weight. 


Oxygen 


1102.6 


1 


100 


Phosphorus ..... 


4327 


1 


392.28 


Arsenic .... 






10370 


1 


940.08 


Arsenious acid . 






13678 


1 


1240.08 


Sulphuret of mercury 


. 




5384 


2 
1 


1466.99 


Sulphur .... 






6648 


1 


201.17 


Hydrogen .... 






69 


2 


12.50 


Nitrogen .... 






976 


2 


177.04 


Carbon (hypothetical) 






421.5 


2 


76.44 


Chlorine .... 






2470 


2 


442.65 


Iodine 






8707 


2 


1579.50 


Bromine . . ... 






5393 


2 


978.31 


Water 






620.2 


2 


112.50 


Protoxide of nitrogen . 






1527.3 


2 


277.04 


Carbonic oxide 






972.8 


2 


176.44 


Carbonic acid 






1524.1 


2 


276.44 


Sulphurous acid 






2210.6 


2 


401.17 


Sulphuric acid (anhydrous) . 






2761.9 


2 


501.17 


Sulphuretted hydrogen . 






1177 


2 


213.67 


Light carburetted hydrogen 






559.5 


2 


101.44 


Cyanogen .... 






1819 


2 


329.92 


Mercury .... 






6978 


o 


1265.82 


Deutoxide of nitrogen . 






1039.3 


4 


377.04 


Hydrochloric acid 






1269.5 


4 


455.13 


Hydriodic acid . 






4385 


4 


1592.00 


Hydrobromic acid . 






2731 


4 


990.81 


Hydrocyanic acid 






944 


4 


342.42 


Ammonia .... 






591. 


4 


214.54 


Arsenuretted hydrogen 






2695 


4 


977.58 


Terchloride of arsenic 






6295 


4 


2268.053 


Teriodide of arsenic 






15640 


4 


5678.58 


Subchloride of mercury . 






8204 


4 


2974.29 


Chloride of mercury . 






9439 


4 


1708.47 


Subbromide of mercury . 






9665 


4 


3509.95 


Bromide of mercury . 






12362 


4 


2244.13 


Iodide of mercury (red) . 






15680 


4 


2845.32 



10* 



114 



VOLUMES OF ATOMS IN THE GASEOUS STATE. 

TABLE II. 





| 


DENSITY. 


Volumes 




GASES AND VAPOURS. 


FORMULA. 


Air = 


1000. 


in 

ombing. 
neasure. 


OBSERVER. 




[Calculated. 


Observed. 




Ether 


C 4 H s O 


2583 


2586 


2 


Gay-Lussac. 


Methylic Ether .... 


C 2 H 3 


1601 


1617 


2 


Dumas &Peligot. * 


Sulphate of methyl . . . 


C 2 H 3 0,S0 3 


4364 


4565 


2 


Idem. 


Oxalic ether 


C 4 H,0,C 2 3 


5081 


5087 


2 


Dumas & Boullay. 


Succinic ether ..... 


C 4 H S 6,C 4 H 2 3 


6201 


6220 


2 


Felix d'Arcet. 


Oenanthic ether .... 


C 4 H 5 0,C l4 H 13 2 


10477 


10508 


2 


Liebig & Pelouze. 


Alcarsine 


C 4 H 6 As O 


7833 


7555 


2 


Bunsen. 


Acetic Acid 


C 4 H 4 4 


2778 


2770 


3 


Dumas. 


Methyl 


C 2 H 3 


525 




4 


Dumas & Peligot 


defiant gas 


C 4 H 4 


981 


985 


4 


M. de Saussure. 


Gas from oil 


C 8 H 8 


1962 


1892 


4 


Faraday. 


Oleene . 


Ci 2 H 12 


2942 


2875 


4 


Fremy. 


Elaene . 


CjsHj 3 


4156 


4071 


4 


Idem. 


Cetene ....... 


C32H32 


7943 


8007 


4 


Dumas & Peligot. 


Benzin 


C 1 2 H 6 


2736 


2770 


4 


Mitscherlich. 




C l4 H 8 


3226 


3230 


4 


PeJletier& Walter. 


Retinyle 


C l8 H i2 


4247 


4242 


4 


Jdem. 


Retinole 


C^Hj 6 


7290 


7110 


4 


Idem. 


Naphthaline 

Paranaphthaline .... 


C 20 H 3 


4488 


4528 


4 


Dumas. 


C 3 1 ' 1 2 


6732 


6741 


4 


Dumas & Laurent. 


Camphene or oil of turpentine 


C 2 oHi 6 


4763 


4765 


4 


Dumas. 


Camphor 


C 2 ofi60 2 


5314 


5468 


4 


Idem. 


Menthene (from oil of mint) 


^2 0^18 


4830 


4940 


4 


Walter. 


Concrete essence of mint . 


V20" 2 o0 2 


5450 


5620 


4 


Idem. 


Wood spirit 


C 2 H 4 2 


1110 


1120 


4 


Dumas & Peligot. 


Hydrochlorate of methylene 


C 2 H 3 C1 


1738 


1731 


4 


Idem. 


Hydrofluate of methylene 


C 2 H 3 F 


1169 


1186 


4 


Idem. 


Hydriodate of methylene . 


C 2 H 3 l 


4882 


4883 


4 


Idem. 


Nitrate of methyl .... 


C 2 H 3 0,N0 3 


2667 


2653 


4 


Idem. 


Formate of methyl . . . 


C 2 H 3 0,C 2 H0 3 


2083 


2084 


4 


Idem. 


Acetate of methyl . . . 


C 2 H 3 0,C 4 H 3 3 


2573 


2563 


4 


Idem. 




C 4 H 6 2 


1601 


1613 


4 


Gay-Lussac. 


Mercaptan 


C 4 H 6 S 2 


2158 


2326 


4 


Bunsen. 


Hydrochloric ether . . . 


C 4 H 5 Cl 


2229 


2219 


4 


Thenard. 


Hydriodic ether .... 


c 4 h 5 i 


5321 


5475 


4 


Gay-Lussac. 


Nitrous ether 


C 4 H 5 0.N0 3 


2606 


2626 


4 


Dumas & Boullay. 


Chloroxicarbonic ether . . 


C 4 H 5 0,C 2 3 CI 


3759 


3829 


4 


Dumas. 




C 4 H 5 0,C 4 H 3 3 


3066 


3067 


4 


Idem. 


Benzoic ether .... 


C 4 H 5 0,C l4 H 5 3 


5240 


5409 


4 


Idem. 




C 4 H 5 O,C l0 H 3 O 5 


4878 


4S59 


4 


Malaguti. 


Chloride of acetyl . . . 


C 4 H 3 CI 


2181 


2166 


4 


Liebig & Pelouze. 




C 4 H 3 C1,HC1 


3407 


3443 


4 


Gay-Lus. & Dumas 


Bromide of acetyl . . . 


C 4 H 3 Br 


3642 


3691 


4 


Regnault. 




C 4 H,Br,HBr 


6373 


6485 


4 


Idem. 


Chloral 


C 4 HCI 3 0. 


5060 


5130 


4 


Dumas. 


Chloroform 


C 4 HCI 3 


4116 


4199 


4 


Idem. 


Urethane 


C 6 NH,0 4 


3140 


3096 


4 


Idem. 


Oil of the ardent spirits from 












potatoes 


C| H 1 2 o 2 


3072 


3147 


4 


Idem. 




C 4 H 4 2 


1531 


1532 


4 


Liebig. 


Acetone 


C 6 FI 6 2 


2020 


2019 


4 


Dumas. 


Benzoic acid 


C 14 H 6 4 


4260 


4270 


4 


Dumas & Mitecb. 


Eugenic acid 


C 2 oHj 2 5 


6000 


6400 


4 


Dumas. 


Formomethylal . . . . 


C 6 H 8 4 


2643 


i 2500 


4 


Malaguti. 



ISOMORPHISM. 115 

From these tables, it appears that a simple relation always subsists between 
the combining measures of different bodies in the gaseous state : 

That the combining measure of a few bodies is the same as that of oxygen, 
or one volume ; of a large number, double that of oxygen, or two volumes ; and 
of a still larger number, four times that of oxygen, or four volumes ; while com- 
bining measures of other numbers of volumes, such as three and six, or of 
fractional portions of one volume, such as one-third, are comparatively rare; 

That the specific gravity of a gas may be calculated from its atomic weight, 
or the atomic weight from the specific gravity, as they are necessarily related to 
each other. Thus, to find the specific gravity of a vapour like that of phosphorus, 
of which the combining measure is one volume, or the same as that of oxygen, 
The specific gravities of two bodies, of which the volumes of the atoms are the same, 
must obviously be as the weights of these atoms. Hence, 100 and 392.28 being 
the atomic weights of oxygen and phosphorus, and 1102.6, the known specific 
gravity of oxygen, the specific gravity of phosphorus vapour is obtained by the 
following proportion — 

100 : 392.28 : : : 1102.6 : 4325.28 
= sp. gr. of phosphorus vapour. 

Secondly, to find the specific gravity of a vapour like that of fluorine, of 
which the combining measure may be presumed to be two, or double that of 
oxygen. The atomic weight of fluorine being 233.8, 

100:233.8 :: 1102.6:2578 = 
twice the specific gravity of fluorine, being the weight of two volumes, and the 
specific gravity required is 1289. 

These cases are examples of a general rule, that the specific gravity of a body 
in the state of vapour is obtained by multiplying the atomic weight of the body 
by 1102.6, the specific gravity of oxygen, and divided by 100. The number 
thus found must then be divided by the number of volumes which are known to 
compose the combining measure of the vapour. 

The specific gravities thus calculated are generally more accurate than those 
obtained by direct experiment, from the circumstance that the operation of taking 
the specific gravity of a gas is generally less susceptible of precision, than the 
chemical analyses on which the atomic weights are founded. The densities of 
vapours, taken a few degrees above their condensing points, are generally a 
little greater than the truth, owing to a peculiarity in their physical constitution 
which was formerly explained (page 69.) Of such bodies, therefore, the theo- 
retical is a necessary check upon the experimental density. Indeed, the calcu- 
lated should in all cases be considered and used as the true density. 

RELATION BETWEEN THE CRYSTALLINE FORM AND ATOMIC 
CONSTITUTION OF BODIES— DOCTRINE OF ISOMORPHISM. 

Bodies on passing from the gaseous or liquid to the solid state, generally pre- 
sent themselves in crystals, or regular geometrical figures, which are the larger 
and more distinct, the more slowly and gradually they are produced. Their 
formation is readily observed in the spontaneous evaporation of a solution of sea- 
salt, or in the slow cooling of a hot and saturated solution of alum, which salts 
assume the forms of the cube and regular octohedron. The crystalline form 
of a body is constant, or subject only to certain geometrical modifications which 
can be calculated, and is more serviceable as a physical character for distin- 
guishing salts and minerals. Between bodies of similar atomic constitution, a 
relation in form has been observed of great interest and beauty, which now 
forms a fundamental doctrine of physical science, like the subject of atomic 
weights and volumes just considered. 



116 ISOMORPHISM. 

Gay-Lussac first made the remark that a crystal of potash-alum transferred 
to a solution of ammonia-alum, continued to increase without its form being 
modified, and might thus be covered with alternate layers of the two alums, 
preserving its regularity and proper crystalline figure. M. Beudant afterwards 
observed that other bodies, such as the sulphates of iron and copper, might pre- 
sent themselves in crystals of the same form and angles, although the form was 
not a simple one like that of alum. But M. Mitscherlich first recognised this cor- 
respondence in a sufficient number of cases, to prove that it was a general conse- 
quence of similarity of composition in different bodies. To the relation in form he 
applied the term isomorphism (from to-or, equal, and fttpQv, shape,) and distinguish- 
ed bodies which assume the same figure as isormorphous, or (in the same sense) 
as similiform bodies. The law at which he arrived is as follows: — The same 
number of atoms combined in the same way produce the same crystalline form ; 
and crystalline form is independent of the chemical nature of the atoms, and de- 
termined only by their number and relative position. 

This law has not been established in all its generality, but perhaps no fact 
is certainly known which is inconsistent with it, while an indisposition which 
certain classes of elements have to form compounds at ail similar in composi- 
tion to those formed by other classes, limits the cases for comparison, and 
makes it impossible to trace the law, throughout the whole range of the ele- 
ments, in the present state of our knowledge respecting them. 

The relation of isomorphism is most frequently observed between salts, 
from their superior aptitude to form good crystals. Thus the arseniate and 
phosphate of soda are obtained in the same form, and are exactly alike in com- 
position, each salt containing one proportion of acid, two of soda and one of 
water as bases, together with twenty-four atoms of water of crystallization. With 
a different proportion of water of crystallization, namely, with fourteen atoms, 
and the other constituents unchanged, the crystalline form is totally different, 
but is again the same in both salts. For every arseniate, there is a phosphate 
corresponding in composition and identical in form; the isomorphism of these 
two classes of salts, is indeed perfect. The arsenic and phosphoric acids, 
contain each five proportions of oxygen to one of arsenic and phosphorus re- 
spectively, and are supposed to be themselves isomorphous, although the fact 
cannot be demonstrated, as the acids do not crystallize. The elements, phos- 
phorus and arsenic, are also presumed to be isomorphous: and the ismorphism 
of their acids and salts is referred to the isomorphism of the elements them- 
selves; isomorphous compounds in general appearing to arise from isomor- 
phous elements uniting in the same manner with the same substance. The 
isomorphism of the sulphate, seleniate, chromate and manganate of the same 
base is likewise always clear and easily observed; each of the acids in these cases 
containing three proportions of oxygen to one of selenium, sulphur, chromium 
and manganese, themselves presumed to be isomorphous. Of bases, the iso- 
morphism of the class consisting of magnesia, oxide of zinc, oxide of cadmium 
and the protoxides of nickel, iron and cobalt, is well marked in the salts which 
they form with a common acid, and is particularly observable in the double 
salts of these oxides, such as the sulphate of magnesia and potash, sulphate 
of zinc and potash, sulphate of copper and potash, which have all six atoms 
of water and a common form. The sulphates themselves of these bases differ, 
most of them affecting seven atoms of water of crystallization, while the sul- 
phate of copper affects five; but those with the seven may likewise be crystal- 
lized in favourable circumstances with five atoms of water, and then all assume 
the form of the copper salt, thus exhibiting a second isomorphism like the 
arseniate and phosphate of soda. 

The peroxides of the same class of metals with alumina and the oxide of 
chromium, which consist of two atoms of metal and three of oxygen, also 



ISOMORPHISM. 117 

afford an instructive example of isomorphism, particularly in their double salts. 
The sulphate of the peroxide of iron with sulphate of potash and twenty-four 
atoms of water, forms a double salt having the octohedral form of sulphate of 
alumina and potash or common alum, the same astringent taste, with other 
physical and chemical properties so similar, that the two salts can with diffi- 
culty be distinguished from each other. The salt is called iron-alum, and there 
are corresponding manganese and chrome alums, neither of which contains 
alumina, but the deutoxide of manganese and oxide of chromium in its place, 
with the proportions of acid and water, which exist in common alum. In all 
these salts another substitution may occur without change of form; namely that 
of soda or oxide of ammonium for the potash in the sulphate of potash, giving 
rise to the formation of what are called soda-alum and ammonia alum. 

Certain facts have been supposed to militate against the principles of iso- 
morphism, which require consideration. 

1°. It appears that the corresponding angles of crystals reputed isomorphous 
are not always exactly equal, but are sometimes found to differ one or two 
degrees, although the errors of observation in good crystals rarely exceed 10' 
or 20' of a degree. But it has been shown by Mitseherlich that a difference 
may exist between the inclinations of two series of similar faces in different 
specimens of the same salt, of 59'; while it is also known that the angles of a 
crystal alter sensibly in their relative dimensions with a change of temperature 
(page 26.) The angles of crystals are, therefore, affected in their values 
within small limits by causes of an accidental character, and absolute identity 
in crystalline form may require the concurrence of circumstances which are 
not found together in the ordinary modes of producing many crystals, which 
are still truly ismorphous. 

2°. It appears that the same body may assume in different circumstances, 
two forms which are totally dissimilar and have no relation to each other. 
Thus sulphur on crystallizing from solution in the bisulphuret of carbon or 
in oil of turpentine, at a temperature under 100°, forms octohedrons with 
rhombic bases, but when melted by itself and allowed to cool slowly, it as- 
sumes the form of an oblique rhombic prism on solidifying at 232°. These 
are incompatible crystalline forms, as they cannot be derived from one com- 
mon form. Carbon occurs in the diamond in regular octohedrons, and in 
graphite or plumbago in six-sided plates, forms which are likewise incompa- 
tible. Sulphur and charcoal have each, therefore, two crystalline forms, and 
are said to be dimorphous, (from <$V, twice, and f*op<p», shape.) Carbonate of 
lime is another familiar instance of dimorphism, forming two mineral species, 
calc-spar and arragonite, which are identical in composition, but differ en- 
tirely in crystalline form. G. Rose has lately shown that the first or second 
of these forms may be given to the granular carbonate of lime formed artifi- 
cially, according as it is precipitated at^he temperature of the air, or near the 
boiling point of water. Of its two forms, carbonate of lime most frequently 
affects that of calc-spar; but carbonate of lead which assumes the same two 
forms, and is therefore doubly isomorphous with carbonate of lime, chiefly 
affects that of arragonite, and is very rarely found in the other form. Had 
these carbonates therefore, been each known only in its common form, their 
isomorphism would not have been suspected, an important observation, as the 
want of isomorphism between certain other bodies may be caused by their 
being really dimorphous, although the two forms have not yet been perceived. 
There is no physical impossibility in a body's assuming three different forms, 
or being /n-morphous as well as dimorphous, but no case of trimorphism has 
hitherto been observed. 

3°. The observation of the isomorphism of bodies is of the greatest value as 
an indication that they possess a similar constitution, and contain a like num- 



118 



ISOMORPHISM. 



ber of atoms of their constituents. But it must be admitted that the most 
perfect coincidence in form, or true isomorphism is likewise observed between 
certain bodies which are quite different in composition. Thus bisulphate of 
potash is dimorphous, and crystallizes in one of the two forms of sulphur 
(Mitscherlich.) Nitrate of potash in common nitre has the form of arragonite, 
and occurs also, there is reason to believe, in microscopic crystals in the form 
of calc-spar. Nitrate of soda, again, has the form of calc-spar. Hy perman- 
ganate of barytes and the anhydrous sulphate of soda likewise crystallize in 
one form. Between the first pair, sulphur and bisulphate of potash, the ab- 
sence of all analogy in composition is sufficiently obvious, notwithstanding 
their isomorphism. Between nitrate of potash and carbonate of lime, and be- 
tween hypermanganate of barytes and sulphate of soda, there is no similarity 
of composition, on the ordinary view which is taken of the constitution of 
these salts, but both of these pairs have been assimilated, in speculative views 
of their constitution proposed by Mr. Johnston* in regard to the first pair, and 
by Dr. Clarkt in regard to the second, which merit consideration, although the 
hypotheses cannot possibly be both correct, as they are based upon incompa- 
tible data. Besides these examples of identity of crystalline form without 
any well established relation in composition, many others might be quoted, if 
occurrence in the simple forms of the cube and regular octohedron should be 
allowed to constitute isomorphism. For example: carbon, sea-salt, arsenious 
acid and alum, all occur in octohedrons, although they are no way related in 
composition. But these simple forms are so common, that they can be held 
as affording no proof of isomorphism, unless in cases where it is to be ex- 
pected from admitted similarity of composition, as between the different 
alums, or between chrome iron and octohedral iron ore. 

But notwithstanding the occurrence of such apparently fortuitous coinci- 
dences in form, isomorphism must still be considered as the surest criterion of 
similarity of composition which we possess. Truly isomorphous bodies gene- 
rally correspond in a variety of other properties besides external form. Ar- 
senic and phosphorus resemble each other remarkably in odour, although 
the one is a metal and the other a non-metallic body, while the corresponding 
arseniates and phosphates agree in taste, in solubility, in the degree of force 
with which they retain water of crystallization, and in various other proper- 
ties. The seleniate and sulphate of soda, which are isomorphous, are both 
efflorescent salts, and correspond in solubility, even so far as to agree in an 
unwonted deviation from the usually observed increasing rate of solubility at 
high temperatures, both salts being more soluble in water at 100° than at 212°. 
In fact, isomorphism appears to be always accompanied by many common 
properties, and to be the feature which indicates the closest relationship be- 
tween bodies. 

It will afterwards appear that the more nearly bodies agree in composition, 
they are the more likely to act as solvents of each other, or to be miscible in the 
liquid form. An attraction for each other of the same character is probably the 
cause of the easy blending together of the particles of isomorphous bodies, and 
of the difficulty of separating them after they are once dissolved in a common 
menstruum ; such isomorphous salts as the hypermanganate and hyperchlorate 
of potash, may, indeed, crystallize apart from the same solution, owing to a con- 
siderable difference of solubility ; and potash-alum may be purified, in a great 
measure, by crystallization, from iron-alum, which is more soluble and remains 
in the mother-liquor ; but most isomorphous salts, such as the sulphates of iron 
and copper, when once dissolved together, do not crystallize apart, but compose 

homogeneous crystals, which are mixtures of the two salts in indefinite propor- 

\ 

* Philosophical Magazine, third series, vol. 12, page 480. 
t Records of General Science, vol. iv, page 45. 



CLASSIFICATION OF ELEMENTS. 119 

tions. This intermixture of isomorphous compounds is of frequent occurrence 
in minerals, and was quite inexplicable and appeared to militate against the doc- 
trine of combination in definite proportions, till the power of isomorphous bodies 
to replace each other in compounds was recognised as a law of nature. Thus 
in garnet, which is a silicate of alumina and lime (Al Al Si 3 4 3 Ca Si 3 ) the alu- 
mina is found often wholly or in part replaced by an equivalent quantity of per* 
oxide of iron; while the lime at the same time may be exchanged for protoxide 
of iron or for magnesia, without the proper crystalline character of the mineral 
being destroyed. 

The extent to which the isomorphous relations of bodies have been traced, 
will appear on reviewing the groups or natural families in which the elements 
may be arranged, and observing the links by which the different groups them- 
selves are connected ; these classes not being abruptly separated, but shading 
into each other in their characters, like the classes created by the naturalist for 
the objects of the organic world. 

CLASSIFICATION OF ELEMENTS. 

The First class comprises four elementary bodies : oxygen, sulphur, selenium, 
tellurium. The last three of these elements exhibit the closest parallelism in 
their own properties, in the range of their affinities for other bodies, and in the 
properties of their analogous compounds. They all form gases with one atom 
of hydrogen, and powerful acids with three atoms of oxygen, of which the salts, 
the sulphates, seleniates and tellurates are isomorphous; and the same relation 
undoubtedly holds in all the corresponding compounds of these elements. 

Oxygen has not yet been connected with this group by a certain isomorphism 
of any of its compounds, but a close correspondence between it and sulphur ap- 
pears, in their compounds with one class of metals being alkaline bases of simi- 
lar properties, forming the two great classes of oxygen and sulphur bases, such 
as oxide of potassium andsulphuret of potassium; and in their compounds with 
another class of elements being similar acids, giving rise to the great classes of 
oxygen and sulphur acids, such as arsenious and sulfarsenious acids. They far- 
ther agree in the analogy of their compounds with hydrogen, particularly of per- 
oxide of hydrogen and persulphuret of hydrogen, both of which bleach and are 
remarkable for their instability ; and in the analogy of alcohol and mercaptan, 
which last may be considered as an alcohol with its oxygen replaced by sulphur. 
This class is connected with the next by manganese, of which manganic acid is 
isomorphous with sulphuric acid, and consequently manganese with sulphur. 

Second Class. — This class comprises magnesium, calcium, manganese, iron, 
cobalt, nickel, zinc, cadmium, copper, hydrogen, bismuth, chromium, aluminum, 
glucinum, vanadium, zirconium, yttrium, thorinum. The protoxides of this class, 
including water, form analogous salts with acids. A hydrated acid, such as 
crystallized oxalic acid or the oxalate of water, corresponding with the oxalate 
of magnesia; hydrated sulphuric acid (HO, SO,-fHO) with the sulphate of mag- 
nesia (MgO, SO 3 -f HO.) The isomorphism of the salts of magnesia, zinc, cad- 
mium and the protoxides of manganese, iron, nickel and cobalt is perfect. But 
water has not been shown to be isomorphous with these oxides, although it 
greatly resembles oxide of copper in its chemical relations. Lime is not so 
closely related as the other protoxides of this group, being allied to the following 
class. But its carbonate, both anhydrous and hydrated, its nitrate and the chlo- 
ride of calcium assimilate with the corresponding compounds of the group ; while 
to its sulphate or gypsum, CaO, S0 3 + 2HO, one parallel and isomorphous com- 
. pound, at least, can be adduced, a sulphate of iron, FeO, S0 3 -f 2HO (Mitscher- 
lich,) which is also sparingly soluble in water like gypsum. 



120 ISOMORPHISM. 

Bismuth is placed in this class from its nitrate and subnitrate, which are strictly 
analogous in composition to the nitrate and sub-nitrate of copper, but their iso- 
morphism has not been observed. The salts of the oxide of chromium, of alu- 
mina and glucina are isomorphous with those of peroxide of iron (Fe 2 3 ,) with 
which these oxides correspond ; and the salts of manganic and chromic acids 
are isomorphous, and agree with the sulphates. The vanadiates are believed to 
be insomorphous with the chromates. Zirconium is placed in this class, because 
its fluoride is isomorphous with that of aluminum and that of iron, and its oxide 
appears to have the same constitution as alumina ; and yttrium and thorium 
solely because their oxides, supposed to be protoxides, are classed among the 
earths. 

Third class. — Barium, strantjum, lead. The salts of their protoxides, barytes, 
strontian, and oxide of lead are strictly isomorphous, and one of them, at least, 
oxide of lead is dismorphous, and assumes the form of lime, and the preceding 
class in the mineral plumbocalcite (Johnston.) But certain carbonates of the 
second class are dimorphous, and enter into the present class, as the carbonate 
of lime in arragonite, carbonate of iron in junckerite, and carbonate of magne- 
sia procured by evaporating its solution in carbonic acid water to dryness by 
the water-bath (G. Rose,) which have all the common form of carbonate of 
strontian. Indeed these two classes are very closely related. 

The fourth class consists of potassium, ammonium, sodium, silver. The term 
ammonium is applied to a hypothetic compound of one atom of nitrogen and 
four of hydrogen (NH 4 ), which is, therefore, certainly not an elementary body, 
and probably not even a metal, but which is conveniently assimilated in name to 
potassium, as these two bodies occupy the same place in the two great classes 
of potash and ammonia salts, between which there is the most complete isomor- 
phism. Potassium and ammonium themselves are, therefore, isomorphous. The 
sulphates of soda and silver are similiform, and hence also the metals sodium 
and silver ; but their isomorphism with the preceding pair is not so clearly es- 
tablished. Soda replaces potash in soda-alum, but the form of the crystal is the 
common regular octohedron ; nitrate of potash has also been observed in mi- 
croscopic crystals having the arrogonitic form of nitrate of soda,* which is better 
evidence of isomorphism, although not beyond cavil as the crystals were not 
measured. There are also grounds for believing that potash replaces soda in 
equivalent quantities in the mineral chabasie, without change of form. The 
probable conclusion is that potash and soda are insomorphous, but that this re- 
lation is concealed by dimorphism, except in a very few of their salts. 

This class is connected in an interesting way with the other classes through 
the second. The sub-sulphuret of copper and the sulphuret of silver appear to 
be insomorphous, although two atoms of copper are combined in the one sulphu- 
ret and one atom of silver in the other, with one atom of sulphur; their formu- 
lae being — 

Cu 2 S and Ag S. 
Are then two atoms of copper insomorphous with one atom of silver? In the 
present state of our knowledge of isomorphism, it will be wise to admit that 
they are. 

The fourth class will thus stand apart from the second which is represented 
by copper, and also from the other classes connected with the second, in so far 
as one atom of the present class is equivalent to two atoms of the other classes 
in the production of the same crystalline form. This discrepancy may be at 
once removed by halving the atomic weight of silver, and thus making both sul- 

* Frankenheim in PaggendorfPs Annalen, vol. 40, page 447. See also a paper by Pro. . 
fessor Johnston on the received equivalents of potash, soda and silver ; Phil. Mag. third 
series, vol. 12, page 324. 



CLASSIFICATION OF ELEMENTS. 121 

phurets to contain two atoms of metal to one of sulphur (Johnston ubi supra.) 
But the division of the equivalents of sodium, potassium and ammonium which 
would follow that of silver, and the consideration of potash and soda as subox- 
ides are most violent assumptions, and not to be lightly entertained. 

It has been inferred that lime with an atom of water is probably isomorphous 
with potash and soda, because CaO-f HO appears to replace KO or NaO in 
mesotype, chabasie and other minerals of the zeolite family. 

Fifth Class. — Chlorine, iodine, bromine, fluorine. These four elements 
form a well defined natural family. The first three are isomorphous through- 
out their whole combinations, chlorides with iodides, chlorates with iodates, 
hyperchlorates with hyperioclates, &c; and such fluorides also as can be com- 
pared with chlorides appear to affect the same forms. It is connected with 
the second class through hyperchloric acid; the hyperchlorates being strictly 
isomorphous with the hy permanganates. But the formulae of these two acids 
are — 

C10 7 and Mn 2 7 , 
one atom of chlorine replacing two atoms of manganese. Or, this class has 
the same isomorphous relation as the preceding class to the others. And such 
I shall assume to be its true relation, although halving the atomic weight of 
chlorine, which would give two atoms of chlorine to hyperchloric acid, is not 
so improbable a supposition as dividing that of sodium; still it would lead to 
the strange conclusion that chlorine enters into its other compounds, as well 
as into hypermanganic acid, always in the proportion of two atoms; for that 
element is never known to combine in a less proportion than is expressed by 
its presently received equivalent. It appears that a salt has been casually ob- 
served to occur in the preparation of hypermanganate of potash having exactly 
the figure of chlorate potash, and containing a corresponding acid of manganese 
in which two of metal still represent one of chlorine as in hypermanganic 
acid.* 

Sixth class. — Nitrogen, phosphorus, arsenic, antimony; also composing a 
well marked natural group, of which nitrogen and antimony are the two ex- 
tremes, and of which the analogous compounds exhibit isomorphism. These 
four elements all form gaseous compounds with three atoms of hydrogen, 
namely, ammonia, phosphuretted, arseniuretted and antimoniuretted hydrogen. 
The hydriodates of ammonia and of phosphuretted hydrogen are also isomor- 
phous; so are arsenious acid and the oxide of antimony, both of which contain 
three atoms of oxygen to one of metal. Arsenious acid also is capable of re- 
placing oxide of antimony in tartrate of antimony and potash or tartar emetic, 
without change of form, and arsenic often substitutes antimony in its native 
sulphuret. The nitrous acid (N0 3 ) which corresponds with arsenious acid 
and oxide of antimony, likewise acts occasionally as a base, as in the crystal- 
line compound with sulphuric acid of the leaden chambers used in the manu- 
facture of the latter acid. The complete isomorphism of the arseniates and 
phosphates has already been noticed. But phosphoric acid forms two other 
classes of salts, the pyrophosphates and metaphosphates, to which arsenic acid 
supplies no parallels. At present this class of elements can be connected by 
means of an isomorphous link with no other. It approaches most nearly to 
the fifth class, nitrogen and chlorine both forming a powerful acid with five 
proportions of oxygen, nitric acid and chloric acid; but of the many nitrates and 
chlorates which can be compared, no two have proved isomorphous. Nor 
do the metaphosphates appear at all like the nitrates, although their formulae 
correspond. 

Seventh class. — Tin, titanium. Connected by the isomorphism of titanic 

* Liebig's Introduction to the First Elements of Chemistry, by Richardson, page 87. 
11 



122 



ISOMORPHISM. 



acid and peroxide of tin (Ti0 2 and Sn0 2 .) Titanium is connected in a 
curious manner with iron and the second class. Titanic acid occurs in ilme- 
nite and other varieties of titanic iron, in combination with protoxide of iron, 
and in the crystalline form of the peroxide of that metal; namely, that of spe- 
cular iron, and also of corundum (alumina.) Hence, 
Fe,0 3 , or (Fe+Fe)-f0 3 , and 
FeO-f Ti0 2 , or (Fe-f Ti)-f 3 
are isomorphous. Now it is to be remarked that peroxide of iron and titaniate 
of iron, although they agree in the number of their elements, each containing 
three of oxygen and two of metal, are yet not certainly analogous in proximate 
composition. If an acid of iron, consisting, like titanic acid, of one of metal 
and two of oxygen-were known, which might be called ferric acid, then spe- 
cular iron would be a ferrate of the protoxide of iron, as the other is a titaniate 
of the same base, and their isomorphism would be intelligible, and present 
nothing unusual. But if ferric acid does not exist, and it has hitherto eluded 
research,* then the isomorphism of the bodies in question seems to imply that 
this relation does not require similarity of constitution but merely equality in 
the number of atoms contained in the bodies which exhibit it. 

Eighth Class. — Silver and gold. From their isomorphism in the metallic 
state. Gold will thus be connected, through silver, with sodium and the fourth 
class. 

Ninth Class. — Platinum, palladium, iridium, osmium. From the isomor- 
phism of their double chlorides. The bichloride of tin with chloride of po- 
tassium crystallizes in regular octohedrons, like the double bichloride of plati- 
num and potassium, and other double chlorides of this group; which although 
not alone sufficient to establish an isomorphous relation between this class and 
the seventh, yet favours the notion of its existence (Dr. Clark.) 

Tenth Class. — Tungsten and molybdenum. From the isomorphism of the 
tungstates and molybdates, the salts of tungstic and molybdic acids, W0 3 
and MoO 3 . Mr. Johnston has observed that the chromate of lead is dimor- 
phous, and corresponds in the least usual of its forms with the molybdate of 
lead. This establishes a relation between molybdic, chromic, sulphuric and 
other analogous acids.t 

Eleventh Class. — Carbon, boron, silicon. These elements are placed toge- 
ther from a general resemblance which they exhibit without any precise rela- 
tion. They are not known to be isomorphous among themselves, or with any 
other element. They are non-metallic, and form weak acids with oxygen, — 
the carbonic, consisting of two of oxygen and one of carbon, and the boracic 
and silicic acids, which are generally viewed as composed of three of oxygen 
to one of boron and silicon. Silicic acid may, perhaps, replace alumina in 
some minerals, but this is uncertain. 

Of the elements which have not been classed, no isomorphous relations are 
known. They are mercury, which in some of its chemical properties is ana- 
logous to silver, and in others to copper, cerium, columbium, lithium, rhodium 
and uranium. 

According to the original law of Mitscherlich, that isomorphism depends 
upon equality in the number of atoms, and similarity in their arrangement, 
without reference to their nature, the elements themselves should all be iso- 
morphous. Most of the metals crystallize in the simple forms of the cube or 
regular octohedron, which are not sufficient to establish this relation. But the 

* [The existence of ferric acid has been rendered evident since the above observations 
were published, Fremy having obtained iron in a higher state of oxidation and combined 
with potassa, by chemical means. (Ann. of Elect, and Galv. Aug. 1842,) and Poggendorf, 
by the agency of Galvanism. (Ann. der Phys. und Chim.) R. B.] 

t Phil. Mag. third series, vol. 12, p. 387. 



CLASSIFICATION OF ELEMENTS. 123 

isomorphism of a large proportion, if not the whole, of the elements may be 
inferred from the isomorphism of their analogous compounds. Thus from the 
facts just adduced, it appears that the members of the following large class of 
elements are linked together from the isomorphism of one or more of their 
compounds. This large class may be subdivided into smaller classes, between 
the members of which, isomorphism is of more frequent occurrence, and 
which are then to be viewed as isoraorphous groups. 

ISOMORPHOUS ELEMENTS. 

1. Sulphur 3. Barium 

Selenium Strontium 

Tellurium Lead 



. Magnesium 


4. Tin 


Calcium 
Manganese 


Titanium 




Iron 


5. Tungsten 


Cobalt 


Molybdenum 


Nickel 
Zinc 






Cadmium 


• With two atoms of the preceding 


Copper 


elements. 


Chromium 


6. Sodium 


Aluminum 


Silver 


Glucinum 


Gold 


Vanadium 


Potassium 


Zirconium 


Ammonium 



7. Chlorine 
Iodine 
Bromine 
■» Fluorine 

The only known group of isomorphous elements which cannot be connected 
in a probable manner with the above large class, is that of 

Nitrogen Arsenic 

Phosphorus Antimony. 

The tendency of discovery is to bring all the elements into one class, either 
as isomorphous atom to atom, or with the relation to the others which chlo- 
rine and sodium exhibit. 

But must not isomorphism be implicitly relied upon in estimating atomic 
weights, and the alterations which it suggests be adopted without hesitation 
in every case? Chemists have always been most anxious to possess a simple 
physical character by which atoms might be recognised; and equality of vo- 
lume in the gaseous state, equality of specific heat, and similarity in crystal- 
line form have all in their turn been upheld as affording a certain criterion. 
The indications of isomorphism certainly accord much better than those of the 
other two criteria with views of the constitution of bodies derived from con- 
siderations purely chemical, and are indeed invaluable in establishing analogy 
of composition in a class of bodies, by supplying a precise character which can 
be expressed in numbers, instead of that general and ill-defined resemblance 
between allied bodies, which chemists perceived by an acquired tact rather 
than by any rule, and which was heretofore their only guide in classification, 



124 



DIMORPHISM. 



Admitting that isomorphism is a certain proof of similarity of atomic constitu- 
tion within a class of elements and their compounds, it may still be doubted 
whether the relation of the atom to crystalline form is the same without mo- 
dification throughout the whole series of the elements, or whether all atoms 
agree exactly in this or any other physical character. 

Crystalline form and the isomorphous relation may prove not to be a reflec- 
tion of atomic constitution, or immediately and necessarily connected with it, 
but to arise from some secondary property of bodies, such as their relation to 
heat: in which a simple atom may occasionally resemble a compound body, 
as we find sulphur isomorphous in one of its forms, with bisulphate of potash. 
While we find another simple atom, potassium, isomorphous through a long 
series of compounds with the group of five atoms- which constitute ammonium. 
The occurrence of dimorphism also both in simple and compound bodies gives 
to crystalline form a secondary character. 

Is it probable that sulphur and carbonate of lime could be made to appear 
in sets of crystals which are wholly unlike, merely by a slight change of 
temperature, if form were the consequence of an invariable and atomic consti- 
tution? Crystalline form then may possibly depend upon some at present un- 
known property of bodies, which may have a frequent and general, but cer- 
tainly not an invariable relation to their atomic constitution. There may be 
nothing truly inconsistent with the principles of isomorphism in one atom of 
a certain class of elements having the same crystallographic value as two 
atoms of another class, the relation which has been assumed to exist between 
the sodium and chlorine classes and the others, particularly when the classes 
stand apart, and differ in their properties from all the others, as those of so- 
dium and chlorine do. 

The atomic weight of hydrogen ought not to be divided or reduced from 
12.5 to 6.25, for that element certainly belongs to the natural family of mag- 
nesium or the second class, of which the equivalents must remain fixed, as 
they are practically the standards of comparison for all others. If hydrogen 
be divided, so must magnesium, calcium, manganese and the whole class. 
But it has at last been admitted that hydrogen never combines in a less pro- 
portion than 12.5, and the indivisibility of its equivalent therefore conceded;* al- 
though it is proposed to make a distinction between the values of the equiva- 
lent and of the atom of a body which is altogether uncalled for. 



DIMORPHISM. 

Many solid bodies admit of a variation of properties while in that state of 
which gases and liquids are not susceptible. The assumption of two incompa- 
tible crystalline forms by the same body, in different circumstances, has already 
been noticed as occurring with sulphur, carbon, carbonates of lime and lead, 
bisulphate of potash and chromate of lead. It is also observed, in the biphos- 
phate of soda, and in a considerable number of minerals. The dimorphous 
crystals may differ in density, the densities of calc-spar and arragonite, the 
forms of carbonate of lime, being 2.719 and 2.949, and indeed all resemblance 
in properties between the crystals may be lost, as in diamond and graphite, 
the two forms of carbon. The particular form assumed by sulphur and car- 
bonate of lime, which may be made to crystallize in either of their forms at 
will, is found to depend upon the degree of temperature at which the solid is 
produced; carbonate of lime being precipitated, on adding chloride of calcium 
to carbonate of ammonia, in a powder, of which the grains have the form of 
calc-spar or of arragonite, according as the temperature of the solution is 50° 

* By Berzelius, L'Institut, May 1838, page 160. 



CLASSIFICATION OF ELEMENTS. 125 

or 150°.* A large crystal of arragonite when heated by a spirit-lamp, decre- 
pitates and falls into a powder composed of grains of calc-spar. The crystals 
of sulphur produced at the higher of two temperatures, become opaque when 
kept for some days in the air, and pass spontaneously into the other form; 
while the crystals produced at the lower temperature are disintegrated, and 
changed into the other form by a moderate heat. These observations are im- 
portant as establishing a relation between dimorphism and solidification at dif- 
ferent temperatures. 

A considerable variation of properties is likewise often observable in a solid, 
which is not crystalline, or of which the crystalline form is indeterminate. 
Thus sulphuret of mercury obtained by precipitating corrosive sublimate by 
sulphuretted hydrogen, is black ; but the same body when sublimed by heat, 
or produced by agitating mercury in a solution of the persulphuret of potassium, 
form cinnabar, of which the powder is the red pigment vermillion ; while Ver- 
million itself, if heated till sulphur begins to sublime from it, and then suddenly 
thrown into cold water, becomes black ; although if allowed to cool slowly it 
remains red, yet it is of the same composition exactly in the black and red 
states. The iodide of mercury newly sublimed is of a lively yellow colour, and 
may remain so for a long time, but it generally begins to pass into a fine scarlet 
on cooling, and may be made to undergo this change of colour, in an instant, 
by strongly pressing it. The precipitated sulphuret of antimony may be de- 
prived of the water it contains, at the melting point of tin, without losing its pe- 
culiar orange colour ; but when heated a little above that temperature, it shrinks 
and assumes the black colour and metallic lustre of the native sulphuret, with- 
out any loss of weight. Again the black sulphuret when heated strongly and 
thrown into water, loses its metallic lustre, and acquires a good deal of the ap- 
pearance of the precipitated sulphuret. The nitrites are sometimes white and 
sometimes yellow ; and crystals of sulphate of manganese are often deposited 
from the same solution, some of which are pink and others colourless, although 
identical in composition. 

Such differences of colour are permanent, and not to be confounded, with 
changes which are peculiar to certain temperatures : thus oxide of zinc is of a 
lemon yellow colour, when strongly heated, but milk-white at a low tempe- 
rature : the oxide of mercury is much redder, at a high than at a low tempera- 
ture, and bichromate of potash, which is naturally red, becomes almost black 
when fused by heat. Even bodies in the gaseous state are liable to transient 
changes of this kind, the brown nitrous fumes being nearly colourless below 
zero, and on the other hand deepening greatly in colour at a high temperature. 

The condition of glass is a remarkable modification of the solid form assumed 
by many bodies. Matter in this state is not crystallized, and on breaking pre- 
sents curved and not plain surfaces, or its fracture in mineralogical language 
is conchoidal, and not sparry. The indisposition to crystallize, which causes 
solidification in the form of glass, is more remarkable in some bodies, such as 
phosphoric and boracic acids, and their compounds, than in others. The Di- 
phosphate and binarseniate of soda have the closest resemblance in properties, 
yet when both are fused by a lamp, the first solidifies on cooling into a transpa- 
rent colourless glass, and the second into a white opaque mass composed of 
interlaced crystalline fibres. The phosphate at the same time discharges sensibly 
less heat, than the arseniate in solidifying, retaining probably a portion of its heat 
of fluidity or latent heat in a state of combination, while a glass. None of the 
compounds of silicic acid and a single base, or simple silicates, becomes a glass 
on cooling from a state of fusion, with the exception of the silicate of lead con- 



* G.Rose, Phil. Mag., 3d Series, vol. 12, p. 465. 
11* 



126 DIMORPHISM. 

taining a great excess of oxide : they all crystallize. But a mixture of the same 
silicates when fused, exhibits a peculiar viscosity or tenacity, appears to have 
lost the faculty of crystallizing, and constantly forms a glass. The varieties of 
glass in common use are all such mixtures of silicates. Glass is sometimes 
devitrefied when kept soft by heat for a long time, owing to the separation of 
the silicates from each other and their crystallization ; and the less mixed glasses 
are known to be most liable to this change. It is probable that all bodies differ 
when in the vitreous and in the crystalline forms in the proportion of combined 
heat which they possess, as has been observed of melted sugar (page 52) in these 
two conditions. 

Arsenious acid when fused or newly sublimed appears as a transparent glass 
of a light yellow tint. But left to itself, it slowly becomes opaque and milk 
white; the change commencing at the surface and advancing to the centre, and 
often requiring years to complete it in a considerable mass. The arsenious 
acid is no longer vitreous, being changed into a multitude of little crystals, 
whence results its opacity; and it has altered slightly at the same time in den- 
sity and in solubility. But the passage from the vitreous to the crystalline 
state may take place instantaneously, and give rise to an interesting pheno- 
menon lately observed by H. Rose. The vitreous arsenious acid seems to 
dissolve in dilute and boiling hydrochloric acid without change, but the solu- 
tion on cooling deposits crystals which are of the opaque acid, and a flash of 
light, which may be perceived in the dark, is emitted in the formation of each 
crystal. This phenomenon depends upon and indicates the transition, for it 
does not occur when arsenious acid already opaque is substituted for vitreous 
acid, and dissolved and allowed to crystallize in the same manner. 

A still greater change than those described, is induced upon certain bodies 
by exposure to a high temperature, without any corresponding change in their 
composition. Several metallic peroxides, such as alumina, oxide of chromium 
and peroxide of tin cease to be soluble in acids after being heated to redness. 
The same is true of a variety of salts, such as many phosphates, antimoniates 
and silicates. All these bodies contain water in combination, when most 
readily dissolved by acids; which constituent is dissipated at a high tempera- 
ture, but in general before the loss of solubility occurs, so that the contained 
water alone is not the cause of the solubility. Berzelius remarked an ap- 
pearance often observable when such bodies are under the influence of heat, 
and in the act of passing from the soluble to the insoluble state. They sud- 
denly glow or become luminous, rising in temperature above the containing 
vessel, from a discharge of heat. The rare mineral gadolinite affords a beau- 
tiful example of this change. When heated it appears to burn, emits light, 
and becomes yellow, but undergoes no change in weight. Many bodies ex- 
hibit a feeble phosphorescence when heated, which has no relation to this change 
and is to be distinguished from it. 

The circumstance most certain respecting this change in bodies, which af- 
fects so deeply their chemical properties, is that the bodies do not contain a 
quantity of heat, after the change, which they must have possessed before its 
occurrence in a combined or latent form. No ponderable costituent is lost, 
but there is this loss of heat. A change of arrangement of the particles, it is 
true, might occur at the same time in some of these bodies, such as is ob- 
served when sulphite of soda is converted by heat into a mixture of sulphate 
of soda and sulphuret of sodium, without change of weight; but it would be 
difficult to apply an explanation of this nature to oxides, such as alumina 
and peroxide of tin, which contain only two constituents. The loss of heat 
observed will afford all the explanation necessary if heat be admitted as a con- 
stituent of bodies equally essential as their ponderable elements. As the oxide 
of chromium possesses more combined heat when in the soluble than in the 
insoluble state, the first may justly be viewed as the higher caloruret, and the 



ISOMERISM. 127 

body in question may have different proportions of this as well as of any 
other constituent. But it is to be regretted that our knowledge respecting heat as 
a constituent of bodies is extremely limited; the definite proportion in which 
it enters into ice and other solids in melting, and into steam and vapours has 
been studied, and also the proportion emitted during the combustion of many 
bodies, which has likewise proved to be definite. But the influence which its 
addition or subtraction may have on the chemical properties of a body is at 
present entirely matter of conjecture. The phenomena under considera- 
tion seem to require the admission of heat as a true constituent which can mo- 
dify the properties of bodies very considerably, otherwise a great physical law 
must be abandoned, namely, that " no change of properties can occur without 
a change of composition." But if heat be once admitted as a chemical con- 
stituent of bodies, then a solution of the present difficulties may be looked for, 
for nothing is more certain than that " a change in composition will account for 
any change in properties." Heat thus combined in definite proportions with 
bodies and viewed as a constituent, must not be confounded with the specific 
heat of the same bodies or their capacity for sensible heat, which may have no 
relation to their combined heat. 



ISOMERISM. 

In such changes of properties the individuality of the body is never lost. But 
numerous instances have presented themselves of two or more bodies possessing 
the same composition, which are unquestionably different substances and not 
mutually convertible into each other. Different bodies thus agreeing in compo- 
sition but differing in properties are said to be isomeric, (from i<ro$ equal, and 
tugoq, part,) and their relation is termed isomerism. The discovery of such 
bodies excited much interest and they have received of late years a considerable 
share of the attention of chemists. But the result of a careful study of the bodies 
associated by similarity of composition, though differing in properties, has been 
upon the whole unfavourable to the doctrine of isomerism. Isomeric bodies have 
in general been found to agree in the relative proportion of their constituents 
only, and to differ either in the aggregate number of the atoms composing them, 
or in the mode of arrangement of these atoms ; and very few cases of isomerism 
now remain which do not admit of explanation. This is what was to be" expect- 
ed, for isomerism in the abstract is improbable, a difference in properties between 
bodies, without a difference in their composition, appearing to be an effect with- 
out a sufficient cause. Hence, the term isomerism is now generally employed 
in a limited sense, to indicate simply the identity in composition of two or more 
bodies as expressed in the proportion of their constituents in 1 00 parts. Several 
classes of such isomeric bodies may be formed. 

The members of the most numerous class of isomeric bodies differ in atomic 
weight. Thus we know at present three gases, three, or four liquids, and as 
many solids which all consist exactly of carbon and hydrogen in the proportion 
of one atom to one atom, or in weight, of 86 parts of carbon and 14 of hydrogen 
very nearly. These bodies agree in ultimate composition, but differ completely 
in every other respect. But a representation of their chemical constitution ex- 
plains at once the cause of the differences they present, as is obvious in the fol- 
lowing formulae of four of the best characterized members of this isomeric group : 

Equivalents and combining measure. 

Methylene. . . . . C 2 H 2 or 4 volumes. 

Olefiant gas C 4 H 4 or 4 volumes. 

Gas from oil. . . . . C 8 H s or 4 volumes. 

Cetene C 32 H 38 or 4 volumes* 



128 ISOMERISM. 

It thus appears that the atom of cetene contains four times as many atoms of 
carbon and hydrogen as the atom of the gas from oil, eight times as many as the 
atom of defiant gas, and sixteen times as many as the atom of methylene ; while 
as the atom of all these bodies affords the same measure of vapour or four vo- 
lumes, they must differ as much in density as they do in the number of their 
constituent atoms. It is not surprising, therefore, that they all possess different 
and peculiar properties. Several groups of bodies might be selected from Table 
II, at page 1 1 4, which have a similar relation to each other, the number of their 
atoms being different, although their relative proportion is the same, such as : 
Oil of lemons, . . . . C l0 H 8 

Oil of turpentine C 20 H 16 

and, 

Naphthaline. . . . . C 30 H 8 

Paranaphthaline. . . .• . C 30 H l2 
A still more remarkable case is presented to us in alcohol, and the ether from 
wood spirit, in which there is identity of condensation as well as of composition, 
with different equivalents. Their vapours have in fact the same specific gravity, 
and contain under equal volumes, equal quantities of carbon, hydrogen and oxy- 
gen. But we know that each of these bodies is composed of two others, alco- 
hol of one atom of olefiant gas, and two atoms of water; and the ether of wood- 
spirit, of one atom of methylene, and one of water, so that their constitution and 
rational formulae are quite different : 

Alcohol C 4 H 4 4 2tiO 

Ether of wood spirit. . . C 2 H 2 +HO 
In another class of isomeric bodies, the atomic weight may be equal, as well 
as the elementary composition. A pair belonging to this class are known, which 
coincide besides in the specific gravity of their vapours. The composition and 
atom of both formic ether and the acetate of methylene may be represented by 
C 5 H 5 4 ; the density of both their vapours is 2574 ; and what is very remark- 
able, these bodies in their ordinary liquid state almost coincide in properties, the 
density of formic ether being 0.916, and that of the acetate of methylene 0.919, 
(density of water being 1000,) while the first boils at !33°, and the last at 
136.4°. But when acted on by alkalies, their products are entirely different, 
the one affording formic acid and alcohol, and the other acetic acid and wood- 
spirit. Each of the isomeric bodies in question contains, indeed, two different 
binary compounds, and their constitution is truly represented by different for- 
mulae : 

Formic ether C 4 H 5 O-f C 2 H0 3 

Acetate of methylene. . . . C 2 H 3 0fC 4 H 3 3 
in which the same atoms are seen to be very differently arranged, 

The last class of isomeric bodies are of the same atomic weights, but their 
constitution or molecular arrangement being unknown, their isomerism, can- 
not at present be explained. It can scarcely be doubted, however, that their 
molecular arrangement is really different. Cyanic and fulminic* acids are in 
this predicament, their common formula being NC 2 O. Malic and citric 
acids were also believed to present a similar relation, but recent discoveries 
respecting the constitution of their salts have separated these and several other 
acids heretofore viewed as isomeric. 

One pair, however, of isomeric bodies remains which have defeated every 
attempt at explanation, the racemic and tartaric acids, which exhibit a simi- 
larity of properties, and a paralellism in their chemical characters that are 
truly astonishing. These acids are found together in the grape of the upper 

[* Fulminic acid is now considered to have double the atomic weight of cyanic acid. 
See these acids, R. B.] 



ARRANGEMENT OF THE ELEMENTS IN COMPOUNDS. 129 

Rhine. They differ considerably in solubility, the racemic being the least 
soluble, so that they may be separated from each other by crystallization; 
and the racemic acid contains an atom of water of crystallization, which is 
not found in the crystals of tartaric acid. They form salts which correspond 
very closely in their solubility and other properties. The bitartrate and bi- 
racemate of potash are both sparingly soluble salts: the tartrates and racemates 
of lime, lead and barytes are all alike insoluble. Both acids form a double 
salt with soda and ammonia, which is an unusual kind of combination. But 
what is most surprizing, crystals of these double salts, not only coincide in 
the proportion of their water and other constituents and in the composition of 
their acids but also in external form, having been observed by Mitscherlich 
to be isomorphous. A nearer approach to identity could scarcely be con- 
ceived than is exhibited by these bodies, which are, indeed, the same both in 
form and composition. The crystallized acids are both modified in an un- 
usual manner by heat, and form three classes of salts, as phosphoric acid does. 
The formula of both acids in their ordinary class of salts is C 8 H 4 O l0 + 
two atoms of base (Fremy.) But by no treatment can the one acid be trans- 
muted into the other. Lastly, every organic acid produces a new acid by de- 
structive distillation, which is peculiar to it and is termed its pyr-acid. Now 
racemic and tartaric acid, when destroyed by heat, agree in giving birth to one 
and the same pyr-acid.* 



ARRANGEMENT OF THE ELEMENTS IN COMPOUNDS. 

The names of some compounds imply that they contain other compounds, 
and indicate a certain atomic constitution, while the names of other compounds 
express no particular airang-cuient of their constituent atoms, but leave it to be 
inferred that the atoms are all directly combined together. Thus sulphate of 
soda implies the continued existence of sulphuric acid and soda in the salt, 
while nitric acid or peroxide of hydrogen, supposes no partition of the com- 
pound to which it is applied. But it is to be remembered that the original 
framers of the nomenclature were guided more by facilities of an etymological 
nature in constructing such terms, than by views of the constitution of com- 
pounds. 

Of a binary compound containing single atoms of its constituents, there can- 
not be two modes of representing the constitution, but where one of the con- 
stituents, is present in the proportion of two or more atoms, several hypothe- 
ses can always be formed of their mode of aggregation. In a series of binary 
combinations of the same elements, such as that of nitrogen and oxygen, 
NO j, N0 2 , N0 3 , N0 4 , N0 5 , the simplest view has generally been taken, 
namely that it is the elements themselves which unite. But in particular 
cases the chemist is often involuntarily led into another opinion. Thus deu- 
toxide of nitrogen is so often a product of the decomposition of nitric acid, 
that it appears more like a compound of that oxide of nitrogen with oxygen, 
than a compound of nitrogen itself with oxygen. When the peroxide of hy- 
drogen was first discovered by Thenard, he was led by the whole train of its 
properties to view it as a compound of water and oxygen, into which it is re- 
solved with so much facility, and to name it accordingly oxygenated water, 
which it may be, and not a direct combination of hydrogen and oxygen: or 
its formula may be HO + 0, and not H0 2 . The periodide of potassium and 
the other analogous compounds obtained by dissolving iodine in metallic 

[* The apparent isomerism of these acids is accounted for under the head of Paratar- 
taric acid. R. B,] 



130 ARRANGEMENT OF THE ELEMENTS IN COMPOUNDS. 

iodides, were first termed ioduretted iodides from similar considerations, and 
the hyposulphites, obtained by dissolving sulphur in sulphites, sulphuretted 
sulphites. It may be doubted whether chemists would return with advantage 
to any of these expressions, the views of composition which they indicate be- 
ing uncertain, and not offering a sufficient inducement to depart from the more 
systematic designations. The peroxide of hydrogen, for instance, may be 
easily resolved into water and oxygen, not because water pre-exists in it, but 
because water is a compound of great stability and is formed when peroxide 
of hydrogen is decomposed. Nitric acid, also, is as likely to be a. compound 
of peroxide of nitrogen with an additional atom of oxygen, as of deutoxide of 
nitrogen, with three atoms of the same element. 

Certain compound bodies, however, have been observed to act the part of 
a simple body in combination, and can be traced through a series of com- 
pounds. The following substances, for instance, may be represented with 
considerable probability as compounds of carbonic oxide, as in the formulae. 
CO, carbonic oxide 

CO ■+• 0, carbonic acid. 
CO+C1, chloroxicarbonic acid. 
2CO+0, oxalic acid. 
2CO + CI, chloroxalic acid. 
Carbonic oxide is said to be the radical of this series, a name applied to any 
compound which is capable of combining with simple bodies, as carbonic 
oxide appears to do with oxygen and chlorine in these compounds. Messrs. 
Liebig and Wdhler have shown by decisive experiments that such a radical 
exists in the benzoic combinations, which may be represented thus: 

C 14 HjOj+O, benzoic acid. 

C 14 H 5 2 -f- H, essential oil of almonds. 

C 14 H 5 2 + Ol, chloride of benzoyl*, etc. 
Cyanogen wae the first recognised member of the class of compound radicals, 
of which the number known to chemists is constantly increasing, and which 
appear to pervade the whole compounds of organic chemistry, fn combining 
with simple bodies, radicals act the part of other simple bodies, such as metals, 
chlorine, oxygen, etc., which they replace in compounds. 

Constitution of salts. Of the supposed combinations of binary compounds, 
with binary compounds, the most numerous and important class are salts. 
Sulphate of soda is commonly viewed as a direct combination of sulphuric 
acid and soda, each preserving its proper nature in the compound; and so 
are all similar compounds of an acid oxide with a basic oxide. An oxygen 
acid is allowed to exist in them, and they are particularly distinguished as 
" oxygen-acid salts." But an opinion was promulgated long ago by Davy, 
that these salts might be constituted on the plan of the binary compounds of 
the former class, and their hydrated acids on the plan of a hydrogen acid; a 
view which is supported by many analogies, and has latterly had a preference 
given to it by some of our leading chemical authorities. It is, therefore, 
deserving of serious consideration. 

One class of acids, the hydrogen acids, and the salts which they produce 
with alkalies, are unquestionably binary compounds, and were assumed by 
Davy as the types of acids and salts in general. Hydrochloric acid is com- 
posed of two elements, chlorine and hydrogen, and with soda it forms water 
and chloride of sodium, thus: 

Hydrochloric acid S Hydrogen. . -^ Water. 

£ Chlorine. 



Soda. C Oxygen. 

I Sodium. . 2^ Chloride of sodium. 




CONSTITUTION OF SALTS. 131 

the hydrogen of the acid being replaced by sodium in the salt formed. Hy- 
drocyanic is another hydrogen acid, of which cyanide of sodium is a salt. In 
general terms, a radical (which may be either simple or compound, like chlo- 
rine or cyanogen) forms an acid with hydrogen, and a salt with sodium or 
any other metal. 

Hydrated sulphuric acid, which consists of sulphuric acid and an atom of 
water, HO -f S0 3 , is represented as a hydrogen acid by transferring the oxy- 
gen of the water to the sulphuric acid, to form a new radical, S0 4 , which is 
supposed to be in direct combination with the remaining atom of hydrogen, as 
H -j- S0 4 . In sulphate of soda, the oxygen of the soda is in the same man- 
ner transferred to the acid, or the formula of the salt is changed from NaO + 
SO 3 to Na+ S0 4 . To S0 4 , which is generally spoken of as the " sulphate 
radical," the name sulphat-oxygen may be applied, and its compounds be 
called sulphat -oxides; and then the acid and salt will be thus named and de- 
noted on the two views of their constitution: 

Old view: 
Hydrated sulphuric acid or sulphate of 

oxide of hydrogen. . HO-f-S0 3 

Sulphate of soda or sulphate of oxide of 

sodium. ... NaO-r-S0 3 

New view: 
Sulphatoxide of hydrogen. . . H -f S0 4 

Sulphatoxide of sodium. . . Na + S0 4 ; 

which last formulae are strictly comparable with those of an admitted hydrogen 
acid and its salt, such as: 

Hydrochloric acid or chloride of hydro- 
gen H + CI 

Chloride of sodium. . . . Na -f CI; 

as: 

Hydrocyanic acid or cyanide of hydro- 
gen H + NC 2 

Cyanide of sodium. . . . Na -f- NC 2 ; 

which thus appear compounds of three different radicals, chlorine (CI,) cyano- 
gen (NC 2 ) and sulphatoxygen (S0 4 ,) with the same elementary bodies, hy- 
drogen and sodium. Sulphatoxygen is known only in combination, and has 
not been obtained in a separate state like chlorine and cyanogen. The body, 
sulphuric acid, S0 3 , which may be separated from some sulphates and can ex- 
ist by itself, is supposed to be a product of their decomposition and not to 
pre-exist in these salts, so that it has a secondary character assigned to it. 

Hydrated nitric acid, or aqua fortis, becomes a hydrogen acid, by the crea- 
tion of a nitrate radical, nitratoxygen. It is the nitratoxide of hydrogen instead 
of the nitrate of water. 

H + NO,, instead of HO + NO,. 
The nitrate of potash becomes the nitratoxide of potassium, and so of all 
other nitrates. The existence of nitratoxygen is hypothetical, as it has not been 
insulated, but in this respect it is not otherwise situated than nitric acid itself, 
which cannot be exhibited in a separate state, and is believed to be capable of 
existing only in a state of combination. 

It is evident that the same view is applicable to hydrated oxygen acids in 
general, which may be made hydrogen acids, by assuming the existence of a 
new radical for each, containing an atom more of oxygen than the oxygen 
acid itself, and capable of combining directly with hydrogen and the metals. 
The class of oxygen-acid salts is thus abolished, and they become binary com- 



132 ARRANGEMENT OF THE ELEMENTS IN COMPOUNDS. 

pounds like the chlorides and cyanides. Even oxygen-acids themselves can no 
longer be recognised. It is not sulphuric acid (S0 3 ,) but what was formerly 
viewed as its compound with water, that is the acid, and it is a hydrogen acid. 
The properties which characterize acids are undoubtedly only observed in the 
hydrates of the oxygen acids. Thus the anhydrous sulphuric acid does not 
redden litmus, and exhibits a disposition to combine with salts, such as chlo- 
ride of potassium and sulphate of potash, rather than with bases. The 
liquid carbonic acid has little affinity for water, does not combine directly 
with lime, but dissolves in alcohol, ether and essential oils like certain neutral 
bodies. It is only when associated with water that the bodies referred to ex- 
hibit acid properties, and then hydrogen acids may be produced.* 

On this view it is obvious that the acid and salt are really bodies of the same 
constitution,! hydrochloric acid being the chloride of hydrogen, as common 
salt is the chloride of sodium, and sulphuric acid and sulphate of soda, being 
the sulphatoxides of hydrogen and of sodium. The acid reaction and sour 
taste are not peculiar to the hydrogen compound and do not separate it 
from the others, the chloride, sulphatoxide and nitratoxide of copper being 
nearly as acid and corrosive as the chloride, sulphatoxide and nitratoxide of 
hydrogen, and clearly bodies of the same character and composition. They 
are all equally salts in constitution. The theory in question, therefore, is truly 
a theory of salts, and might be distinguished as " the theory of Binary Salts," 
or some such name, with more propriety than the theory of hydrogen acids. 
The term " acid" is not absolutely required for any class of bodies included 
in the theory, and might, therefore, be dropt, if it were not that an inconve- 
nience would be felt inhavingno common name for the hydrogen compounds, 
which have so many common uses. But overlooking this consideration, the 
supporters of this theory might, perhaps, simplify the expression of it, and 
conciliate their opponents by allowing that class of bodies to retain the name 
of acid which first bore it, although, of course, in a sense consistent with their 
own views. It would then be such bodies as anhydrous sulphuric acid (S0 3 ), 
anhydrous nitric acid (N0 5 ,) that would compose the class of " acids;" and 
in considering the generation of salts, three orders of bodies would be admitted, 
as in the following tabular exposition of a few examples: 

* ["This argument should be considered in reference to two different cases, in one of 
which all the water held by the acid is in the state of a base while in the other an addi- 
tional quantity is present acting as a solvent. So far as water, acting as a solvent, facilitates 
the reaction between acids and bases, it performs a part in common with alcohol, ether, vola- 
tile oils, resins, vitrefiable fluxes, and caloric. Its efficacy must be referred to the general law, 
that fluidity is necessary to chemical reaction. "Corpora non agunt nisi soluta." 

In a majority of cases, basic water, unaided by an additional portion acting as a solvent, 
is quite incompetent to produce reaction between acids and other bodies. Neither between 
sulphuric acid and zinc, between nitric acid and silver, nor between glacial or crystallized 
acids and metallic oxides, does any reaction take place without the aid of water acting as 
a solvent, and performing a part analogous to that which heat performs in promoting the 
union of those oxybases with boric, or silicic acid. 

It is only with soluble acids that water has any efficacy. The difference between the 
energy of sulphuric and silicic acid, under the different circumstances in which they can 
reciprocally displace each other, is founded on the nature of the solvents which they re- 
quire, the one being only capable of liquefaction by water, the other by caloric." 

An effort to refute the argument in favour of the existence in the amphide salts of radi. 
cals, &c. By Robert Flare, M. D. Prof, of Chemistry in the University of Penn. p. 15.] 

t [" I agree perfectly with Gregory in considering that hydrated acids may be considered 
as "hydrogen salts." But when the learned editor proceeds to allege that " acids and salts, 
as respects their constitution, will form one class,'''' I consider him, and those who sanction 
this allegation, as founding an error upon oversight. Because the salts of hydrogen, or 
such as have water for their base, have heretofore been erroneously called acids, we are 
henceforth to confound salts with acids, and instead of correcting one wrong name, cause 
all others to conform thereto !"] Hare's Effort, p. 8. 



CONSTITUTION OF SALTS. 133 



I. 

The acid. 


II. 

The salt-radical. 


III. 

The salt. 


S0 3 


S0 4 


S0 4 -fHoraMetal. 


NO, . 


N0 6 


N0 6 -fHoraMetal. 




NC 3 


NC 2 -f-HoraMetal. 




CI 


Cl+HoraMetal. 



The first term of the series, or " the acid," is wanting in the last two examples, 
and that is the peculiarity of those bodies which constituted the original class of 
hydrogen acids and their salts. While the old class of oxygen-acid salts have 
both a radical and an acid, as in the first two examples. 

The peculiar advantages of the Binary Theory of Salts, are — 
First : That instead of two it makes but one great class of salts, assimilating 
in constitution bodies which certainly resemble each other in properties. Chlo- 
ride of sodium and sulphate of soda are both neutral, and possess a common 
character, which is that of a soda-salt, but they are separated widely from each 
other on the ordinary view of their constitution which is expressed in their 
names* 

Secondly: It accounts for a remarkable law which is observed in the con- 
struction of salts ; namely, that bases always combine with as many atoms of 
acid, as they themselves contain of oxygen : a protoxide, which contains one 
atom of oxygen combining and forming a neutral salt with one atom of an ox- 
ygen acid ; while an oxide which contains two atoms of oxygen to one of metal, 
like peroxide of tin, forms a neutral salt with two atoms of acid ; and an oxide 
of three atoms of oxygen to two of metal, like peroxide of iron, forms a neutral 
salt with three atoms of acid. The acid and oxygen are thus always together 
in the exact proportion to form the salt-radical, there being always an atom of 
oxygen for every atom of acid in the salt. This will appear more distinctly in 

["* I presume it will be granted, that if similitude in properties be a sufficient ground for 
inferring an analogy in composition, dissimilitude ought to justify an opposite inference. 
And that if as the author alleges, certain bodies have been classed as salts, on account of 
their similarity in this respect, when dissimilar they ought not to be so classed. Under 
this view of the question, I propose to examine how far any similitude in properties ex- 
ists between the bodies designated as salts by the author or any other chemist. 

The salts hitherto considered as compounds of acids and bases are by Berzelius called 
amphide salts, being produced severally by the union with one or other of his amphigen 
class, comprising oxygen, sulphur, selenium, and tellurium, with two radicals, with one of 
which an acid is formed, with the other a base. The binary compounds of his halogen 
class, comprising chlorine, bromine, iodine, fluorine and cyanogen, are called by him 
haloid salts. I shall use the names thus suggested. 

Among the haloid salts we have common salt and Derbyshire spar; the gaseous fluo- 
rides and chlorides of hydrogen, silicon or boron; the fuming liquor of Libavius; 
the acrid butyraceons chlorides of zinc, bismuth and antimony ; the volatile chlorides of 
zinc, bismuth and antimony ; the volatile chlorides of magnesium, iron, chromium, and 
mercury, and the fixed chlorides of calcium, barium, strontium, silver, and lead ; 
the volatile poison prussic acid, and solid poisonous bicyanide of mercury, with various 
inert cyanides like those of Prussian blue : likewise a great number of etherial compounds. 

Among the amphide are the very soluble sulphates of zinc, iron, copper, soda, magnesia, 
&c, and the insoluble stony sulphates of baryta and strontia ; also ceruse and sugar of 
lead; alabaster, marble, soaps, ethers, and innumerable stony silicates, and aluminates. 
Last, but not among the least discordant, are the hydrated acids, and alkaline and earthy 
hydrates. 

When the various sets of bodies, above enumerated, as comprised in the two classes un- 
der consideration, are contemplated, is it evident that, not only between several sets of 
haloid and amphide salts, but also between several sets in either class, there is an extreme 
discordancy in properties : so that making properties the test would involve not only that 
various sets in one class could not be coupled with certain sets in the other, but, also, that 
in neither class could any one set be selected as exemplifying the characteristics of a salt, 
without depriving a majority of those similarly constituted, of all pretensions to the saline 
character ?"— Hare's Effort, p. 10.] 
12 



134 ARRANGEMENT OF THE ELEMENTS OF COMPOUNDS. 

the following formulae which exhibit the composition of the neutral sulphates of a 
metal in four different states of oxidation, an atom of metal being represented by M. 

Formulae of neutral sulphates.. 

I. II. 

As consisting of As consisting of metal 

oxide and acid and salt radical 

MO-f-S0 3 . M + S0 4 . as in sulphate of soda. 

M 2 0-fS0 3 . M 2 -fS0 4 . as in sulphate of suboxide of mercury. 

M0 2 -j-2S0 3 . M-f-2S0 4 . as in sulphate of peroxide of tin. 

M 2 3 -f-3S0 3 . M 2 -f3S0 4 . as in sulphate of peroxide of iron. 

The acid is seen in the first column to be always in the proper proportion to 
form a sulphatoxide of the metal in the second column ; and these sulphatoxides 
correspond exactly with known chlorides, such as M CI, M 2 CI, M Cl 2 , M„ Cl 3 .* 

Thirdly: It offers a more simple and philosophical explanation of the 
action of certain metals upon acid solutions, and of the decomposition of 
such solutions in other circumstances. Thus when zinc is introduced into 
hydrochloric acid, it is allowed on both views, that the metal simply dis- 
places the hydrogen which is evolved, and that chloride of zinc is formed 
in the place of chloride of hydrogen. In the same way when zinc is introduced 
into diluted sulphuric acid which contains the sulphatoxide of hydrogen 
on the binary theory, hydrogen is simply displaced and evolved as be- 
fore, and the sulphatoxide of zinc formed instead of the sulphatoxide of hydro- 
gen, t The metal in question appears to be incapable of decomposing pure 
water by displacing its hydrogen at the temperature of the air ; but this fact 



[" * I have already adverted to the existence of certain chemical laws, inexplicable in 
the present state of human knowledge. Among these is that of the necessity of oxidation 
to enable metallic radicals to combine with acids. But as a similar mystery exists as re- 
spects the adventitious property of combining with radicals, which results from the acqui- 
sition of an additional atom of oxygen by any of the compounds hitherto considered as 
anhydrous acids, the new doctrine has in that respect no pre-eminent claim to credence. 

But if, without impairing the comparative pretensions of the prevailing doctrine, we may 
appeal to the fact that the acquisition of an atom of oxygen confers upon a radical the ba- 
sic power to hold one atom of acid, is it not consistent that the acquisition of two atoms of 
oxygen should confer the power to hold two atoms of acid, and that with each further ac 
quisition of oxygen a further power to hold acids should be conferred ? 

So far then there is in the old doctrine no more inscrutability than in that which has 
been proposed as its successor. Since if on the one hand it be requisite that for each atom 
of oxygen in the base, there shall be an atom of acid in any salt which it may form, on 
the other, in the case of the three oxyphosphions, for each additional atom of hydrogen 
extraneous to the salt radical, there must bean atom of oxygen superadded to this radical." 
—Hare's Effort, p. 14.] 

[ w f When oxide of copper is presented to chlorohydric acid, it is inferred that the 
hydrogen unites with oxygen, and the chlorine with the metal, and hence it seems to be 
presumed, that when oxide of copper is combined with sulphuric acid, a similar play of 
affinities should ensue : but would it be reasonable to make this a ground for assuming the 
existence of a compound radical, when the phenomena admit of another explanation quite 
as simple and consistent with the laws of chemical affinity ? 

Whether hydrogen be replaced by zinc, or oxide of hydrogen by oxide of copper, cannot 
make any material difference. In one case a radical expels another radical, and takes its 
place; in the other, a base expels another base, and takes its place. 

There can be no difficulty, then, in understanding wherefore, from the compound of sul. 
phur and three atoms of oxygen, and an atom of basic water, hydrogen should be expelled 
and replaced by zinc, or that water should be expelled and replaced by oxide of copper ; the 
only mystery is in the facts, that SO 3 , as anhydrous sulphuric acid, will not combine with 
hydrogen, copper or any other radical, unless oxydized. But this mystery equally exists 
on assuming that an additional atom of oxygen converts SO 3 into oxysulphion Csnlphatox- 
ygen,) endowed with an energetic affinity for metallic radicals, to which SO 3 is quite 
indifferent."— Hare's Effort, p. 9.] 



CONSTITUTION OF SALTS. 135 

does not interfere with the preceding explanation, as zinc may have a greater 
affinity for sulphatoxygen than for oxygen, and, therefore, be capable of decom- 
posing the sulphatoxide, but not the oxide of hydrogen. If the acid solution, 
however, contains sulphate of water, as it does on the old view, then zinc does 
and does not decompose water, decomposing it when in combination but not 
when free. It then becomes necessary to assume that the presence of the acid 
enhances the affinity of the metal for the oxygen of the water in a manner which 
cannot be clearly explained; for the solubility of oxide of zinc in the acid, to 
which its influence is generally ascribed, accounts for the continuance of the ac- 
tion, by providing for the removal of the oxide, rather than for its first com- 
mencement * The phenomena of the decomposition of an acid solution by 
electricity, are also most simply explained on the binary theory. Oxide of hydro- 
gen and sulphatoxide of hydrogen, are both binary " electrolytes," which are de- 
composed by the electric current in the same manner, although not with equal 
facility, the common element, hydrogen, proceeding from both to the negative 
electrode, and the oxygen in the one case and the sulphatoxygen in the other 
to the positive electrode. The sulphatoxygen finds water there, and resolves 
itself into sulphatoxide of hydrogen and free oxygen. The decomposition of 
the sulphatoxide of sodium or any other salt may be explained in the same 
simple manner ; while on the other view, it must be assumed that a simulta- 
neous transference between the electrodes of acid and alkali with the oxygen 
and hydrogen of water takes place; and the effect of the acid in promoting the 
decomposition of the water remains unaccounted for.f 

When a metallic oxide is dissolved in an acid solution, as oxide of zinc in di- 
luted sulphuric acid, the reaction which occurs is thus explained on the binary 
theory : 

Sulphatoxide C Hydrogen . ., ^ Water. 

of hydrogen. I Sulphatoxygen 

Oxide of C Oxygen 

zinc. £ Zinc •, • • ^ Sulphatoxide of zinc; 

as in the reaction between the same oxide and hydrochloric acid (page 130.) 



["* But if the sulphate of water owe its energy to that portion of this liquid, which, by 
its decomposition gives rise to the compound radical oxysulphion, and not to the portion 
which operates as a solvent, wherefore in the concentrated state, will it not react with iron 
and zinc, without additional water, when, with dilution, it reacts most powerfully with those 
metals."— Hare's Effort, p. 16.] 

[" t It appears to me, that the simultaneous appearance of the elements of water, and 
of acid and aJka.Fl, at the electrodes, as above staled, may be accounted for, simply by that 
eleclrolyzation of the soda, which mast be the natural consequence of the exposure of the 
sulphate of that base in the circuit. I will, in support of the exposition which I am about 
to make, quote the language of Professor Daniell, in his late work, entitled, ' Introduction 
to Chemical Philosophy,' page 413 : — " 

'Thus we may conceive that the force of affinity receives an impulse which enables the 
hydrogen of the first particle of water, which undergoes decomposition, to combine momen- 
tarily with the oxygen of the next particle in succession; the hydrogen of this again, with 
the oxygen of the next; and so on till the last particle of hydrogen communicates its im- 
pulse to the pla inum, and escapes in its own elastic form.' 

The process here represented as taking place in the instance of the oxide of hydrogen, 
takes place, of course, in that of any other electrolyte. 

It is well known, that when a fixed alkaline solution is subjected to the voltaic current, 
that the alkali, whether soda or potassa, is decomposed ; so that if mercury be used for the 
cathode, the nascent metal, being protected by uniting therewith, an amalgam is formed. 
If the cathode be of platinum, the metal, being unprotected, is, by decomposing water, re- 
converted into an oxide as soon as evolved. This shows, that when a salt of potassa or 
soda is subjected to the voltaic current, it is the alkali which is the primary object of attack, 
the decomposition of the water being a secondary result." — Hare's Effort^. 17.] 




136 ARRANGEMENT OF THE ELEMENTS IN COMPOUNDS- 

The chief objections to the binary theory of salts, are — 

First : The creation of so many hypothetical radicals ; namely, one for every 
class of oxygen-acid salts. But it is to be remembered that the great propor- 
tion of oxygen acids, such as nitric, acetic, oxalic, &c., are equally of an ideal 
character and cannot be exhibited in a separate state. 

Secondly: The peculiarities of the salts of phosphoric acid are supposed to be 
inimical to the new view. That acid forms three different and independent classes 
of salts, containing respectively one, two and three atoms of base to one of acid. 
On the binary theory, these three classes of salts must contain three different 
radicals, combined respectively with one, two and three atoms of hydrogen or 
metal. The three phosphates of water and the corresponding phosphatoxides of 
hydrogen would be represented as follows : 

HO + P0 5 . 2Ho+P0 5 . 3HO+P0 5 

H+P0 6 . 2H + P0 7 . 3H + P0 8 

Such radicals and such compounds with hydrogen startle us from their novelty, 
but it may be questioned whether they are really more singular than the anor- 
mal classes of phosphates, containing several atoms of base, for which they are 
substituted, but which we have been more accustomed to contemplate.* All the 
salt-radicals known in a separate state, such as chlorine and cyanogen, combine 
with one atom only of hydrogen or metal, but it would be unfair to assume in 
the present imperfect state of our knowledge that other radicals may not exist, 
capable of combining with two or three atoms of metal, as the phosphate radi- 
cals are supposed to do. The existence of at least one such radical is highly 
probable, as will afterwards appear. 

In conclusion, it may be stated that neither view of the constitution of the 
oxygen-acid salts, (which are alone affected by this discussion,) rests on demon- 
strative evidence — they are both hypotheses and are both capable of explaining 
all the phenomena of the salts. But to whichever of them we give a preference, 
we can scarcely avoid using the language of the old theory in the present state 
of chemical science. 

Without deciding definitively in favour of one* or other of these views, a dis- 
tribution of the great class of salts into three orders may be made. A certain 
number of salts contain radicals which can be isolated, others oxygen-acids 
which can be isolated, while others have yet afforded neither radical nor acid in 
a separate state. Hence, there are : 

1. Salts of isolable radicals: chlorides, cyanides, sulpho-cyanides, &c. 

2. Salts of isolable acids : sulphates, carbonates, &c. 

3. Salts which contain neither an isolable radical nor an isolable acid : ni- 
trates, acetates, hyposulphites, &c. Even admitting that all salts have the same 
constitution, the capability of breaking up in such different ways must affect 
their modes of decomposition in different circumstances, and produce distinctions 
in properties, which would render such a division of them expedient. 

[* " Besides the three oxyphosphions, of which the formulas are above stated, there 
would have to be another in the phosphites ; so that instead of the hydrated acid, or phos- 
phite of water, being P0 3 f- HO, it would have to be P0 4 -f- H, a fourth oxyphosphionide 
of hydrogen. 

To me the formation of three compound elements, by the reiterated addition of an atom, 
of which five of the same kind were previously in the mass to which the addition is made, 
seems more anomalous, mysterious, and improbable, than the existence of three compounds 
of phosphoric acid with water, in which the presence of the different proportions of water 
is the consequence of some change in the constitution of the elements which is referred to 
isomerism. 

No reason can be given why the addition of one, lioo and three atoms of oxygen, to the 
" radical," should convey a power to hold a proportional number of atoms of hydrogen. 
Such an acquisition of power is an anomaly." — Hare's Effort, p. 13.] 



CONSTITUTION OF SALTS. 137 

It has become necessary to recognise three classes of oxygen-acid salts, 
which in the language of the old theory contain, one, two, and three atoms of 
base to one of acid. 

1. Monobasic suits. — The great proportion of acids, such as sulphuric, ni- 
tric, <fcc, neutralize but one atom of base, and form, therefore, monobasic salts. 
But this is not inconsistent with an acid's forming two series of salts with the 
same base or class of isomorphous bases. Thus there appear to be two well 
marked classes of sulphates of the magnesian oxides, which agree in having 
one atom of base, but differ essentially in the proportions of combined water 
which they affect. In one series the sulphate is combined with one, three, 
five, or seven atoms of water. Copperas (a sulphate of iron,) epsom salt (a 
sulphate of magnesia,) blue vitriol (a sulphate of copper,) and most of the 
well known magnesian sulphates belong to this class; which may be called the 
copperas class of sulphates. All the members of it are very soluble in water, 
and form double salts with sulphate of potash. The other series affect two, 
four, and six atoms of water. They are less known, but appear to be of 
sparing solubility, and to be incapable of forming double salts with sulphate of 
potash. Gypsum or sulphate of lime belongs to this class, which may, there- 
fore, be called the gypsum class of magnesian sulphates. Sulphate of iron 
crystallizes from solution in sulphuric acid with two atoms of water, with the 
crystalline form and sparing solubility of gypsum. Dr. Kane obtained a sul- 
phate of copper with four atoms of water, by exposing the anhydrous salt to 
the vapour of hydrochloric acid, which appears to be the second term in this 
series; and Mitseherlich still maintains the existence of a peculiar sulphate of 
magnesia containing six atoms of water of crystallization, which will constitute 
the third term. It is evident that the cause of such double classes of salts is 
as deeply seated as that of dimorphism, and hence, possibly, the magnesian 
sulphate itself, which exists in the two classes, is not the same in its constitu- 
tion with reference to heat. 

2. Bibasic salts. — That class of phosphates, which received the name of 
pyrophosphates, was the only class of salts, known till lately, in which one 
atom of acid neutralizes two atoms of base. But according to the recent results 
of Fremy which have been favourably reported upon by Dumas,* the classes 
of tartrates and racemates which have long been known to chemists, are also 
bibasic salts. It is the character of a bibasic acid to unite at once with two 
different bases, which accounts for the formation of Rochelle salt, the tartrate 
of potash and soda, of which the formula is KO, NaO-f C 3 U 4 O l 9 . Liebig 
has also lately shown that gallic acid is bibasic,t the gallate of lead being thus 
composed 2PbO + C 7 H0 3 . Now if we attempt to make this a monobasic 
salt by dividing the atoms both in base and acid by two, an atom of gallic acid 
would come to contain half an equivalent of hydrogen, which Liebiff considers 
as conclusive against the division of its atomic weight. Lactic acid also is 
likely to prove bibasic. 

3. Tribasic salts. — The tribasic phosphates have proved to be the type of 
a class of salts. One atom of arsenic acid neutralizes three atoms of base; 30, 
it is probable, does one atom of phosphorous acid. Tannic acid also saturates 
three atoms of base, the formula of the tannate of lead being 3PbO+ C 13 H 5 9 
(Liebig.) There is the same necessity to admit that citric acid is tribasic, 
and the formula of a citrate 3MO+ C^U. 5 lli (in which M represents an 
atom of metal or of hydrogen) as there is to allow that gallic acid is bibasic. 
Most of the citrates contain two atoms of fixed base, and one of water, but the 
citrate of silver contains three atoms of oxide of silver. Cyanuric, fulminic 
and cyanic acids are isomeric, and all tribasic according to Liebig, and as he 



* L'Institut, May, 1838, page 141. t Ibid. 

12* 



138 ARRANGEMENT OF THE ELEMENTS IN COMPOUNDS. 

has also lately ascertained with respect to the related acids, meconic, metame- 
conic, and pyromeconic, are respectively tribasic, bibasic, and monobasic* 

Two of the three atoms of base in this class of salts may be different as is 
observed in certain citrates, cyanurates, and phosphates, or the whole three 
may be different as in the phosphate called microsmic salt, which contains at 
once soda, oxide of ammonium and water as bases. f Two or more of the 
bases may likewise be isomorphous, or at least belong to the same natural 
family as soda and oxide of ammonium, water and magnesia. This class and 
the last will probably be rapidly augmented by the addition of organic acids. 
Dumas considers it probable that the organic acids which are not volatile, like 
tartaric and citric acids, have all a high atomic weight, which causes them to 
be fixed, and that the received equivalents of some of them may, therefore, 
require to be increased, which would afford room for viewing them as bibasic 
or tribasic. 

Salts usually denominated Submits, The preceding classes of salts, and 
many other bodies also are capable of combining with a certain proportion of 
water, generally vaguely spoken of as water of crystallization. The com- 
pounds of the present class appear to be salts which have assumed a fixed me- 
tallic oxide in the place of this water. They may, therefore, be truly neutral 
in composition, the excess of oxide not standing in the relation of base to the 
acid. I have elsewhere shown that crystallized nitrate of copper, nitrate of 
water, (acid of sp. gr. 1.42,) and subnitrate of copper, may be represented by 
the formula, CuO, NQ 5 +3HO; HO, N0 5 + 3HO; and HO, N0 5 -r-3CuO, 
and have distinguished as constitutional, the three atoms of water which exist in 
these and all the magnesian nitrates, and which are replaced by three atoms of 
oxide of copper in the subnitrate of copper, which is, therefore, a nitrate of 
water with constitutional (not basic) oxide of copper, a view which is ex- 
pressed by the arrangement of the symbols in its formula.;}; Water, oxide of 
copper and oxide of lead appear to be the bodies most disposed to attach them- 

* Letter from M. Liebig, dated April, 2, 1838. 

t Inquiries respecting the constitution of salts; of oxalates, nitrates, phosphates, sul- 
phates and chlorides. Fhil. Trans. 1837, page 47. 

t [In the above theory of subsalts is exhibited one of the difficulties involved in the adop. 
tion of the " binary theory of salts." As long as this latter theory is applied to neutral 
salts or to those salts only which are constituted according to the law (p. 133,) that "bases 
always combine with the same number of atoms of acid as they themselves contain of oxy- 
gen," the subject is without difficulty ; but extend the application to the salts in which the 
atoms of oxygen in the base are not in the same number as the atoms of acid and imme- 
diately the theory fails. It becomes necessary either to assume the existence of a new 
salt radical or to propound a new theory to supply the deficiency of the former. This may 
be seen by examining the formula above given, for subnitrate of copper, in which two 
equivalents of base exist in excess over and above what is sufficient to form nitratoxide of 
copper and which could only be explained as in the text or by assuming a new salt radical 
NO,4-0 3 and this radical capable of uniting with three equivalents of a metallic radkal. 

There are also other salts neutral in character, which as they do not agree with the law 
above referred to, also do not correspond with the binary theory of salts.. The following 
example may be taken from the salts of tartaric acid; which considered as a bibasic aeid 
is constituted according to the formula C 8 H 4 O 10 , substituting for this formula the sym- 
bol "T we have the four of the salts represented as follows, according to the old and new 
views : __ 

T 4- KO, HO = T0 2 4- K, H, Cream of tartar. 
"T-f KO, NaO = T0 2 + K, Na, Rochelle salt. 
T" 4- KO, F 2 3 =T0 4 4- K, Fe 2 ,Tartarized iron. 
T*4- KO, Sb0 3 =~T0 4 + K, Sb, Tartar emetic. 
In the first two formulae the elements are readily transposed to suit either view; but in the 
two latter a new hypothetical salt radcal becomes, necessary and with new powers, viz. 
the capability of combining respectively with two atoms of metallic radical K, Sb, and 
with three atoms of metallic radical K, Fe 2 . R. B.] 



CONSTITUTION OF SALTS. 139 

selves to salts in this manner. The strong alkalies, potash and soda are never 
found in such a relation, or discharging any other function than that of base to 
the acid of the salt. These views of subsalts, in which their constitutional 
neutrality is preserved, have been adopted byLiebig and Dumas, and extended 
to organic compounds. Many neutral organic bodies appear to be capable of 
combining with metallic oxides particularly with oxide of lead, such as sugar, 
amidine, dextrine, orcine, and they generally combine with several atoms of 
the oxide; the neutral bodies mentioned being fixed and probably possessing 
a high atomic weight. Thus in the compound of orcine and oxide of lead, 
C l8 H 8 3 -f 5PbO, the orcine must be present in the proportion of one 
atom, as the numbers of its constituent atoms have no common divisor; and 
the orcine, therefore, is combined with five atoms of constitutional oxide of 
lead, which actually replace five atoms of constitutional water which orcine 
otherwise contains. 

Constitutional water is sometimes replaced by a salt, which never happens 
with basic water. Thus starch or grape sugar, in its ordinary hydrated state, 
consists of C 12 H 12 J2 -f-2HO; of which the two atoms of water may be re- 
placed by chloride of sodium, and the compound formed, C 12 H I2 12 -f2 
NaCl. It is to be observed that constitutional water is combined with a salt 
rather than in it, and such an element is removed and replaced without affect- 
ing the structure of the body to which it may be said to be attached. The 
replacing substance may also be a compound of a very different character from 
water, for besides metallic oxides and salts, ammonia and certain anhydrous 
acids appear to be capable of attaching themselves to salts, in the same man- 
ner as constitutional water. 

Suits of the type of red chromate of potash. Several salts unite with anhy- 
drous acids. Thus both chloride of sodium and chloride of potassium absorb 
and combine with two atoms of anhydrous sulphuric acid without decom- 
position, when exposed to the vapour of that substance. Sulphate of potash 
also combines with one atom of anhydrous sulphuric acid. All these com- 
pounds are destroyed by water. But the red chromate of potash, generally 
called bichromate of potash, which consists of chromate of potash together 
with one atom of chromic acid, is possessed of greater stability, as is likewise 
the compound of chloride of sodium or potassium with two atoms chromic 
acid. The red chromate might be viewed as a chromate of the chromate of 
potash, and the last two compounds as bichromates of the chlorides of potas- 
sium and sodium, but these expressions are more convenient than philosophi- 
cal, and it will be safer in the present state of our knowledge to assimilate 
these salts in composition to the combinations of neutral bodies with consti- 
tutional water, particularly as we find the proportion of acid to be variable, 
and generally to be more than one atom. Thus a compound is known con- 
taining one atom of potash and three of chromic acid, which may be viewed 
as a combination of chromate of potash with two atoms of chromic acid, 
and represented by KO, Cr0 3 ■+■ 2Cr0 3 . The red chromate of potash will 
then be KO, Cr0 3 + CrO r And the chromate containing chloride of potas- 
sium, KC1 -f- 2Cr0 3 . The biniodate of potash (iodate of water and potash) 
may be rendered anhydrous, and while so, is a salt of this class. 

Double Salts. Salts combine with each other, but by no means indiscrimi- 
nately. With a few exceptions which may be placed out of consideration for 
the present, the combining salts have always the same acid, sulphates com- 
bining with sulphates, chlorides with chlorides. Their bases or their metals, 
however, must belong to different natural families. Thus it may be questioned 
whether a salt of potash ever combines with a salt of soda, certainly never 
with a salt of ammonia. Salts of the numerous metals, including hydrogen, 
belonging to the magnesian family do not combine together; thus sulphate of 



140 ARRANGEMENT OF THE ELEMENTS IN COMPOUNDS. 

magnesia does not form a double salt with sulphate of lime, with sulphate of 
$inc, or with sulphate of water. While on the other hand salts of this family- 
are much disposed to combine with salts of the potassium family; sulphate of 
soda, for instance, forming double salts with sulphate of lime, sulphate of zinc 
and sulphate of water. We have thus the means of distinguishing between a 
double salt, and the salt of a bibasic or tribasic acid. The bisulphate and 
binoxalate of potash, saturated with soda, form sulphates and oxalates of 
potash and soda, which separate from each other by crystallization, although 
the acid salts are themselves double salts of water and potash. But the acid 
fulminate of silver, or the acid tartrate of potash (bitartrate) affords only one 
salt when saturated with soda, in which isomorphous bases exist, and which, 
therefore, is a salt of one acid, and not a compound of two salts. The great 
proportion of the salts which are named super, acid and 6i-salts, contain a 
salt of water and are double salts, such as the supercarbonate of soda (HO, 
C0 2 -f NaO, C0 2 ,) the acid sulphates of potash and the binacetate of soda; 
but a few of them are bibasic or tribasic salts, containing one or two atoms of 
water as base, such as the salt called bitartrate of potash, and biphosphate of 
potash (2HO, KO+P0 5 .) 

There is no parallelism between the constitution of a double salt, or that of a 
simple salt itself, or foundation for the statements which are sometimes made, 
that one of the salts which compose a double salt has the relation to the other of 
an acid to a base, and that one salt is electro-negative to the other. The reso- 
lution of a double salt into its constituent salts by electricity, has never been ex- 
hibited, and is not to be expected from what is known of electrolytic action. 
While no analogy whatever subsists between a double salt and a simple salt on 
the binary view of the constitution of the latter. Besides, the supposed analogy 
is destroyed by what is known of the derivation of double salts. Sulphate of 
magnesia acquires an atom 'of sulphate of potash in the place of an atom of 
water which is strongly attached to it, in becoming the double sulphate of mag- 
nesia and potash. In the same way, the sulphate of water has an atom of water 
also replaced by sulphate of potash, in becoming the bisulphate of potash; rela- 
tions which appear in the rational formulae of these salts: 

Sulphate of magnesia .... Mg # S(H) + 6H 

Sulphate of magnesia and potash . . Mg S (K S)-f 6H 
Sulphate of water (acid of sp. gr. 1.78) . H S*(H) 
Bisulphate of potash ."'"'. . . . H S* (K S) 
It thus appears that a provision exists in sulphate of magnesia itself for the for- 
mation of a double salt, and that the molecular structure is Unaltered, notwith- 
standing the assumption of the sulphate of potash as a constituent. The deriva- 
tion of the acid oxalates likewise, throws much light on the nature of double 
salts. The oxalate of potash contains an atom of constitutional water, which is 
replaced by hydrated oxalic acid (the crystallized oxalate of water,) in the for- 
mation of the binoxalate of potash (double oxalate of potash and water,) or by 
the oxalate of copper in the formation of the double oxalate of potash and cop- 
per, as exhibited in the following formulae, in which the replacing substances are 
enclosed in brackets to mark them as before : 

Oxalate of potash KCC(H) 

Binoxalate of potash kcC(HCCH 2 ) 

Oxalate of potash and copper . . . K CC (Cu CC H 8 ) 
Now the anomalous salt, quadroxalate of potash, is derived in the same way 
from the binoxalate, as the binoxalate itself is derived from the neutral oxalate, 



CONSTITUTION OF SALTS. 141 

two atoms of water being displaced by two atoms of hydrated oxalic acid thus : 
Binoxalate of potash .... K CC, H CC, (2H) 
Quadroxalate of potash . . . K CC, HCC, (2HCCH 2 ) 

These examples illustrate the derivation of double salts by substitution. The 
structure of the salts too exemplifies what may be called consecutive combina- 
tion. The basis of the last mentioned salt, for instance, is oxalate of potash, 
which is in direct combination with oxalate of water. A compound body is thus 
produced which seems to unite as a whole with two atoms of hydrated oxalic 
acid. This is very different from the direct combination of all the elements 
which compose the salt. 

In the formation of other classes of double salts, no substitution is observed, 
but simply the attachment of two salts together, often of an anhydrous with a 
hydrated salt, in which case the last often carries its combined water along 
with it, and sometimes acquires an additional proportion. Thus in the for- 
mula of the double chloride of potassium and copper, KC14- CuCl, 2HO, 
the formulae of its constituent salts reappear without alteration; and in that 
of alum, sulphate of potash is found with the hydrated sulphate of alumina 
annexed, of which the water is increased from eighteen to twenty-four atoms. 
In these and all other double salts, the characters of the constituent salts are 
very little affected by their state of union.* If one of them has an acid reac- 
tion, like sulphate of alumina or chloride of copper, it retains the same charac- 
ter in combination; and nothing resembling a mutual neutralization of the salts 
by each other is ever observed. 

The compounds of chlorides with chlorides and of iodides with iodides are 
numerous, and were viewed by Bonsdorf as simple salts, in which one of the 
chlorides is the acid, and the other the base. But such an opinion can no 
longer be entertained, the chlorides themselves being unquestionably salts, and 
their compounds, therefore, double salts.t 

The combinations of such salts with each other as contain different acids 
are not so well understood, the theory of their formation having been little at- 
tended to. They are in general decomposed by water, and easily if the solu- 
bility of one of their constituents is considerable, as is observed of the com- 
pounds of iodate of soda with one and with two proportions of chloride of 
sodium, of the biniodate of potash with the sulphate of potash, of the oxalate 
of lime with the chloride of calcium. 

The compound cyanides whic hform a considerable class of salts must be ex- 
cepted from all the preceding general statements*in regard to double salts. Cya- 
nides of the same family combine together, as cyanide of iron with cyanide of 
hydrogen; the compound cyanide also generally consists of three and not of two 
simple cyanides; and lastly the properties of compound cyanides are very diffe- 
rent from those of the simple cyanides which are supposed to compose them. The 
simple cyanide of potassium, for instance, is highly poisonous, while the double 

* ["This allegation being, in the next page, admitted to be inapplicable in the case of 
the double cyanides ; an effort is made to get over this obstacle, by suggesting the existence 
of another compound radical. But the allegation of the author is erroneous as respects various 
double haloid salts, especially the fluosilicates, the fluoborates, fluozirconiates, the chloro- 
platinates, chloroiridiates, chloroosmiates, chloropalladiates, &c, all of them compounds in 
which the constituent fluorides and chlorides exist in a state of energetic combination by 
which they are materially altered as to their state of existence."— Hare's Effort, p. 11.,] 

t "If the oxide of hydrogen be a salt, every oxide is a salt, as well as every chloride. 
Now controverting the argument above quoted, by analogous reasoning, it may be said 
• the oxides themselves being salts, their compounds are double salts? Of course sulphate of 
potash is not a sulphatoxide as Graham's ingenious nomenclature would make it, but must 
be a double salt, since it consists of two oxides in themselves sails." — Hare's Effort, p. 9.] 



142 ARRANGEMENT OF THE ELEMENTS IN COMPOUNDS. 

cyanide of potassium and iron is as mild in its action upon the animal econo- 
my as sulphate of soda. But the compound cyanides may be removed from 
the class of double salts on a speculative view of their constitution, which their 
anomalous character warrants me in proposing. It is to be premised that the 
supposed double proto-cyanide of iron and potassium (yellow prussiate of 
potash) affords no hydrocyanic acid whatever when distilled with an excess of 
sulphuric acid at a temperature not exceeding 100°, which suggests the idea 
that it does not contain cyanides or cyanogen. Assuming the existence of a 
new compound radical, N 3 C 6 , which has three times the atomic weight of 
cyanogen, and may be called prussine, and which is also tribasic or capable 
of combining with three atoms of hydrogen or metal, like the radical of the 
tribasic class of phosphates, then the compound cyanides assume a constitu- 
tion of extreme simplicity. We have one atom of prussine combined always 
with three atoms of hydrogen or metal in the following salts; in the proto- 
cyanide of iron and potassium with one of iron and two of potassium; in the 
compound called ferro-cyanic acid, with one of iron and two of hydrogen; in 
Mosander's salts, with one of iron, one of potassium and one of barium, cal- 
cium, &c; with two of iron and one of potassium in the salt which precipi- 
tates on distilling the yellow prussiate of potash with sulphuric acid at 212°. 
To many of these, parallel combinations might be adduced from the tribasic 
phosphates. Prussides likewise combine together, producing double prus- 
sides, such as: 

Percyanide of iron and potassium 

(red prussiate of potash) . Fe 2 ,N 3 C 6 + K 3 ,N 3 C 6 
.Prussian blue . Fe 2 ,N 3 C 6 +Fe 3 ,N 3 C 6 

Basic prussian blue . . . Fe2,N 3 C 6 4-Fe 3 ,N 3 C 6 +Fe 2 3 

One of the proximate constituents in the class of salts, is always a metal or 
hydrogen on the one theory, or the oxide of a metal or of hydrogen on the other. 
The metal or the oxide in the salt is often spoken of as its radical, or the oxide of 
its radical, expressions which are perfectly correct, but apt to lead to confusion 
from the application of the term " salt-radical " to the other constituent of the 
salt on the binary theory. It may be useful, therefore, to have a specific ex- 
pression for the metallic radical of a salt, such as basyle, a term compounded 
of base, which is applied to the oxide of the metal, and tMu, nature or 'princi- 
ple, a termination already adopted in particular cases in the sense here given 
to it. Thus of sulphate of soda, soda is the base and sodium the basyle; and 
on the binary theory, sulphatoxygen being the salt-radical, sodium is still 
the basyle of the same salt. But the necessity for such a term is chiefly oc- 
casioned by the extension which has been made by chemists of their views 
respecting saline combination to the compounds of ammonia, and to the great 
class of bodies called ethers, in which the existence of a compound basyle is 
recognised discharging the function of the simple metallic radical in ordinary 
salts. 

Salts of Ammonia. Ammonia is a gaseous compound of one atom of nitro- 
gen and three of hydrogen, of which the solution in water is caustic and alka- 
line, and which neutralizes acids perfectly, as potash and soda do. But all its 
oxygen-acid salts contain, besides ammonia, an atom of water which is essential 
to them, and inseparable without the destruction of the salt ; and with this ad- 
ditional constituent, they are isormorphous with the salts of potash. Hydro- 
chloric acid also unites with ammonia without losing its hydrogen, and the com- 
pound or hydrochlorate of ammonia, which is isomorphous with the chloride of 
potassium, contains, therefore, an atom of hydrogen, besides chlorine and am- 
monia. Now, on the theory of these salts, the ammonia with this hydrogen or 



SALTS OF AMMONIA. 143 

that of the water in the oxygen-acid salts, constitutes a hypothetical radical or 
basyle, ammonium, (NH 4 ,) to which allusion has already been made as being 
isomorphous with potassium. This view of the constitution of the salts of am- 
monia will be made obvious by a few examples. 

f ON THE AMMONHJM THEORY. 

Hydrochlorate of ammonia, NH 3 , HC1. Chloride of ammonium, NH 4 , C). 
Sulphate of ammonia, NH 3 HO, S0 3 . Sulphate of oxide of ammonium, NH 4 0, 

S0 3 . 
Nitrate of ammonia, NH 3 HO, N0 5 . Nitrate of oxide of ammonium, NH 4 0, 

N0 5 . 

The application of this theory to the compounds of ammonia with sulphuretted 
hydrogen and sulphur is particularly felicitous. These compounds may be thus 
represented, and placed in comparison with their potassium analogues, NH 4 
being equivalent to K. 

Sulplmret of ammonium .... NH 4 S . HS 

Hydrosulphuret of sulphuret of ammonium (bihydrosul- 

phuret of ammonia) NH 4 S, HS . KS, HS 

Tritosulphuret of ammonium .... NH 4 S 3 • KS 3 

Pentasulphuret of ammonium .... NH 4 S 5 . KS 5 

Ammonium is supposed to present itself in a tangible form and in possession 
of metallic characters, in the formation of what is called the ammomacal amal- 
gam. When mercury alloyed with one per cent, of sodium is poured into a sa- 
turated cold solution of sal ammoniac (chloride of ammonium,) it undergoes a 
prodigious increase of bulk, increasing sometimes from one volume to two 
hundred volumes, without becoming in the least degree vesicular, and acquires 
a butyraceous consistence, while its metallic lustre is not impaired. A small ad- 
dition is at the same time made to weight, estimated at from 1 part in 2000 to 
1 in 10,000, and which certainly consists of ammonia and hydrogen in the pro- 
portions of ammonium. The sodium, it is supposed, combines with the chlorine 
of chloride of ammonium, and the liberated ammonium with mercury, so that 
the metallic product is an amalgam of ammonium. It speedily resolves itself 
again spontaneously into running mercury, ammonia and hydrogen. But the 
change which occurs to the mercury in this experiment is of a recondite nature, 
and admits of, at least, one other hypothetical explanation which is equally pro- 
bable. After all, however, neither isolation nor the metallic character is essen- 
tial to ammonium as an alkaline radical, other basyles being now admitted, such 
as ethyle and benzoyle, which have no claim to such characters.* 

Other classes of ammoniacal salts may be formed in which the fourth atom 
of hydrogen in ammonium is replaced by a metal of the magnesian family, and 
by copper in particular which most resembles hydrogen. Thus anhydrous 
chloride of copper absorbs an atom of ammonia with great avidity, which can- 
not afterwards be separated from it by the agency of heat. The compound is 
strictly analogous to chloride of ammonium, but contains an atom of copper in 
the place of hydrogen. Its formula is NH 3 Cu, CI, and it may be named the 
chloride of cuprammonium. This salt and many others are likewise capable 
of combining with more ammonia, which is retained less strongly, and has the 
relation of constitutional water to the salt. The constitution of these combi- 
nations will be more minutely considered in another part of the work. 



* Viewed in relation with the organic basyles, it might be termed ammonyle, rather than 
ammonium. 



144 ARRANGEMENT OF THE ELEMENTS IN COMPOUNDS. 

Amidogen and amides. The existence of another compound of nitrogen and 
hydrogen, containing an atom less of hydrogen than ammonia, (NH,,) is recog- 
nised in an important series of saline compounds, although it has not been iso- 
lated. These compounds are called amides, and hence the name amidogen ap- 
plied to their radical. When potassium is heated in ammoniacal gas, the metal 
is converted into a fusible green matter, which appears to contain the amide of 
potassium, while an atomic proportion of hydrogen is disengaged. Amidogen 
exists also in the white precipitate of mercury of pharmacy, formed on adding 
ammonia to corrosive sublimate, the product being a double chloride and amide 
of mercury (Hg Cl+Hg NH 2 .) 

Amides are produced in an interesting way, by the abstraction of the elements 
of water from compounds of ammonia with oxygen acids. Thus, on decompo- 
sing oxalate of ammonia by heat, the acid losing a proportion of oxygen, and the 
ammonia a proportion of hydrogen, oxamide sublimes, which consists of NH 2 -f 
2CO. When ammoniacal gas and anhydrous sulphuric acid vapour are mixed 
together, a saline substance is produced which dissolves in water, but is not sul- 
phate of ammonia, the solution affording no indications of sulphuric acid. It is 
believed to be a hydrated sulphamide, or to be constituted thus, NH 2 , S0 2 -f HO; 
a compound which it will be observed contains neither ammonia nor sulphuric 
acid. Similar products result from the action of ammonia on dry carbonic acid, 
and all the other anhydrous oxygen acids. The difference between these com- 
pounds and the true salts of ammonia affords a strong argument in favour of 
the ammonium theory of the latter. 

The other speculative view of the constitution of the ammoniacal amalgam, 
to which allusion has been made, is suggested by the remarkable and apparently 
peculiar aptitude of mercury to combine with amidogen, and by the position 
which hydrogen holds among elementary bodies, which is that of a metal of the 
magnesian class. It is, that the light ammoniacal amalgam is an amalgam of 
hydrogen, with the amide of mercury, or perhaps a double amide of mercury 
and chloride of sodium, diffused through it. The reaction by which these bodies 
may be produced, is explained in the following diagram : 

Before decomposition. After decomposition. 

f Mercury. • ~7 Amalgam of hydrogen 

Amalgam of J Mercury.' . ~/j Amid of mercury 

sodium. 1 Mercury. . /// Amalgam of hydrogen 

L Sodium. 

f Hydrogen 
Hydrochlorate J Amidogen 
of Ammonia. j Hydrogen / 

L Chlorine . ^ Chloride of sodium. 

Theory of the Ethers. As the ideas of chemists respecting salt-radicals first 
derived from certain simple bodies, such as chlorine, were afterwards extended 
through cyanogen, which so closely resembles them, to compound salt-radicals 
of greater complexity, so their ideas of basyles derived from the simple metals, 
have been extended through ammonium, which exhibits an absolute parallelism 
to potassium, to other compound basyles, the oxides and salts of which exhibit 
a less obvious relation to their metallic prototypes. In the theory of ether, first 
suggested by Berzelius, which was powerfully advocated by Liebig, and is now 
generally acquiesced in by chemists, that body is represented as the oxide of a 
basyle named ethyle, or as C 4 H 5 , O; and is considered itself a true base capa- 
ble of neutralizing acids, notwithstanding its want of alkalinity to the taste, or 




CHEMICAL AFFINITY. 145 

as tried by test-paper, although it is sapid and soluble in water. Alcohol, from 
the decomposition of which ether is derived, is the hydrate of the oxide of ethyle, 
C 4 H 5 0, HO; nitrous ether is the nitrate of ether, C 4 H 5 0, N0 3 ; oxalic ether, 
the oxalate of ether, C 4 H 5 0, C 2 J and sulphovinic acid may be called either 
the bisulphate of ether, or the sulphate of water and ether, HO, S0 3 -fC 4 H 5 
O, S0 3 . Hydrochloric ether is the chloride of ethyle, C 4 H 3 ,C1. The same 
views are extended to all the compounds of ether with both oxygen and hydro- 
gen acids. 

Another class of saline compounds has been derived from wood-spirit, of 
which the basyle is methyl 'e, C 2 H^O, equally numerous, and closely analo- 
gous in properties to the alcoholic series. Many other classes of organic 
compounds besides are found to correspond with that series, and the order of 
saline compounds is likely to undergo a vast expansion. It thus appears that 
conclusions respecting salts are of a wide and general application. Indeed the 
great question respecting the construction of an oxygen-acid salt, is the pivot 
upon which the whole body of chemical theory turns at this moment. 

SECTION II. 

CHEMICAL AFFINITY. 

In the preceding section, compound bodies have been viewed as already 
formed, and existing in a state of rest. The arrangement, weights and other 
properties of their atoms, have also been examined, with the relations and clas- 
sification of the compounds themselves. But chemistry is more than a des- 
criptive science; for it embraces, in addition to views of composition, the con- 
sideration of the action of bodies upon each other which leads to the formation 
and destruction of compounds. Certain bodies, when placed in contact, ex- 
hibit a proneness to combine with each other, or to undergo decomposition, 
while others may be mixed most intimately without change. The actual phe- 
nomena of combination suggest the idea of peculiar attachments and aversions 
subsisting between different bodies, and it was in this figurative sense that the 
term affinity was first applied by Boerhaave to a property of matter. A spe- 
cific attraction between different kinds of matter must be admitted as the cause 
of combination, and this attraction may be conveniently distinguished as che- 
mical affinity. 

The particles of a body in the solid or liquid state exhibit an attraction for 
each other, which is the force of cohesion, and even different kinds of matter 
have often an attraction for each other, which is probably of the same nature, 
although distinguished as adhesion. This force retains bodies in contact, which 
are once placed in sufficient proximity to each other. It is exhibited in the ad- 
hesion of two smooth pieces of lead pressed together, or perfectly flat pieces 
of plate-glass, which sometimes cannot again be separated. The action of 
glue, wax, mortar and other cements in attaching bodies together, depends 
entirely upon the same force. In detaching glue from the surface of glass, the 
latter is sometimes injured, and portions of it are torn off by the glue, the ad- 
hesive attraction of the two bodies being greater than the cohesion of the glass. 
The property of water to adhere to solid surfaces and wet them, its imbibition 
by a sponge, the ascent of liquids in narrow tubes and other phenomena of ca- 
pillary attraction, and the rapid diffusion of a drop of oil over the surface of 
water are illustrations of the same attraction between a liquid and a solid, and 
between different liquids. But this kind of attraction is deficient in a character 
which is never absent in true chemical affinitv — it affects no change in the 
13 



146 CHEMICAL AFFINITY. 

properties of bodies. It may bind different kinds of matter togethei, but it 
does not alter their nature. 

The tendency of different gases to diffuse through each other till a uniform 
mixture is formed, is another property of matter, the effect of a force wholly 
independent of chemical affinity. It is certain that this physical property is 
not lost in liquids, and that it contributes to that equable diffusion of a salt 
through a menstruum which occurs spontaneously, and without agitation to 
promote it.* 

Solution. The attraction between salt and water, which occasions the solu- 
tion of the former, differs in several circumstances from the affinity which 
leads to the production of definite chemical compounds. In solution, combi- 
nation takes place in indefinite proportions, a certain quantity of common salt 
dissolving in, or combining with any quantity of water however large; while 
a certain quantity of water, such as 100 parts can dissolve any quantity of that 
salt less than 37 parts, the proportion which saturates it. Water has a con- 
stant solvent power for every other soluble salt, but the maximum pro- 
portion of salt dissolved, or the saturating quantity, has no relation to the 
atomic weight of the salt, and indeed varies exceedingly with the temperature 
of the solvent. The limit to the solubility of a salt seems to be immediately 
occasioned by its cohesion. Water, in proportion as it takes up salt, has its 
power to disintegrate and dissolve more of the soluble body gradually dimi- 
nished, it dissolves the last portions slowly and with difficulty, and at last when 
saturated is incapable of overcoming the cohesion of more salt that may be 
added to it. The solubility in water of another body in the liquid state is not 
restrained by cohesion, and is in general unlimited. Thus alcohol, and also 
soluble salts above the temperature at which they liquefy in their water of 
crystallization, dissolve in water in any proportion. Generally speaking also 
those salts dissolve in largest quantity which are most fusible, or of which the 
cohesion is most easily overcome by heat, as the hydrated salts, and among 
anhydrous salts, the nitrates, chlorates, chlorides and iodides which are all re- 
markable for their fusibility. In this species of combination, bodies are not 
materially altered in properties, indeed are little affected except in their cohe- 
sion. 

The union also between a body and its solvent differs in a marked manner 
from proper chemical combination in the relation of the bodies to each other 
which exhibit it. Bodies combine chemically with so much the more force as 
their properties are more opposed, but they dissolve the more readily in each 
other, the more similar their properties. Thus metals combine with non-me- 
tallic bodies, acids with alkalies; but to dissolve a metal, another metal must 
be used, such as mercury; oxidated bodies dissolve in oxidated solvents as the 
salts and acids in water; while liquids which contain much hydrogen are the 
best solvents of hydrogenated bodies, an oil, for instance, of a fat or a resin, 
alcohol and ether dissolving the essential oils and most organic principles, but 
few salts of oxygen acids. The force which produces solution differs, there- 
fore, essentially from chemical affinity in being exerted between analogous 
particles, in preference to particles which are very unlike, and resembles more, 
in this respect, the attraction of cohesion. 

A more accurate idea of the varying solubility of a salt at different tempe- 
ratures may be conveyed by a curve constructed to represent it, than by any 
other means. The perpendicular lines in the following diagram, indicate the 



* Jerichau in Poggendorff 's Annalen, 34, 613; or Dove and Moser's Repcrtoriuin der 
Physik, 1,96. 1837. 



SOLUTION. 



147 



degrees of temperature which are marked below them, and the horizontal 
lines, quantities of salt dissolved by 100 parts of water. The proportion of 
any salt dissolved at a particular temperature may be learned by carrying the 
eye along the perpendicular line, expressing that temperature, till it cuts the 
curve of the salt, and then horizontally to the column of parts dissolved. 



SOLUBILITY OF SALTS IN 100 PARTS OF WATER. 



80 


















N % 


/ 




























































ril 


» ^ 
























&/ 














„« 


ji^> 








.' 


















<&/ 












,14 


*fi* 


'] 






_^ 


/. 
















x/ 










fep 


L L2S 






c 














S/r^±. 






y 


*"' 


' tf0«2 


|j£- 


ny 




o 


















>*r~ 


J^ 


jj!J*r 


K 






*40 




















r 1 


— h~- — yr '-.j 


-^ 


m 


— 












"CWon 


de of 


\'.. ', 


br| — 




rff-f- 


H 


*> 


i*q — 


< 30 


























w 


u* 


^ 




















\ 














o 


3 > 


f 










20 




1/ 


■4 


4" 




j» 
















Sii 


"L— — i 
-rrr: T^- 


— "ppiast 












a 


r^ 












1 








10 


y 






~ 



















































































































320 50O 68° 



104° 12-J3 140° 158° 176° 194° 212° 230° 



It will be observed that the perpendicular lines advance by 9 degrees, the 
first being 32°, and the last 230°. The solubility of nitrate of potash increases 
from 13 parts in 100 water at 32°, to 80 parts at 118°, or very rapidly with 
the temperature. Sulphate of soda is seen by the form of its curve to increase 
in solubility from 5 parts at 32° to 52 parts at 92°, but then to diminish in so- 
lubility with farther elevation of temperature. In this salt, sulphate of mag- 
nesia and chloride of barium the solubility is expressed in parts of the anhy- 
drous, and not the hydrated salt. The lines of chloride of barium and chlo- 
ride of potassium are parallel, showing a remarkable relation between the so- 
lubility of these two salts, which does not appear in any others. The line 
of chloride of sodium is observed to cut all the lines of temperature at the 
same height, 100 parts of water dissolving 37 parts of that salt at all tempera- 
tures. 

Chemical affinity acts only at insensible distances, and has no effect in caus- 
ing bodies to approach each other, which are not in contact, differing in this 
respect from the attraction of gravitation which acts at all distances, however 
great, although with a diminishing force. Hence, the closest approximation of 
unlike particles is necessary to develope their affinities, and produce combina- 
tion. Sulphur and copper in mass have no effect upon each other, but if both 
be in a state of great division, and rubbed together in a morter, a powerful af- 
finity is brought into play, the bodies themselves disappear, and sulphuret of 
copper is produced by their union, with the evolution of much heat. The af- 
finity of bodies is, therefore, promoted by everything which tends to their 
close approximation; in solids, by their pulverization and intermixture, this attrac- 
tion residing in the ultimate particles of bodies; in gases, by their spontaneous 
diffusion through each other, which occasions a more complete intermixture 
than is attainable by mechanical means; and between liquids, or between liquid 
and solid by the adhesive attraction which liquids possess, which must lead to 



148 CHEMICAL AFFINITY. 

perfect contact, and also by a disposition of liquid bodies to intermix, of the same 
physical character as gaseous diffusion. Elevation of temperature has certainly 
often a specific action in increasing the affinity of two bodies, but it also often 
acts by producing a perfect contact between them, from the fusion or vaporiza- 
tion of one or^both bodies. Hence, no practice is more general to promote 
the combination of bodies than to heat them together. 

If the affinity between two gases is sufficiently great to begin combination, the 
process is never interrupted, but is continued from the diffusion of the gases 
through each other till complete, or at least, till one of the gases is entirely con- 
sumed. Thus when hydrochloric acid and ammoniacal gases, in equal measures, 
are introduced into a jar containing at the same time a large quantity of air, the 
formation of hydrochlorate of ammonia proceeds, the gases appearing to search 
out each other, till no portion of uncombined gas remains. The combination 
of two liquids, or of a liquid and a solid, is also facilitated in the same manner 
by the mobility of the fluid, and proceeds without interruption, unless, perhaps, 
the product of the combination be solid, and by its formation interpose an ob- 
stacle to the contact of the combining bodies. But the affinities of two solids 
which are not volatile are rarely developed at al!, owing to the imperfection of 
contact. Even the action of very powerful affinities between a solid and a 
liquid or a gas, is often arrested in the outset from the physical condition of the 
former. Thus, the affinity between oxygen and lead is certainly considerable, 
for the metal is rapidly converted into a white oxide, when ground to powder, 
and agitated with water in its usual aerated condition; and in the state of extreme 
division in which lead is obtained by calcining its tartrate in a glass tube, the 
metal is a pyropiiorus, and combines with oxygen when cold with so much 
avidity as to take fire and burn the moment it is exposed to the air. Iron also, 
in the spongy and divided state in which it is procured by reducing the peroxide 
by means of hydrogen gas at a low red heat, absorbs oxygen with equal avidity 
at the temperature of the air, and takes fire and burns. But notwithstanding 
an affinity for oxygen of such intensity, these metals in mass oxidate very slowly 
in air, particularly lead, which is quickly tarnished indeed, but the thin coating 
of oxide formed, does not penetrate to a sensible depth in the course of several 
years. The suspension of the oxidation may be partly due to the comparatively 
small surface which a compact body exposes to air, and which becomes 
covered by a coat of oxide and protected from farther change ; but partly also 
to the effect of the conducting power of a considerable mass of metal in prevent- 
ing the elevation of temperature consequent upon the oxidation of its surface. 
For metals oxidate with increased facility at a high temperature, such as the 
lead pyrophorus quickly attains from the oxidation of the great surface which 
it exposes, compared with its weight. The heat from the oxidation of the su- 
perficial particles of the compact metal, however, is not accumulated, but carried 
off and dissipated by the conducting power of the contiguous particles, so that 
elevation of temperature is effectually repressed. It thus appears that the state 
of aggregation of a solid may oppose an insuperable bar to the action of a very 
powerful affinity. 

The affinity of two bodies, one or both of which are in the state of gas, is often 
promoted in an extraordinary manner by the contact of certain solid bodies. 
Thus oxygen and hydrogen gases may be mixed and retained for any length of 
time in that state without exhibiting any affinity for each other, and the gaseous 
mixture may, indeed, be heated in a glass vessel to any temperature short of 
redness, without showing any disposition to combine. But if a clean plate of 
platinum be introduced into the cold mixture, the gases in contact with the 
metallic surface instantly unite and form water ; other portions of the mixture 
come then in contact with the platinum and combine successively under its in- 
fluence, so that a large quantity of the gaseous mixture may be quickly united. 



ORDER OF AFFIMTY. 149 

The temperature of the platinum also rises from the heat evolved by the com- 
bination occurring at its surface, and the influence of the metal increasing with 
its temperature, combination proceeds at an accelerated rate, till the platinum 
becoming red hot, may cause the combination to extend to a distance from it, 
by kindling the gaseous mixture. Platinum acts in this manner with greatest 
energy, when in a highly divided state, as in the form of spongy platinum, owing 
to the greater surface exposed and the rapidity with which it is heated. The 
metal itself contributes no element to the water formed, and is in no respect 
altered. It is an action of the metallic surface, which must be perfectly clean, 
and is retarded, or altogether prevented by the presence of oily vapours and 
many other combustible gases, which soil the metallic surface. Mr. Faraday is 
disposed to refer the action to an adhesive attraction of the gases for the metal, 
under the influence of which they are condensed and their particles approxi- 
mated within the sphere of their mutual attraction so as to combine. This 
opinion is favoured by the circumstance, that the property is not peculiar to pla- 
tinum, but appears also in other metals, in charcoal, pounded glass, and all other 
solid bodies; although all of them, except the metals, act only when their tem- 
perature is above the boiling point of mercury. But on the other hand, at low 
temperatures, the property appears to be confined to a few metals only which 
resemble platinum in their chemical characters, namely in having little or no 
disposition to combine with oxygen gas, and in not undergoing oxidation in the 
air. The action of platinum may therefore be connected with its chemical pro- 
perties, although in a way which is quite unknown to us. The same metal 
disposes carbonic oxide gas to combine with oxygen, but much more slowly 
than hydrogen ; and it is remarkable that if the most minute quantity of carbonic 
oxide be mixed with hydrogen, the oxidation of the latter under the influence 
of the platinum is arrested, and not resumed till after the carbonic oxide has 
been slowly oxidated and consumed, which thus takes the precedence of the 
hydrogen in combining with oxygon. This extraordinary interference of a mi- 
nute quantity of carbonic oxide gas, which cannot from its nature be supposed 
to soil the surface of the platinum like a liquefiable vapour, seems to point to a 
chemical, perhaps to an electrical explanation of the action of the platinum, 
rather than to the adhesive attraction of the metal. The oxidation of alcohol at 
the temperature of the air, and also at a low red heat, is promoted in the same 
manner by contact with platinum. 

Order of affinity. The affinity between bodies appears to be of different 
degrees of intensity. Lead, for instance, has certainly a greater affinity than 
silver for oxygen, the oxide of the latter being easily decomposed when heated 
to redness, while the oxide of the former may be exposed to the most intense 
heat without losing a particle of oxygen. Again it may be inferred that potas- 
sium has a still greater affinity for oxygen than lead possesses; as we find the 
oxide of lead easily reduced to the metallic state when heated in contact with 
charcoal, while potash is decomposed in the same manner with great difficulty. 
But the order of affinity is often more strikingly exhibited in the decomposi- 
tion of a compound by another body. Thus sulphuretted hydrogen gas is 
decomposed by iodine, which combines with the hydrogen forming hydriodic 
acid, and liberates sulphur. The affinity of iodine for hydrogen is, therefore, 
greater than that of sulphur for the same body. But hydriodic acid is deprived 
of its hydrogen by bromine, and hydrobromic acid is formed; and this last is 
decomposed in its turn by chlorine, and hydrochloric acid produced. It thus 
appears that the order of the affinity of the elements mentioned for hydrogen 
is, chlorine, iodine, bromine, sulphur. The order of decompositions, in the 
precipitation of metals by each other from their saline solutions, also indicates 
the degree of affinity. Thus from the decomposition of the nitrates of the 
following metals, the order of their affinity for nitric acid and oxygen mar 

13* 



150 CHEMICAL AFFINITY. 

be inferred to be as follows: zinc, lead, copper, mercury, silver; zinc throwing 
down lead from the nitrate of lead, and all the other metab which follow it, 
lead throwing down copper; copper, mercury; and mercury silver; while 
nitrate of zinc itself is not affected by any other metal, and nitrate of silver is 
decomposed by all the metals enumerated. Bodies were first thus arranged 
according to the degree of their affinity for a particular substance, inferred from 
the order of their decompositions, by GeofTroy and Bergman, and tables of 
affinity constructed, of which the following is an example. Order of affinity 
of the alkalies and earths for sulphuric acid. 

Barytes 

Strontian 

Potash 

Soda 

Lime 

Magnesia 

Ammonia. 

Barytes is capable of taking sulphuric acid from strontian, potash, and every 
other base which follows it in the table, the experiment being made upon sul- 
phates of these bases dissolved in water; while sulphate of barytes is not de- 
composed by any other base. Lime separates ammonia and magnesia from 
sulphuric acid, but has no effect upon the sulphates of soda, potash, strontian, 
and barytes; and in the same manner any other base decomposes the sulphates 
of the bases below it in the column, but has no effect upon those above it. 
Tables of this kind when accurately constructed may convey much valuable 
information of a practical kind, but it is never to be forgotten that they are 
strictly tables of the order of decomposition and of the comparative force or 
order of affinity in one set of conditions only. This will appear by examining 
how far decomposition is affected by accessory circumstances in a few cases. 

Circumstances which affect the order of decomposition. Volatility in a 
body promotes its separation from others which are more fixed, and conse- 
quently facilitates the decomposition of compounds into which the volatile 
body enters. Hence, by the agency of heat, water is separated from hydrated 
salts; ammonia, from its combinations with a fixed acid, such a3 the phos- 
phoric; and a volatile acid from many of its salts, as sulphuric acid from the 
sulphate of iron, carbonic acid from the carbonate of lime, &c. Ammonia de- 
composes hydrochlorate of morphia at a low temperature, but on the other hand, 
morphia decomposes the hydrochlorate of ammonia at the boiling point of 
water, and liberates ammonia, owing to the volatility of that body. The fixed 
acids, such as the silicic and phosphoric disengage in the same way at a high 
temperature those acids which are generally reputed most powerful, and by 
which silicates and phosphates are decomposed with facility at a low tempe- 
rature. Many such cases might be adduced in which the order of decomposi- 
tion is reversed by a change of temperature. The volatility of one of its con- 
stituents must, therefore, be considered an element of instability in a com- 
pound. 

Decomposition from unequal volatility is, of course, checked by pressure, 
and promoted by its removal and by every thing which favours the escape of 
vapour, such as the presence of an atmosphere of a different sort into which 
the volatile constituent may evaporate. Carbonate of lime is decomposed 
easily at a red heat, provided a current of air or of steam is passing over it 
which may carry off the carbonic acid gas, but the decomposition ceases when 
the carbonate is surrounded by an atmosphere of its own gas; and the carbo- 
nate may even be heated to fusion, in the lower part of a crucible, without de- 
composition. Here the occurrence of decomposition depends entirely upon 
the existence of a foreign atmosphere into which' carbonic acid can diffuse. 



INFLUENCE OF INSOLUBILITY. 151 

Nitrates of alumina and peroxide of iron in solution, are decomposed by the 
spontaneous evaporation of their acid, even at the temperature of the air; and 
so is an alkaline bicarbonate when in solution, but not when dry. A change 
in the composition of the gaseous atmosphere may affect the order of decom- 
position as in the following cases: 

When steam is passed over iron at a red heat a portion of it is decomposed, 
oxide of iron being formed and hydrogen gas evolved. From this experiment 
it might be inferred that the affinity of iron for oxygen is greater than that of 
hydrogen. But let a stream of hydrogen gas be conducted over oxide of iron 
at the very same temperature, and water is formed, while the oxide of iron is 
reduced to the metallic state. Here the hydrogen appears to have the greater 
affinity for oxygen. But the result is obviously connected with the relative 
proportion between the hydrogen and steam which are at once in contact with 
the metal and its oxide at a red heat. When steam is in excess, water is de- 
composed, but when hydrogen is in excess, oxide of iron is decomposed; and 
why, because the excess of steam in the first case is an atmosphere into which 
hydrogen can diffuse, and the disengagement of that gas is therefore favoured; 
but in the second case the atmosphere is principally hydrogen, and represses 
the evolution of more hydrogen, but facilitates that of steam. The affinity 
of iron and hydrogen for oxygen at the temperature of the experiment, is so 
nearly balanced that the one affinity prevails over the other, according as there 
is a proper atmosphere into which the gaseous product of its action may dif- 
fuse. This affords an intelligible instance of the influence of mass or quantity 
of material, in promoting a chemical change; the steam or the hydrogen, as it 
preponderates, exerting a specific influence, in the capacity of a gaseous atmos- 
phere. 

The remarkable decomposition of alcohol by sulphuric acid, which affords 
ether, is another similar illustration of decomposition depending upon volatility, 
and affected by changes in the nature of the atmosphere into which evapora- 
tion takes place. Alcohol or the hydrate of ether is added in a gradual 
manner to sulphuric acid somewhat diluted, and heated to 280°. In these cir- 
cumstances, the double sulphate of ether and water is formed; water, which 
was previously combined as base to the acid, being displaced by ether, and 
evolved together with the water of the alcohol. The first effect of the reac- 
tion therefore, is the disengagement of watery vapour, and the creation of an 
atmosphere of that substance which tends to check its further evolution. But 
the existence of such an atmosphere offers a facility for the evaporation of 
ether, which accordingly escapes from combination with the acid and continues 
to be replaced by water, the affinity of sulphuric acid for water and for ether 
being nearly eqnal, till ether forms such a proportion of the gaseous atmos- 
phere as to check its own evolution, and to favour the evolution of watery va- 
pour. Then again alcohol is decomposed, and more of the double sulphate 
of water and ether formed as at first; the sulphate of ether of which comes 
in its turn to be decomposed as before, and ether evolved. Hence, both ether 
and water distil over in this process, the evolution of one of these bodies fa- 
vouring the separation and disengagement of the other. In this description, 
the evolution of water and ether are for the sake of perspicuity supposed to 
alternate, but it is evident that the result of such an action will be the simulta- 
neous evolution of the two vapours in a certain constant relation to each other. 
Influence of insolubility. The great proportion of chemical reactions which 
we witness are exhibited by bodies dissolved in water or some other men- 
struum, and are affected to a great extent by the relations of themselves and 
their products to their solvent. Thus carbonate of potash dissolved in water 
is decomposed by acetic acid, and carbonic acid evolved, the affinity of the 
acetic acid prevailing over that of the carbonic acid for potash. But if a stream 



152 CHEMICAL AFFINITY. 

of carbonic acid gas be sent through acetate of potash dissolved in alcohol, 
acetic acid is displaced; or the carbonic acid prevails, apparently from the in- 
solubility of the carbonate of potash in alcohol. The insolubility of a body 
appears to depend upon the cohesive attraction of its particles, and such de- 
compositions may therefore be ascribed to the prevalence of that force. 

It is remarkable that compounds are in general more easily formed by sub- 
stitution, than by the direct union of their constituents; indeed many com- 
pounds can be formed only in that manner. Carbonic acid is not absorbed by 
anhydrous lime, but readily by the hydrate of lime, the water of which is dis- 
placed in the formation of the carbonate. In the same manner, ether, although 
a strong base does not combine directly with acids, but the salts of ether are 
derived from its hydrate or alcohol,. by the substitution of an acid for the water 
of the alcohol. In all the cases, likewise in which hydrogen is evolved during 
the solution of a metal in a hydrated acid, a simple substitution of the metal 
for hydrogen occurs. 

Combination takes place with the greatest facility of all when double, decom- 
position can occur. Thus carbonate of lime is instantly formed and precipi- 
tated, when carbonate of soda is added to nitrate of lime, nitrate of soda being 
formed at the same time and remaining in solution. 

Before decomposition. After decomposition. 



Carbonate of 


C Soda. 


soda. 


1 Carbonic acid 


Nitrate of 


C Nitrate acid. 


lime. 


1 Lime. 




Nitrate of Soda. 



Carbonate of lime. 

Here a double substitution occurs, lime being substituted for soda in the carbo- 
nate, and soda for lime in the nitrate. Such reactions may therefore be truly 
described as double substitutions as well as double decompositions. They are 
most commonly observed on mixing two binary compounds or two salts. But 
reactions of the same nature may occur between compounds of a higher order, 
such as double salts, and new compounds be thus produced, which cannot be 
formed by the direct union of their constituents. Thus the two salts, sulphate 
of zinc and sulphate soda, when simply dissolved together, always crystallize 
apart and do not combine. But the double sulphate of zinc and soda is formed 
on mixing strong solutions of sulphate of zinc and bisulphate of soda, and se- 
parates by crystallization; the sulphate of water with constitutional water (hy- 
drated acid of sp. gr. 1.78) being produced at the same time and remaining in 
solution. The reaction which occurs may be thus expressed: 

Before decomposition. After decomposition. 

HO, S0 3 -f (NaO, S0 3 )> _ C HO, S0 3 -fHO 



i- 



ZnO, S0 3 -f (HO) S ~~ £ZnO, S0 3 -fNaO, S0 3 

in which the constituents of both salts before decomposition enclosed in brackets, 
are found to have exchanged places after decomposition, without any other 
change in the original salts.* The double sulphate of lime and soda can be formed 
artificially only in circumstances, which are somewhat similar. It is produced 
on adding sulphate of soda to acetate of lime, the sulphate of lime, as it then 
precipitates, carrying down sulphate of soda in the place of constitutional 
water (Liebig.) 

Different hydrates of the same body such as peroxide of tin, differ sensibly in 
properties, and afford different compounds with acids, unquestionably because 
these compounds are formed by substitution. The constant formation of phos- 
phates containing one, two or three atoms of base, on neutralizing the corres- 

* On water as a constituent of sulphates, Phil, Mag. 3d series, vol. VI. p. 417. 



FORMATION OF COMPOUNDS BY SUBSTITUTION. 153 

ponding hydrates of phosphoric acid with a fixed base, likewise illustrates in a 
striking manner the derivation of compounds, on this principle. Many insoluble 
substances, such as the earth silica, possess a larger proportion of water, when 
newly precipitated, than they retain afterwards, and in that high state of hy- 
dration they may exhibit affinities for certain bodies which do not appear in 
other circumstances. Hydrated silica dissolves in water at the moment of its 
separation from a caustic alkali; and alumina dissolves readily in ammonia, when 
produced in contact with that substance by the oxidation of aluminum. The 
unusual disposition to enter into combination which silica and alumina then 
exhibit is generally ascribed to their being in the nascent state, a body at the 
moment of its formation and liberation, in consequence of a decomposition, be- 
ing, it is supposed, in a favourable condition to enter anew into combination. But 
their degree of hydration in the nascent state may be the real cause of their su- 
perior aptitude to combine. 

Double decompositions take place without the great evolution of heat, which 
often accompanies the direct combination of two bodies, and with an apparent 
facility or absence of effort, as if the combinations were just balanced by the 
decompositions, which occur at the same time. It is perhaps from this cause 
that the result of double decomposition is so much affected by circumstances, 
particularly by the insolubility of one of the compounds. For it is a general law 
to which there is no exception, that two soluble salts cannot be mixed without 
the occurrence of decomposition, if one of the products that may be formed is 
as insoluble salt. On mixing carbonate of soda and nitrate of lime the 
decomposition seems to be determined entirely by the insolubility of the 
carbonate of lime which precipitates. When sulphate of soda and nitrate of 
potash are mixed, no visible change occurs, and it is doubtful whether the salts 
act upon each other, but if the mixed solution be concentrated, decomposition 
occurs and sulphate of potash separates by crystallization owing to its inferior 
solubility. 

It may sometimes be proved that double decomposition occurs on mixing 
soluble salts, although no precipitation supervenes. Thus on mixing strong so- 
lutions of sulphate of copper and chloride of sodium, the colour of the solution 
changes from blue to green, which indicates the formation of chloride of copper, 
and consequently that of sulphate of soda also. Now it is known that hydro- 
chloric acid will displace sulphuric acid from the sulphate of copper, at the tem- 
perature of the experiment, while sulphuric acid will on the other hand displace 
hydrochloric from chloride of sodium. It hence appears that in the preceding 
double decomposition, those acids and bases unite which have the strongest 
affinity for each other, and the same thing may happen on mixing other salts. 
But where the order of the affinities for each other of the acids and bases is un- 
known the occurrence of any change upon mixing salts, or the extent to which 
the change proceeds, is entirely matter of conjecture. 

It was the opinion of Berthollet, founded principally upon the phenomena of 
the double decompositions of salts, that decompositions are at all times depen- 
dent upon accidental circumstances, such as the volatility or insolubility of the 
product, and never result from the prevalence of certain affinities over others ; 
and consequently that in accounting for such changes, the consideration of affi- 
nity may be neglected. He supposed that when a portion of base is presented 
at once to two acids, it is divided equally between them, or in the proportion 
of the quantities of the two acids, and that one acid can come to possess the 
base exclusively, only when it forms a volatile or an insoluble compound with 
that body, and thereby withdraws it from the solution and from the influence 
of the other acid. His doctrine will be most easily explained by applying it to 
a particular case, and expressing it in the language of the atomic theory. The 
reaction between sulphuric acid and nitrate of potash is supposed to be as fol- 



154 CHEMICAL AFFINITY. 

lows. On mixing eight atoms of the acid with the same number of atoms of the 
salt, the latter immediately undergoes partial decomposition, its base being 
equally shared between the two acids which are present in equal quantities ; 
and a state of statical equilibrium is attained in which the bodies in contact 
are; 

(«) Four atoms sulphate of potash. 

Four atoms nitrate of potash. 

Four atoms sulphuric acid. 

Four atoms nitric acid. 
The nitrate of potash, it is supposed, is decomposed to the extent stated, and 
no farther, however long the contact is protracted. But let the whole of the 
free nitric acid now be removed by the application of heat to the mixture, and 
a second partition of the potash of the remaining nitrate of potash is the con- 
sequence; the free sulphuric acid decomposing the salt till the proportion of 
the two acids uncombined in the mixture is again equal, when a state of equi- 
librium is attained. The mixture then consists of: 

(b) Six atoms sulphate of potash. 
Two atoms nitrate of potash. 
Two atoms sulphuric acid. 
Two atoms nitric acid. 

On removing the free nitric acid as before, a third partition of the potash of 
the remaining nitrate of potash, between the two acids, on the same principle 
takes place, of which the result is: 

(c) Seven atoms sulphate of potash. 
One atom nitrate of potash. 
One atom of sulphuric acid. 
One atom nitric acid. 

The proportion of the two acids, free, being always the same. The repeated 
application of heat, by removing the free nitric acid, will cause the sulphuric 
to be again in excess, which will necessitate a new partition of the potash of 
the remaining nitrate of potash, till at last the entire separation of the nitric 
acid will be affected, and the fixed product of the decomposition be: 

(d) Eight atoms sulphate of potash. 

Here the affinity of the sulphuric and nitric acids, for potash is supposed to be 
equal; and the complete decomposition of the nitrate of potash by the former 
acid which takes place, is ascribed to the volatility of the latter acid, which, by 
occasioning its removal in proportion as it is liberated, causes the fixed sul- 
phuric acid to be ever in excess. 

Complete decompositions in which the precipitation of an insoluble sub- 
stance occurs, were explained by Berthollet in the same manner. On^dding 
a portion of barytes to sulphate of soda, the barytes decomposes the salt, and 
acquires sulphuric acid, till that acid is divided between the two bases in the 
proportion in which they are present, and, at this point, decomposition would 
cease, were it not that the whole sulphate of barytes formed, is removed by 
precipitation. But a new formation of that salt is the necessary consequence 
of that equable partition of the acid between the two bases in contact with it. 
which is the condition of equilibrium; and the new product precipitating, more 
and more of it is formed, till the sulphate of soda is entirely decomposed, and 
its sulphuric acid removed by an equivalent of barytes. 

According to*these views of Berthollet, no decomposition should be com- 
plete, unless the product be volatile or insoluble, as in the cases instanced. 
But such a conclusion is not consistent with observation, as it can be shown 
that a body may be separated completely from a compound, and supplanted by 
another body, although none of the products is removed by the operation 
of either of the causes specified, but all continue in solution and in contact 



DECOMPOSITION BY CONTACT. 155 

with each other. Thus the salt borax, which is a borate of soda, is entirely 
decomposed by the addition to its solution of a quantity of sulphuric acid, not 
more than equivalent to its soda, although the liberated boracic acid remains in 
solution; for the liquid imparts to blue litmus paper a purple or wine-red tint, 
which indicates free boracic acid, and not that characteristic red tint, resembling 
the red of the skin of the onion, which would inevitably be produced by the 
most minute quantity of the stronger acid, if free. But if the borax were only 
decomposed in part in these circumstances, and its soda equally divided be- 
tween the two acids, then free sulphuric, as well as boracic acid, should be 
found in the solution. The complete decomposition of the salt can be ac- 
counted for in no way but by ascribing it to the higher affinity of sulphuric 
acid for soda, than that of boracic acid for the same base. 

According to the same views, on mixing together two neutral salts containing 
different acids and bases, and which do not precipitate each other, each acid should 
combine with both bases, so as to occasion the formation of four salts. Again, four 
salts, of which the acids and bases are all dissimilar, should react upon each other in 
such a way as to produce sixteen salts, each acid acquiring a portion of the four 
bases ; and certain acids and bases, dissolved together in certain proportions, 
could have but one arrangement in which they would remain in equilibrio. 
Hence the salts in a mineral water would be ascertained by determining the 
acids and bases present, and supposing all the bases proportionally divided 
among the acids. But this conclusion is inconsistent with a fact observed in 
the preparation of factitious mineral waters, namely, that their taste depends 
not only on the nature of the . salts, but also upon the order in which they 
are added, (Dr. Struve of Dresden.) Before we can determine how the acids 
and bases are arranged in a mineral water, or what salts it contains, it may 
therefore be necessary to know the history of its formation. Instead of sup- 
posing the bases equally distributed among the acids in mixed saline solutions, it 
is now more generally assumed that the strongest base may be exclusively 
in possession of the strongest acid, and the weaker bases be united with the 
weaker acids, a mode of viewing their composition which agrees best with the 
medical qualities of mineral waters. It thus appears that the doctrines of Ber- 
thollet, by which the resulting actions between bodies in contact are made to 
depend upon their relative quantities or masses and the physical properties of 
the products of their combination, to the entire exclusion of the agency of proper 
affinities between the bodies in contact, cannot be admitted as a true represen- 
tation of the actual phenomena of combination. 



CATALYSIS, OR DECOMPOSITION BY CONTACT. 

An interesting class of decompositions has of late attracted considerable at- 
tention, which as they cannot be accounted for on the ordinary laws of chemical 
affinity, have been referred by Berzelius to a new power, or rather new form 
of the force of chemical affinity, which he has distinguished as the Catalytic 
for ce, and the effect of its action as Catalysis (from Kxtcc downwards, and Au#,I un- 
loosen.) A body in which this power resides, resolves others into new compounds, 
merely by contact with them, or by an action of presence, as it has been termed, 
without gaining or losing any thing itself. Thus an acid converts a solution of 
starch (at a certain temperature,) first into gum, and then into sugar of grapes 
although no combination takes place between the elements of the acid, and 
those of the starch, the acid being found free and undiminished in quantity, af- 
ter effecting the change. The same mutations are produced in a more remark- 
able manner by the presence of a minute quantity of a vegetable principle 
diastase, allied in its general properties to gluten, which appears in the germi- 



156 INDUCTIVE AFFINITY. 

nation of barley and other seeds, and converts their starch into sugar and gum, 
which being soluble, form the sap that rises into the germ, and nourishes the 
plant. This example of the action of a catalytic power in an organic secretion 
is probably not the only one in the animal and vegetable kingdoms, for it is not 
unlikely that it is by the action of such a force that very different substances are 
obtained from the same crude material by different organs. In animals this 
crude material, which is the blood, flows in the uninterrupted vessels, and gives 
rise to all the different secretions ; such as milk, bile, urine, &c, without the 
presence of any foreign body which could form new combinations. A beauti- 
ful instance of an action of catalysis has been traced by Liebig and Wchler in 
the chemical changes which the bitter almond exhibits. The application of heat 
and water to the almond, by giving solubility to its emulsin or albuminous 
principle, enables it to act upon an associated principle, amygdalin, of a neutral 
character, which then furnishes bodies so unlike itself as the volatile oil of 
almonds, and the hydrocyanic, oxalic and formic acids. The action of yeast 
in fermentation is a more familiar illustration of a similar power. The presence 
of that substance, although insoluble, is sufficient to cause the resolution of 
sugar into carbonic acid gas and alcohol, a decomposition which can be effected 
by no other known means. Changes of this kind, although most frequent in 
organic compounds, are not confined to them. The peroxide of hydrogen, 
discovered by Thenard, is a body of which the elements are held together by a 
very slight affinity. It is not decomposed by acids, but alkalies give its elements 
a tendency to separate, slow effervescence occurring with the disengagement of 
oxygen and water being formed. Nor do soluble substances alone produce this 
effect ; other organic and inorganic bodies, also, such as manganese, silver, 
platinum, gold, fibrin, &c, which are perfectly insoluble, exert a similar power. 
The decomposition in these instances, takes place by the mere presence of the 
foreign body, and without the smallest quantity of it entering into the new com- 
pound, for the most minute researches have failed in discovering the slightest 
alteration in the foreign body itself. The liquid persulphuret of hydrogen, and 
a solution of the nitrosulphate of ammonia of Pelouze are decomposed in the 
same way, and by contact of nearly all the substances which act upon peroxide 
of hydrogen. One remarkable difference indeed is observable, namely, that 
alkalies impart stability to nitrosulphate of ammonia, while acids decompose it, 
or the reverse of what happens with both the peroxide and persulphuret of hy- 
drogen* 

The phenomena referred to catalysis are of a recondite nature and much 
in need of elucidation. The influence of platinum, formerly noticed, in dis- 
posing hydrogen and oxygen to unite, is probably connected with the catalytic 
power of the same metal, but is at present equally inexplicable. It would be 
unphilosophical to rest satisfied by referring such phenomena to a force, of 
the existence of which we have no evidence. The doctrine of catalysis must 
be viewed in no other light than as a convenient fiction, by which we are en- 
abled to class together a number of decompositions not provided for in the 
theory of chemical affinity as at present understood, but which, it is to be ex- 
pected, will receive their explanation from new investigations. It is a provi- 
sional hypothesis, like the doctrine of isomerism, for which the occasion will 
cease as the science advances. 



INDUCTIVE AFFINITY. 
When a plate of zinc is plunged into hydrochloric acid, a chemical change 
* Phil. Mag. 3rd Series, vol. 10, p. 489. 



INDUCTIVE AFFINITY. 



157 



of a simple nature ensues, the metal dissolves combining with the chlorine of 
the acid and displacing its hydrogen, the gas-bubbles of which form upon the 
zinc plate, increase in size, detach themselves, and rise through the liquor to 
its surface. The solution of zinc, when effected by its substitution for hydro- 
gen, as in this experiment, is attended by a train of extraordinary phenomena, 
which become apparent when a second metal, such as copper, silver, or pla- 
tinum is placed in the same acid fluid, and allowed to touch the zinc, the se- 
cond metal being one upon which the fluid exerts no solvent action, or a less 
action than upon zinc. 

The zinc plate being connected by a metallic wire with a copper plate, as 
represented in the figure, and both dipped together Fig. 40. 

in the hydrochloric acid, the zinc only is acted upon, 
and dissolves as rapidly as before; but much of the 
hydrogen gas now appears upon, and is discharged 
from the surface of the copper plate, and not from 
the zinc. The hydrogen, being produced by the 
solution of the zinc, thus appears to travel through 
the liquid from that metal to the copper. But no 
current or movement in the liquid is perceptible, 
nor any phenomenon whatever to indicate the actual 
passage of matter through the liquid in that direc- 
tion. The transference of the hydrogen must take 
place by the propagation of a decomposition through 
a chain of particles of hydrochloric acid extending from the zinc to the copper, 
and may be conceived by the diagram on the margin, in, which each pair of 
associated circles marked cl and h represents a particle $f hydrochloric acid. 



zinc m 




copper 



Fig. 41. 




copper 



The chlorine cl of particle 1 in contact 

with the zinc combining with that metal, 

its hydrogen h combines, the moment it 

is set free, with the chlorine of particle 

2, as indicated by the connecting bracket 

below, and liberates the hydrogen of 

that particle, which hydrogen forthwith 

combines with the chlorine of particle 3, 

and so on through a series of particles of 

any extent till the decomposition reaches 

the copperplate, when the last liberated 

atom of hydrogen (that of particle 3in the (liagram)not having hydrochloric acid 

to act upon, is evolved and rises as gas in contact with the copper plate. 

It is to be observed that this succession of decompositions and recombina- 
tions leading to" the discharge of the hydrogen at the copper, does not occur 
at all unless that plate be in metallic connexion with the zinc, by means of a 
wire as in the figure, or by the plates themselves touching without or within 
the acid fluid. This would seem to indicate that while the decomposition 
travels from the zinc to the copper through the acid, some force or influence is 
propagated at the same time through the wire, from the copper back again to 
the zinc. That something does pass through the wire in these circumstances 
is proved by its being heated, and by its temporary assumption of certain elec- 
trical and magnetic properties. Whether any thing material does pass, or it 
is merely a vibration or vibratory impulse, or a certain induced condition that 
is propagated through the molecules of the wire, of which the electrical ap- 
pearances are the effects, cannot be determined with certainty. But a power 
to effect decomposition, the same in kind as that occurring in the acid jar, and 
which acts in the same sense or direction, is propagated through the wire, and 
appears to be fundamental to all the other phenomena. 
14 



158 



INDUCTIVE AFFINITY. 




Fig. 42. Let the wire, supposed to be of platinum, 

connecting the zinc and copper plates, be di- 
vided in the middle, and the extremities A 
and B of the portions attached to the copper 
and zinc plates respectively be flattened into 
small plates, and then dipped at a little dis- 
tance from each other in a second vessel con- 
taining hydriodic acid. Iodine will soon ap- 
pear at A, although that element is incapable 
of combining with the substance of the pla- 
tinum, and hydrogen gas will appear at B. 
If the connecting wire and the small plates A 
and B were of zinc or of copper, the hydrio- 
dic acid would be decomposed precisely in 
the same manner, but the iodine as it reached 
A would unite with the metal and form an iodide. Supposing a decomposing 
force to have originated in the zinc plate, and to have circulated through the 
hydrochloric acid in the jar to the copper plate, and onwards through the wires 
and the hydriodic acid back to the zinc, as indicated by the direction of the ar- 
rows, then the hydrogen of the hydriodic acid has followed the same course, 
and been discharged against the metallic surface to which the arrow points. 

The solution of the zinc in hydrochloric acid which developes these powers, 
acting at a distance, is not itself impeded, but on the contrary, is promoted by 
exerting such an influence. For placed alone in the acid, that metal scarcely 
dissolves at all, if pure and uncontaminated with other metals, or if its surface 
has been silvered with mercury, but it dissolves with rapidity when a copper 
plate is associated with it in the same jar, in the manner described. Hence the 
decomposing power which appears between A and B, cannot be viewed as ac- 
tually a portion of that which causes the solution of the zinc in the hydrochloric 
acid, for that force has suffered no diminution in its own proper sphere of 
action. 

This combination of metals and fluids is known as the simple voltaic circle. 
To explain the phenomena of the voltaic circle, the existence of a substantial 
principle, the electric fluid, has been assumed, of such a nature that it is readily 
communicable to matter, and capable of circulating through the voltaic arrange- 
ment, carrying with it peculiar attractive and repulsive forces which occasion 
the decompositions observed. A vehicle was thus created for the chemical af- 
finity which is found to circulate. But it is generally allowed that this form of 
the electrical hypothesis has not received support from observations of a recent 
date, particularly from the great discoveries of Mr. Faraday, which have com- 
pletely altered the aspect of this department of science, and suggest a very dif- 
ferent interpretation of the phenomena. • All electrical phenomena whatever are 
found to involve the presence of matter, or there is no evidence of the indepen- 
dent existence of electricity apart from matter, so that these phenomena may 
really be exhibitions of the inherent properties of matter. The idea of any thing 
like a circulation of electricity through the voltaic circle appears to be aban- 
doned. Electrical induction, by which certain forces are propagated to a dis- 
tance, is found to be always an action of contiguous particles upon each other, 
in which it is unnecessary to suppose that any thing passes from particle to 
particle, or is taken from one particle and added to another. The change which 
a particle undergoes, takes place within itself, and it is looked upon as a tem- 
porary development of different powers in different points of the same particle. 
The doctrine of polarity has thus come to be introduced into the discussion of 
electrical phenomena* 



* For Mr. Faraday's more recent views, the Eleventh and subsequent series of his Re- 



INDUCTIVE AFFINITY. 



159 



One reason for retaining the theory of an electric fluid or fluids, is that it 
affords the means of expressing in distinct terms those strictly physical laws, 
which are reputed electrical; and for many purposes such an hypothesis is un- 
questionably useful, if not absolutely necessary; but it has nothing to recom- 
mend it in the description of the chemical phenomena of the voltaic circle. 
These admit of a perfectly intelligible statement, when viewed as an exhibi- 
tion of ordinary chemical affinity, acting in particular circumstances, without 
any electrical hypothesis. It is often said that chemical affinity acts only at 
insensible distances, and this may be true of its direct action, but is not in- 
consistent with its exerting an influence at a distance, like many other forces, 
by an inductive agency, a mode of action which requires careful considera- 
tion. 

Magnetical polarity.— The ideas of induction and polarity, which now play 
so important a part 'in physical theories, were originally suggested by the 
phenomena of magnetism, which still afford the best illustrations of them. 
A bar magnet exhibits attractive power which is not possessed in an equal de- 
gree by every particle composing the bar, but is chiefly localized in two points 
at or near its extremities. The powers, too, residing at these points are not 
one and the same, or similar, but different, indeed contrary in their nature; 
and are distinguished by the different names of Boreal magnetism and Austral 
magnetism. The opposition in the mode of action of these powers is so per- 
fect, that they completely negative or neutralize each other when residing in 
the same particle of matter in equal quantity or degree, as they are supposed 
really to exist in iron before it is magnetized; and they only signalize their 
presence when displaced and separated to a distance from each other, as they 
are in a magnet. A body possessing any such powers residing in it, which 
are not general, but local, and not the same, but opposite, is said (in the most 
general sense) to possess polarity. 

In the theory of magnetism, it is found necessary to consider a magnet as 
composed of minute, indivisi- Fig. 43. 

ble particles or filaments of > M 

iron, each of which has indivi- 5 
dually the properties ofasepa- i. 
rate magnet. The displace- 1 
ment or separation of the two ? 
attractive powers takes place only within these small particles, which are 
called the magnetic elements, and must be supposed so mi- 
nute, that they may be the ultimate particles or atoms them- 
selves of the iron. A magnetic bar may therefore be repre- 
sented (as in the figure) as composed of minute portions, the 
right hand extremities of each of which possess one species 
of magnetism, and the left hand extremities the other. The 
shaded ends being supposed to possess boreal, and the light 
ends austral magnetism, then the ends of the bar itself, of which 
these sides of the elementary magnets form the faces, possess 
respectively boreal and austral magnetism, and are the boreal 
and austral poles of the magnet. Such, then, is the polarized 
condition of a bar of iron possessing magnetism, of which the 
attractive and repulsive powers residing at the extremities are 
the results. Of the existence of such a structure, the break- 
searches in the Philosophical Transactions for 1836, and the following years, may be re- 
ferred to. He has lately favoured the scientific world with a reprint of the whole series : 
Faraday's Experimental Researches in Electricity, R. and J. E. Taylor, London, 1839. 
The subject is also systematically treated by Professor Daniell in his recent work, An In- 
troduction to the Study of Chemical Philosophy, which may be consulted with advantage. 





160 



INDUCTIVE AFFINITY. 



ing of a magnet into two or more parts affords a proof, for it forms as many 
complete magnets as there are parts, new poles appearing at all the fractured 
extremities. 

Magnetical induction. — When to the boreal pole B of a magnet (Fig. 44.,) 
which may be of the horse-shoe form, a piece of soft iron a 6, wholly desti- 
tute of magnetic powers, is presented, a similar displacement of the magne- 
tic forces of its elements occurs as in the magnet itself; or a b becomes a mag- 
net by induction, and may attract and induce magnetism in a second bar a' b'; 
both of which continue magnetic so long as the first remains in the same posi- 
tion, and under the influence of A B. These induced magnets must have the 
same polarized molecular structure as the original magnet, but their magnetism 
is only temporary, and is immediately lost when they are removed from the 
permanent magnet. The displacement of the magnetisms in these induced 
magnets commences at the extremity a of a b, in contact with B, which ex- 
tremity has the opposite magnetism of B, (the different kinds of magnetism 
being mutually attractive,) and is the austral pole of a b; and b is its boreal 
pole. Of a' b' , again, the upper extremity a', in contact with 6', is the 
austral, and the lower extremity b', the boreal pole, or b b' have the same kind of 
magnetic power as the pole B of the original magnet, from which they are de- 
pendent. A third bar of soft iron placed at /; is likewise polarized, and the 
series of induced magnets may be still farther extended, but the attractive 
powers developed in the different members of the series, become less and less 
with their distance from the pole B of the original magnet. 



Fig. 45. 



Fig. 46. 




A 



B 





^ 




A 




B 
cu 


V 




7> 


a! 




V 


V a!' 



A similar set of bars may be connected with 
A (Fig. 45,) which become temporary magnets also 
according to the same law, the lower extremities 
of this set being austral. On now uniting the 
lower extremities of both sets by another bar of 
soft iron a" b", (Fig. 46,) either set renders a" b" 
a magnet, having its austral pole at a" and its bo- 
real pole at b" ; and acting together, they commu- 
nicate a degree of magnetism to the uniting bar, 
greater than either set possessed before they were 
united. By this connexion also the inductive ac- 
tions of each set of bars is brought to bear upon 
the other, and the attractive forces at all their 
poles are thereby greatly increased. In the most 
favourable conditions as to the size and connex- 
ion of the temporary magnets, with relation to the 
primary magnet, the former, however numerous, should each acquire powers equal 
to those of the original magnet. This general enhancement of power in the induced 
magnets, has been acquired by completing the circle of them between A and B. 
It is also important to observe, with a view to the future application of the re- 
mark, that a single bar of soft iron, or lifter, as b a, (Fig. 47,) connecting the poles 
Fig. 47. °^ a m &gnet A B, not only acquires at a and b equal, though op- 
posite powers to the contiguous poles of the magnet, but also re- 
acts by induction on these poles themselves, and increases their 
magnetism. The original magnetic forces of A and B are there- 
fore increased, by the opportunity to act inductively, which the 
connecting bar affords them. The threads of steel filings which 
are taken up by a magnet, (see figure 48) illustrate the inductive 
action of magnetism, for each grain of steel is a complete mag- 
net. It will be observed also that these threads diverge from 
each other ; because while unlike poles are in contact in each 
thread which attract, like poles are in contact of adjoining 



6 



INDUCTIVE AFFINITY. 161 

threads which repel. This re- Fig. 48. 

pulsion of polar chains by each 

other, there will be occasion . . .,, 

again to recur to. ,-,a: V; . , ll- 

Chemical polarity and in- ^ - jS\ 

duction. — With these elemen- ' ■ ! • ■ ■ '■ : 

taiy notions of polarity and the '■& ~~: j n ~ : - -- 

mode of action of a force by '% ; 

induction, we may return to '■##§ '„" 
the chemical phenomena of 

the voltaic circle. It is to be assumed that the zinc and hydrochloric acid are 
both composed of particles, or molecules, which are susceptible of a polarized 
condition, like the particles of soft iron, in which condition, the opposite ends of 
each molecule possess different and contrary attractive powers. Of hydrochlo- 
ric acid, the chemical atom may be taken as the polar molecule, and it will 
therefore consist of an atom of chlorine and an atom of hydrogen associated to- 
gether. The polar molecule of zinc may be supposed, for a reason which will 
afterwards appear, to consist of a pair likewise of associated atoms, which, how- 
ever, are in this body both of the same element. The powers developed in a 
polarized molecule of zinc and of hydrochloric acid are the same. One pole of 
each molecule has the attraction, or affinity, which is characteristic of zinc, or 
zincous attraction, and may be called the zincous pole ; while the other has the 
attraction or affinity, which is characteristic of chlorine, or chlorous attraction, 
and may be called the chlorous pole. Polarity is not an ordinary condition of 
the particles of either the zinc or acid, but is developed in both when brought 
into contact with each other. Such is to be supposed the mode in which che- 
mical affinity always acts. 

Zinc and acid in contact may therefore be represented (Fig. 49,) by trains of 
associated pairs of atoms. In the p IG# 49. 

molecule of hydrochloric acid B, Zinc. Acid, 

which is in contact with zinc, the // - N ^ N s-^r-\ /ivM ^-\ r~V~\ r7\T\ 
chlorous affinity is thereby deve- Us z kV Wfe) &^M L Z J { ^M) &<D 
loped on the side next the zinc, 1 E A B c d 

and we have there the constituent chlorine atom forming the chlorous pole, the 
fluidity of the acid allowing its molecule to take that position, which may be in- 
dicated by inscribing cl in the circle which represents the chlorine atom. The 
other atom of the particle B, or the hydrogen, comes therefore to be the seat of 
the opposite, or zincous pole, and is marked z. Of the two atoms fonning the 
polarizable molecule A of the zinc, the exterior atom which is in contact with 
the acid has thereby zincous attraction developed in it, and becomes the zincous 
pole, while the interior becomes the chlorous pole, as indicated in both by the in- 
scribed letters. This polar condition of the zinc and acid particles A and B must 
be supposed the necessary and immediate consequence of their simple contact. ' 

But each of these particles throws a train of particles of its own kind into a 
similar state of polarity ; A, the contiguous particles E and I of the zinc, and B 
the contiguous particles C and D of the acid. For cl of A becoming a chlorous 
pole, developes near it an opposite, or zincous poles in z of E, and a chlorous 
pole in c/, the more remote extremity of E ; in the same manner as the austral 
pole of a magnet developes, by induction, a boreal and austral pole in a piece 
of soft iron applied to it. And as the induced magnet, thus formed, will react 
upon a second piece of iron, and render it also magnetic, so the polarized par- 
ticle E, renders I similarly polar. The polarized condition of the particles C 
and D of the acid is produced by B in the same manner. But as in a series of 
induced magnets (Fig. 45.,) the magnetism acquired diminishes with the distance 
from the pole of the original magnet, so in trains of chemically polarized 

14* 



162 INDUCTIVE AFFINITY. 

molecules, such as A, E, I and B, C, D, the amount of polarity developed in each 
molecule will diminish with the distance from the sources of induction A andB; 
I being polarized to a less degree than E, and D than C. 

In the electrical theory of the voltaic circle as modified by Mr. Faraday, the 
zinc and hydrochloric acid are equally supposed to have a polarizable molecule. 
The polarity is also developed in these molecules by their approximation or con- 
tact. The molecule of hydrochloric acid is supposed to contain the positive and 
negative electricities which possess contrary powers, like the two magnetisms ; 
and are in combination and neutralize each other, in the non-polar condition of 
the molecule. But the contact of zinc causes the separation of the two elec- 
tricities in the acid molecule, its atom of chlorine next the zinc becoming nega- 
tive, and its atom of hydrogen positive. The electricities of the zinc molecule 
are separated at the same time, the side of the molecule next the acid becoming 
positive, and the distant side negative. The positive and negative sides of the 
two different molecules are thus^ in contact, the different electricities, like the 
different magnetisms, attracting each other. Hence, one side of each molecule 
is said to be positive instead of zincous, and the other side to be negative in- 
stead of chlorous. Polarity of the molecule is supposed in both views, but on 
one view the polar forces are the two electricities, on the other two chemical 
affinities. The difference between the two views is little more than nominal, for 
in both the same powers and properties are ascribed to the acting forces. The 
electricities are supposed to be the cause of the chemical affinities, but it may with 
equal justice be assumed that chemical affinities are the cause of the phenomena 
reputed electrical. One set of forces only is necessary for the explanation of the 
whole phenomena of combination, and the question is, whether are these forces 
electrical or chemical? Shall electricity supersede chemical affinity, or chemical 
affinity supersede electricity 1 If the electricities should be retained in discus- 
sing the voltaic circle, their names might be changed with some advantage, the 
positive be called zincous electricity, and the negative, chlorous electricity, which 
express (as will appear more clearly afterwards,) the nature of the chemical 
affinities with which these electricities are invested, and of which they are indeed 
constituted the sole depositaries. The propagation of the effects to a distance 
is supposed to take place by the polarization of chains of molecules, on the elec- 
trical as well as chemical theory of the voltaic circle, so that the explanations 
which follow, although expressed in the language of the chemical theory, are 
the same in substance as those which are given on the electrical theory as at 
present understood. 

If the attractions of the respective zincous and chlorous poles of A and B 
which are in contact, rise to a certain point, the atom z of A is detached from 
the mass of metal and combines with the atom cl of B, which last atom is dis- 
engaged at the same time from its hydrogen. Chloride of zinc is produced and 
dissolves in the acid liquid, while hydrogen is disengaged and rises from the 
surface of the metal ; or we have the ordinary circumstances of the solution of 
an isolated mass of zinc in hydrochloric acid. 



SIMPLE VOLTAIC CIRCLE. 

When the zinc is pure, or its surface amalgamated with mercury, the zinc- 
ous and chlorous attractions of the touching poles of A and B are not suffi- 
ciently intense to produce these effects, and combination does not occur. Let 
a copper plate F G H (Fig. 50.,) be then introduced into the acid, and connected 
by a metallic wire H K I with the zinc. The particles of the acid assume 
chlorous and zincous poles as before, so also do those of the zinc, and the 
chain of polarized molecules is now continued through the zinc and wire to 



SIMPLE VOLTAIC CIRCLE. 163 

the copper, the exterior particle F of which, it will be observed, comes thereby 
to present a chlorous pole to the acid. The contiguous particle D of acid is 

Fig. 50. 

Connecting wire. 




thus exposed to a second induction from the chlorous polarity of the copper, 
which increases the zincous polarity of the side of D next F, and therefore, 
co-operates in enhancing the polarized conditions already assumed by the chain 
of acid particles extending between the two metals. An endless chain or circle 
of polarized molecules symmetrically arranged is thus formed, such as exists 
in a magnet of which the poles are united by a lifter, in which every particle 
in the chain has its own polar condition elevated by induction, and at the same 
time does itself react upon and elevate the polar condition of every other par- 
ticle in the chain. The result of this is that the primary attraction of the zinc 
atom z of A, for the chlorine, cl of the hydrochloric acid B is increased, and 
attains that degree of intensity at which the resistance to the impending com- 
bination is overcome, and the z and cl of A and B unite. But in a circle of 
polar molecules, in which the condition of any one molecule determines and is 
determined by that of every other, the intensity of the polar condition is ne- 
cessarily the same in every element of the circle. The chemical polarity, 
therefore, of the other particles forming the chain must increase to an equal 
degree with A and B, when the circle is completed, and the same change must 
now occur in all of them that has occurred in A and B. The pole of B next 
C is intensely zincous, while that of C next B is intensely chlorous, whence 
the chlorine and hydrogen cl and z of these two particles combine together. 
At the same time and for the same reason, the hydrogen z of C unites with the 
chlorine cl of D; and so on, through a chain of particles of hydrochloric 
acid of any length, till the copper is reached, when the last acid particle, D in 
the figure, yields its hydrogen z to the chlorous pole of the copper cl. But 
the hydrogen, not being capable of combining with the copper, is liberated as 
gas upon the surface of that metal. 

Some internal change of a similar character appears to take place in the chain 
of polarized molecules extending through the metals themselves — a series of 
molecular detachments and re-attachments, among the atoms of their polar 
molecules, like the decompositions and recompositions in the acid, causing evolu- 
tion of heat and other phenomena, generally reputed electrical, which the zinc 
and copper plates and the connecting wire exhibit. 

The polar molecule of the metals has been assumed to contain two atoms 
(like that of the acid,) with the view of assimilating these intestinal changes 
in the solid to those occurring in the fluid portion of the voltaic circuit, and also 
because it appears to account for the advantage of amalgamating the zinc sur- 
face. In the amalgamated plate, it is not zinc itself, but a chemical combina- 
tion of mercury and zinc which is presented to the acid, in which mercury is 
the " negative" element, and which might, therefore, be called a hydrarguret 
of zinc. That combination likewise is fluid. It must constitute the polar 
molecule, which will then consist of an atom of mercury as chlorous pole, 
and an atom of zinc as zincous pole, and not of two atoms of zinc. These 



164 IDUCTIVE AFFINITY. 

metallic molecules are also capable of movement from their fluidity, and will, 
therefore, place themselves in forming a polar chain with their unlike poles 
together, as the fluid acid particles arrange themselves. So that in an amal- 
gam of zinc, of which A, E and I are polar molecules (Fig. 49.,) all the 
atoms marked cl are mercury, and those marked z are zinc. It thus fol- 
lows that, when by contact with an acid the amalgam is polarized, it pre- 
sents a face of zinc only to the acid. If the mercury were exposed to the 
acid, that metal would completely derange the result, acting locally like a cop- 
per plate, as will afterwards be explained. The previous combination of the 
zinc (with mercury,) likewise prevents that metal from yielding easily to the 
chlorine of hydrochloric acid; and the zinc of the amalgam is, therefore, not 
dissolved, till the affinities are enhanced by the introduction of a copper plate 
into the acid, and the formation of a voltaic circle. 

It would thus appear that zinc, associated with copper, dissolves more readily 
in the acid than when alone, because the attraction or affinity of the zinc for 
chlorine is increased by the completion of a circle of similarly polarized particles, 
in the same manner as the magnetic intensity at one of the poles of a magnet is 
increased on completing the circle of similarly polarized molecules, by connect- 
ing that pole by means of soft iron with the other pole (Fig. 46, page 160.) 

Although the terms of the electrical hypothesis are at present avoided, still it 
will be convenient to denominate the zinc, being the metal which dissolves in 
the acid, the active or "positive metal, and the copper, which does not dissolve 
the inactive or negative metal of the voltaic circle. 

Looking to the condition of the two connected metals in the acid, it will be 
observed that the surface of the zinc presented to the acid has zincous affinity, 
or is zinco-polar, but the surface of the copper presented to the acid has, on the 
contrary, chlorous affinity, or is chloro-polar. Such a condition of the copper is 
necessary to the propagation of the induction ; and the advantage of copper or 
platinum as the negative metal in a voltaic arrangement depends upon there 
being little or no impediment to either of these metals assuming the chlorous 
condition, that can arise from the peculiar affinity of the metals named for the 
chlorine of the acid ; an affinity which tends to cause them to be superficially 
zincous instead of chlorous. If the second metal were zinc, the surface of it 
would be disposed to dissolve in the acid, and becoming on that account zincous, 
would induce a polarization in the intermediate acid, in an opposite sense from 
that induced by the first plate of zinc ; which counter polarizing actions would 
mutually neutralize each other. The acid between the two zinc plates would 
be like a piece of iron connecting two like magnetic poles, which itself is not 
then polarized. 

But if one of the two zinc plates were less disposed to dissolve in the acid than 
the other, from the physical condition of its surface, from the acid being weaker 
there, or from any other cause, then the plate so situated might become negative 
to the other, and a voltaic circle of weak power be established, in which both 
metals were zinc. 

If zinc is alone in the acid, and every superficial particle of the metal equally 
disposed dissolve, then the zinc every where exposes a surface in a state of zinc- 
ous polarity ; and an inductive circle in the liquid, starting from one particle of 
the zinc and returning upon another, cannot be established, as this requires that 
a part of the zinc surface be chlorous. But if the zinc contains on its surface a 
single particle of copper, F (Fig. 51,) a chlorous pole is created upon which 
an inductive circle starting from an adjoining particle of zinc, A, and passing 
through the liquid, may return as shown in the figure. It is the formation of 
such circles that causes impure zinc, which is contaminated by other metals, to 
dissolve so much more quickly in an acid than the pure metal. Why such cir- 
cles are not formed when the positive metal in combination with the zinc is mer- 



COMPOUND VOLTAIC CIRCLE. 



165 



Fig. 51. 




cury, which forms a fluid alloy, has already been accounted 
for ; and the nature of the evil which might otherwise at- 
tend the amalgamation of the zinc is now evident. 

The whole chain polarized molecules in the voltaic circle 
admits of a natural division into two segments, the acid or 
liquid segment, BCD (Fig. 50,) and the metallic segment, 
A K F, each of which has a pair of poles, the unlike poles of 
the two segments being opposed to each other. The pole at 
B of the acid portion is chlorous, and is opposed to the zinc- 
ous pole at A of the metallic segment ; while the pole of the 
liquid segment at D is zincous, and is opposed to the chlo- 
rous pole of the metallic segment at F. The distribution 
of polarity in these two segments is, therefore, the same as 
in two magnets with their unlike or attracting poles in contact. 

Such, then, is the action of affinity by induction, which the mere introduction 
of zinc and copper in contact into the same acid liquid, is sufficient to develope, 
and which accounts for the discharge of the hydrogen upon the surface of the 
copper in such an arrangement, the remarkable phenomenon by a description 
of which this subject was introduced. 

It remains for us to apply the same principles to explain the additional pheno- 
mena of the second case described, in which the connecting wire, supposed to 
be of platinum, between the zinc and copper plates, is divided, and the broken 
extremities introduced into hydriodic acid (Fig. 42, page 158.) 

Broken at any point, as at K, (Fig. 50,) it is evident that if the polarized con- 
dition be still sustained, the portion of the metallic segment connected with the 
copper plate will terminate with a zincous pole at K, and that connected with 
the zinc, with a chlorous pole ; which may be indicated respectively by K and 
L in Fig. 52. When hydriodic acid is interposed between K and L, the breach 

Fig. 52. 




is repaired by the polarization of a chain of particles of that acid. The extre- 
mity K, being zincous induces chlorous polarity in the side of the hydriodic acid 
particle which it touches, in consequence of which the iodine atom (the analogue 
of chlorine) of the hydriodic acid molecule is presented to that pole, and liberated 
there when decomposition occurs. The extremity L of the zinc or positive metal 
element is chlorous, and therefore induces zincous polarity in the particle of hy- 
driodic acid which it touches, and hydrogen (the analogue of zinc) is liberated 
there. The polarity in an induced circle must necessarily be of equal intensity 
at every point in it, and being sufficient at A to cause the decomposition of the 
hydrochloric acid, must also decompose the hydriodic acid between K and L, 
otherwise it is never established at A, nor any where else. 

In the present arrangement, the voltaic circle is broken into four segments, or 
has four polarized elements, every terminal pole of which is in contact with a 



166 



INDUCTIVE AFFINITY. 



Zinc or 

positive 

metal 




metal 



pole of a different name ; and the whole arrangement may be compared to a 
circle of four magnets with the attractive poles in contact. 

Fig. 53. These elements are : — First, the zinc 

Fluid plate or positive metal, A L, of which 

the end at A, in the hydrochloric acid 
(Fig. 53,) has zincous affinity, and the 
end at L, in the hydriodic acid, chlo- 
rous affinity. 
Copper or Secondly, the body of hydrochloric 
negative acid, A F, between the zinc and cop- 
per plates, of which the surface at A, 
in contact with the positive metal, has 
chlorous, and that at F in contact with 
the negative metal, zincous affinity. 
Thirdly, the copper or negative 
metal F K, of which the end at F in the hydrochloric acid, has chlorous affinity, 
and at K, in the hydriodic acid, zincous affinity. 

And fourthly, the body of hydriodic acid, K L, between the zincous and chlo- 
rous poles of the negative and positive metals, of which the surface K, in contact 
with the negative metal, is chlorous, and the surface L, in contact with the po- 
sitive metal, zincous. 

In every voltaic circle employed to produce decomposition, these four elements 
are to be looked for. Hereafter, in adverting to any one of these elements it 
will be sufficient to confine our notice to its terminal polarities or affinities with- 
out recurring to the polarized condition of the element itself, upon which its ter- 
minal affinities depend. 



Fluid 



COMPOUND VOLTAIC CIRCLE. 

In both the arrangements described there is only one source of polarizing 
force, namely the action between the zinc and acid at A. But a circle of a si- 
milar nature may be constructed embracing within itself two or more of such 
primary sources of polarizing power, and the intensity of the polar condition of 
the whole circle be thereby greatly increased. 

Fig. 54. Fig. 54 represents such a circle in which there 

are two zinc plates, both supposed to be in con- 
tact with any hydrochloric acid, namely at A 
and at C, and a copper plate attached to each 
of these zincs. The circle is made up of two 
pairs of copper and zinc, copper and zinc, with 
acid between each pair. The polar condition 
of such a circle will easily be observed. By the 
contact of the acid and zinc at A, a zincous pole 
is established there in the first zinc plate, and a 
chlorous pole in the acid, which are so inscribed 
in the diagram. These occasion the formation of a chlorous pole at D in the 
first copper, the united zinc and copper A D forming together one polar element ; 
and a zincous pole at B in the acid, the column A B of acid, being the second 
polar element. The further effect of the induction is to produce a chlorous pole at 
B in the second copper, of which the corresponding zincous pole is at C, in the 
second zinc ; the united zinc and copper B C forming together a third polar ele- 
ment. And, as a last consequence of the inducing force originating at A the column 
of acid between C and D becomes a fourth polar element of the circle, having a 
chlorous pole at C and a zincous pole at D. Now it will be observed that the che- 




Ziml 



ZincZ 



top.Z 



COMPOUND VOLTAIC CIRCLE, 



167 



Fig. 55. 
Fluid 



mical affinity between the acid and zinc at C tends to produce the same polar 
conditions at that point, as are already established there from the effect of in- 
duction. The extremity of the zinc plate at C is in fact zincous both primarily 
and by induction ; and the acid in contact with it, likewise chlorous, both pri- 
marily and by induction ; and generally throughout the whole circle, the polar 
conditions determined by the second chemical action at C are the same as those 
determined by the first action at A. 

In the last arrangement, the inductive ac- 
tions are in the same direction, and favour 
each other ; but a circle may be constructed 
in which the inductions, being in opposite di- 
rections, oppose and neutralize each other. 
Thus if A D (Fig. 55.) be entirely zinc, both 
its extremities being exposed to acid, will tend 
equally to be zincous. In the same way if B Z ; nc 
C be entirely copper, the condition of both its 
extremities will be chlorous from the action 
of the acid on the two ends of the zinc ; and 
consequently the elements of such a circle 
could have no polarity. 




Copper 



Fluid 




Acid 



A circle is represented in Fig. 56, containing three sources of polarizing force. 
It consists of three alternations of copper and F r *56 

zinc symmetrically arranged, and forming three 
polar elements F A, B C and D E, with three 
acid columns between these alternations, which 
form three additional polar elements, A B, C D 
and E F. The number of alternations of copper 
and zinc, with acid, may obviously be increased 
to any extent, and the chemical action of the 
acid on the zinc in each alternation is found to 
increase in a marked manner up to the number 
of 10 or 12 alternations. This increase of the 
affinity is undoubtedly owing to the favouring 
inductive action, which the chemical actions at the different points have upon 
each other. Such a compound circle may be compared to a number of magnets 
disposed in a circle with their attracting pole.s together, of which each would 
have its magnetic intensity exalted by induction from all the rest. When such 
a circle is broken at any point, all chemical action and polarization cease till 
contact is again made, and the circuit completed. The polarization, too, being 
the result of a circular induction involving so many lines or -chains of particles, 
cannot, when once established, be more nor less at any one point in the circuit 
than at others. The resulting chemical action must therefore be every where 
equal in the circle, and consequently the same quantity of zinc be dissolved and 
hydrogen evolved in each acid. 

If any metallic element of this compound circle be broken, and a polarizable 
liquid be interposed between the metallic extremities so as to complete the cir- 
cuit, decomposition occurs in that liquid as in the simple interrupted circle (Fig. 
52.) The polarizing influence of the compound circle being of high intensity, 
more numerous and difficult decompositions are effected by means of it, than 
by the simple circle. The compound voltaic circle is indeed a decomposing 
instrument of great efficiency. 

If in this arrangement the position of one of the metals in the series be reversed, 
so that a zinc is where a copper should be, then by the action of the acid on 
that zinc polarization in the wrong direction is occasioned, which greatly di- 



168 



INDUCTIVE AFFINITY. 



minishes the general polarity of the circle, reducing it in an arrangement often 
alternations to one fourth according to Mr. Daniell. 

In the first of the two annexed diagrams (Fig. 57,) is represented a com- 

Fig. 57. 




pound circle, such as is employed to produce decomposition and called a voltaic 
battery, consisting of three acid jars, each of which contains a zinc and copper 
plate ; and which are termed active cells, as they are sources of polarizing 
power, from the action of acid upon zinc which takes place in them. 

In the second diagram (Fig. 58,) the same arrangement is repeated with the 

Fig. 58. 




addition of a third jar, termed the decomposing cell, which contains any polariza- 
ble liquid, with two platinum plates immersed in it. Each copper, it will be seen, 
is connected by a wire with the following zinc, and in the first diagram, the 
copper in the third cell C" is immediately connected with the zinc in the first 
cell Z by a wire, and the circuit thus completed. The polar elements in the 
circle of the first diagram, it will be found are six in number ; namely, the three 
acid columns between the metals in the cells, ab, cd, and ef; and the three pairs 
of zinc and copper plates, each of which forms a single polar element, of which 
the surface of the zinc is the zincous, and the surface of the copper, the chlo- 
rous pole. In the second diagram, one of these metallic elements Z C" is di- 
vided, and apolarizable liquid %h, in the cell of decomposition, interposed between 
the broken extremities PI and PI'. To ascertain the polar condition of the ex- 
tremities, or the terminal platinum plates in the decomposing cell, it is to be ob- 
served that PI' with Z forms one polar element, of which Z being a zincous 
pole, PI' must be a chlorous pole. Again PI with C" forms one polar element, 
of which C" being a chlorous pole, PI must be a zincous pole. Now the plati- 
num plates PI and PI' which are thus zincous and chlorous, are disposed in the 



THE SOLID ELEMENTS OF THE VOLTAIC CIRCLE. 169 

decomposing cell, in regard to one another, the first to the left, and the second 
to the right, as the zincous and chlorous plates, (the zinc and copper,) also 
are arranged in the active cells. It will be convenient to distinguish by names, 
the poles which these terminal platinum plates constitute, as they are much 
more frequently referred to, and of greater consequence than any other poles in 
voltaic battery, when used as an instrument of decomposition as it constantly is. 
The chlorous plate PI' which is in connexion with a zinc plate Z, may be called 
the chloroid (like chlorine, quasi-chlorine,) and the zincous plate PI which is con- 
nected with a copper plate C" may be called the zincoid, (like zinc, quasi-zinc,) 
names which express the virtual properties of each plate, or the particular at- 
tractive power and affinity which each of them acquires from its place in the 
circle. 

When hydrochloric acid is the polarizable liquid interposed between these 
plates, chlorine is of course attracted by the surface of the zincoid and discharged 
there, and hydrogen by the face of the chloride and discharged upon that plate. 
On the electrical hypothesis, the same plates are variously denominated : 

The zincoid as the positive pole, the positive electrode, the anode, and the 
zincode. 

The chloroid as the negative pole, the negative electrode, the cathode and the 
platinode. 

The cell of decomposition thus interpolated in the voltaic circle is an obsta- 
cle to induction, and reacts on the whole series, reducing the chemical action 
and evolution of hydrogen in each of the active cells by at least one-third. In 
that retarding cell itself, the amount of decomposition, is necessarily the same 
as in the other cells. Mr. Daniel! found the chemical action reduced to one- 
tenth, in a series of eight active and two such retarding cells ; and entirely 
stopped by three retarding to seven active cells. 



OF THE SOLID ELEMENTS OF THE VOLTAIC CIRCLE. 

The elements of a voltaic circle are obviously of two different kinds, the 
metals or solid portions, through the substance of which chemical induction is 
propagated without decomposition, and the liquids in the cells, which yield to 
the induction and suffer decomposition. In reference to the fiist, it is to be 
observed that, as only iron and one or two other metals of the same natural 
family are susceptible of magnetic polarity, so the susceptibility of chemical 
polarity which appears in the voltaic battery is not possessed by solids in ge- 
neral, but is confined to the class of bodies to which zinc belongs, — the metals, 
all of which possess it, with the addition of carbon in the form of charcoal, and 
the sulphuret of silver when heated. The non-metallic elements with their 
compounds, and the oxides, sulphurets and other compounds of the metals, 
some of which exhibit the metallic lustre, are all destitute of this power, and 
cannot, therefore, be used as solid elements of the circle. A body available 
for this purpose is termed a conductor on the electrical hypothesis, a name 
which may be retained as it is not at variance with the function assigned to 
the metals in the circle viewed as a chemico-polar arrangement. Two diffe- 
rent metals are combined in a circle, one of which is acted on by the liquid, and, 
therefore, called the active or the positive metal, while the other is not acted 
upon, and is, therefore, called the inactive or the negative metal; and it has al- 
ready been stated that the more easily acted on by the liquid or the more highly 
positive the one metal, and the less easily acted upon, or more negative the 
other metal, the more proper and efficacious is the combination. In the fol- 
lowing table several of the metals are arranged in the order in which they ap- 
pear positive or negative to each other, when acted on by the acid fluids com- 
15 



170 INDUCTIVE AFFINITY. 

monly employed in the voltaic battery. Each metal is positive to any one 
below it in the table, and negative to any one above it. 

Most positive. 

Potassium. 

Sodium. 

Manganese. 

Zinc. 

Cadmium. 

Iron. 

Nickel. 
. Cobalt. 

Lead. 

Tin. 
. Bismuth. 

Copper. 

Silver. 

Mercury. 

Palladium. 

Platinum. 

Rhodium. 

Iridium. 

Gold. 
Most negative* 

Zinc which stands high in the list, is the only metal which can be used with 
advantage in the voltaic battery, as the positive metal. Although closely ap- 
proaching zinc in the strength of its affinities, iron is ill adapted for the pur- 
pose, from the impossibility of amalgamating its surface, the irregularity of its 
structure, and certain peculiarities of this metal in reference to chemico-pola* 
rity. Platinum forms an excellent negative metal from the weakness of its 
affinities, and is generally used for the plates in the cell of decomposition. 
Silver also is highly negative, but copper is the only negative metal, which 
from its cheapness can be used in the construction of active cells of ordinary 
magnitude. 

But although the difference between two metals in point of affinity be very 
small, yet their association in the same acid always gives a decided predomi- 
nance to the affinity of the more positive, by causing the surface of the other 
to become chlorous, and therefore wholly inactive in an acid fluid. A negative 
metal may thus be protected from the solvent action of saline and acid liquids, 
by association with a more positive metal ; iron, for instance, by zinc, as in 
articles of galvanized iron, which are coated with the former metal; and cop- 
per by either zinc or iron, as was remarkably illustrated in the attempt made 
Fig. 59. °y ^ r H. Davy to defend the copper sheathing of ships 

from corrosion in sea-water, by means of his protec- 
- -^- tors. These were small masses of iron or zinc fixed 

^^^■■BPIIk upon the ship's copper, at different points under the 
/ Jjjjp^ i ""'^|||lk water line. They completely answered the purpose 
fBBf lK\ °f P r o tectm ? tne copper, but unfortunately gave rise 

fffi? ]U to a deposition of earthy matter upon that metal to 

fBL Jill which barnacles and sea-weeds attached themselves. 

^^bv ^Jjjjy and thereby diminished the facility of the ship's motion 

•^^^flBa^v" A weak galvanic circle may even be formed of a sin- 

gle positive metal in an acid, as the zinc A B (Fig. 
59,) provided the surfaces of the metal exposed to the acid at A and B are in 



LIQUID ELEMENTS OF THE VOLTAIC CIRCLE. 171 

different conditions as to purity or mechanical structure, and therefore un- 
equally acted upon by the acid; whereupon the part least disposed to dis- 
solve becomes negative to the other. A zinc plate may also be unequally 
acted on and thrown into a polar state, from the liquid in which it is im- 
mersed varying in composition and activity, at different points of the me- 
tallic surface. A circle may thus be formed of one metal A B with two liquids 
A E and E B, which merge into each other, and form together one polar ele- 
ment A B. 

The two metals in a circle have generally been exhibited in metallic con- 
tact, and forming together one polar element, but they may be separated, as 
are the zinc and copper plates A D and C B in the y\g. 60. 

diagram (Fig. 60,) by two polarizable fluids, pro- 
vided these fluids are such as a strong acid at A B, _ >*||j|l|j|^_ 
and as iodide of potassium at D C, the first of which ^g^^^^gl^ 
acts very powerfully on zinc, while the other acts very Jjjjf \ A 

feebly upon that metal (unless associated with cop- pHf \]\ 

per;) so that of the consequent opposing inductions, |Hj[i )•'■ j 

that originating at A greatly exceeds and overpowers lip, J I 

that from D. It is likewise necessary that the fluid ^pp^-g^g^t^/ 
D C be of easy decomposition, so as to yield to the ^^^HS^^ 8 
polarizing power of the single circle. In this ar- 
rangement, however, it is obvious that the zinc itself forms a complete po- 
lar element, of which A is the zincous, and D the chlorous pole; and the 
copper also an entire polar element of which B is the chlorous, and C the 
zincous pole. 

The preceding table exhibits the relation which the metals enumerated as- 
sume to each other, in the acid and saline solutions usually employed as ex- 
citing fluids. But the relation of any one metal to another is not the same in 
all exciting fluids. Thus when tin and copper are placed in acid solutions, 
the former is most rapidly corroded and becomes the positive metal, accord- 
ing to its position in the series, but if they are put into a solution of ammonia 
which acts most upon the copper, then the latter becomes the positive metal. 
Copper is positive to lead in strong nitric acid, which oxidizes the former 
most freely, whereas in dilute nitric acid, by which the lead is most rapidly 
dissolved, the lead is positive. 



LIQUID ELEMENTS OF THE VOLTAIC CIRCLE. 

With the view of simplifying the statement of the chemical changes which 
occur in the voltaic circle, the exciting fluid has hitherto always been sup- 
posed to be hydrochloric acid (chloride of hydrogen,) and this compound is a 
fair type of the class of bodies which are available for the purpose of bringing 
these changes into play. The exciting fluid is always a saline body in the 
general sense, that is, a compound of salt-radical, such as chlorine, with a 
basyle, such as hydrogen or a metal. The chloride of copper, chloride of 
sodium, chloride of ammonium, or the chloride of any other basyle may be 
substituted for hydrochloric acid, although not all with the same advantage; 
and the chlorides of basyles may be replaced by their iodides, sulphatoxides 
(sulphates,) nitratoxides (nitrates) and salts of other acids, as exciting fluids, 
provided they have the condition of liquidity, which gives mobility to their 
particles and permits that disposition of them which is assumed in a polar 
chain. The liquids, which yield in the cell of decomposition, are of the same 
nature, although the liquid which forms the best exciting fluid is not always 
the most easily decomposed in the decomposing cell. 



172 INDUCTIVE AFFINITY. 

The positive metal which is exposed to the exciting fluid always acts in one 
way, displacing the basyle and combining with the salt-radical of that body; in 
the manner the zinc has been seen to liberate hydrogen and combine with chlo- 
rine, when hydrochloric acid is the exciting fluid. The positive metal is thus 
substituted for a similar basyle in a pre-existing saline compound. That metal 
may dissolve in another manner, by uniting directly, for instance, with free chlo- 
rine or iodine in solution, but then no polarization follows. A chain of particles 
of chlorine may extend from the zinc to the associated negative metal, but they 
are not polarized, as a chain of hydrochloric acid particles would be in the same 
circumstances. The particles of these free elements appear to be incapable of 
that polar condition, having chlorous affinity on one side and zincous on the 
other, of which both the solid and liquid constituents of the voltaic circle must 
be susceptible. Judging from the uniformity in composition of exciting liquids, 
their susceptibility of polarization depends on their consisting of an atom of basyle 
and an atom of salt-radical, which may become respectively the locus of zincous and 
chlorous polarity. Or as chlorine belongs to the salt-radicals and zinc to the ba- 
syles, and each may be taken to represent its class, the exciting bodies may be 
said to be capable of having a chlorous and zincous pole, because they consist 
of a chlorous and zincous element. Such particles may be looked upon as in 
a state of tension when forming a part of a polar chain, each about to divide into 
its chlorous and zincous atoms. Mr. Faraday has established that all exciting 
liquids are binary compounds of single equivalents of salt-radical and basyle, or 
proto-compounds, such as hydrochloric acid itself, proto-chloride of tin, &c. 
Other saline bodies which are per-compounds, such as bichloride of tin, are not 
exciting or polarizable, because, as it may be supposed, they are not naturally 
resolvable into a chlorous and zincous atom but into a chlorous atom and ano- 
ther salt ; the bichloride of tin, for instance, into chlorine and proto-chloride of 
tin. For such saline bodies may all be ternary compounds and consist of a 
binary compound united with an additional quantity of salt-radical. Certain 
proto-compounds, also, which are deficient in the saline character, are not 
polarizable, such as chloride of sulphur, protochloride of phosphorus and proto- 
chloride of carbon. These bodies do not contain a proper basyle. 

The zinc or positive metal, too, always forms a proto-compound in dissolving, 
which is a saline body. The order of the chemical changes in the exciting fluid 
therefore is as follows : the zinc in decomposing a binary compound and forming 
a binary compound, liberates an atom of its own class ; which atom repeats the 
same actions ; supplying at the same time another atom of the same kind to 
act in the same manner, and that another, from the zinc to the copper plate. 
The combining bodies are always a basyle and a salt-radical, and therefore only 
two kinds of attraction or affinity are at work throughout the chain, those of a 
basyle and a salt-radical, the zincous and chlorous affinities. Hence, in the 
present subject of chemical polarity, we have to deal with but two attractive 
forces, the zincous and the chlorous, as in magnetism with but two magnetic 
forces, the austral and the boreal. 

On the electrical hypothesis a body which is thus decomposed in the active 
cells, or in the cell of decomposition, is called an electrolyte (decomposable by 
electricity,) and this kind of decomposition is distinguished as electrolysis. The 
chemical expressions equivalent to these are zincolyte and zincolysis, the de- 
compositions throughout the circle being referred to the inductive action of the 
affinities of zinc or the positive metal. 

The characters of the two constituents of a zincolyte may be shortly noticed. 
The class of basyle constituents is composed of the metals in their order as 
positive metals, beginning with potassium and terminating with mercury, plati- 
num and the less oxidable metals. Ammonium has a claim to be introduced 
high in this list, and should probably be accompanied by the analogous basyles 



LIQUID ELEMENTS OF THE VOLTAIC CIRCLE. 173 

of the vegeto-alkalies, although in respect to the decomposition of their salts in 
the voltaic circle, we have no precise information. Hydrogen likewise finds a 
place near copper in this class. 

At the head of the salt-radical constituents of zincolytes may be placed iodine 
and the other members of the chlorine family. These are followed by the salt- 
radicals of the sulphates, nitrates, carbonates, acetates, and other oxygen-acid 
salts. Sulphur must be allowed to follow the last as the salt-radical of the solu- 
ble sulphurets,and the lowest place be assigned to oxygen, as the salt-radical of the 
soluble metallic oxides, of oxide of potassium, for instance, and of water. It is un- 
usual to speak of oxygen as a salt-radical, and of caustic potash and water as salts, 
but the binary theory of salts recognises no essential difference between the chlo- 
ride, sulphatoxide, and oxide of a basyle, the oxide being connected with the 
more highly saline compounds through the sulphuret, and the chain of salt-radi- 
cals from iodine to oxygen being continuous and unbroken. 

The facility of decomposition of different zincolytes appears to depend 
more upon the high place of their salt-radical than upon the nature of their other 
constituent. The iodides, for instance, as iodide of potassium and hydriodic 
acid, are the most easily decomposed of all salts, yielding to the polar influ- 
ence of the single circle. Then follow the chlorides, — chloride of lead, fused 
by heat, yielding to a very moderate power. After these the salts of strong 
oxygen acids, such as sulphates and nitrates either of strong bases, such as 
potash and soda, or of weak bases, such as oxide of copper and water (the 
hydrated acids are such salts.) The carbonates and acetates, which have 
much weaker salt-radicals, are still less easily decomposed, and finally oxides 
are decomposed with great difficulty. Water itself is polarized with such 
extreme difficulty, and decomposed when alone to so minute a degree, even 
by a powerful battery, as to leave its claim to be considered a zincolyte when 
in a state of purity by no means certain. 

Widely as the more characteristic salt-radicals and basyles differ, still the 
classes pass by imperceptible gradations into each other, and form portions of 
one great circle. Mercury and the more negative metals, although clearly 
basyles, appear at times to assume the salt-radical relation to the highly posi- 
tive metals; such a character is evinced in mercury, by the energy with which 
it unites with sodium and potassium, and by its function in the amalgamated 
zinc plate of the voltaic circle. So that the salt-radical or basyle character of 
a body is not absolute, but always relative to certain other bodies. 

The addition of a salt or acid, even in minute quantity, to water in the cell 
of decomposition, causes the copious evolution of oxygen and hydrogen gases 
at the zincoid and chloroid, and is therefore often spoken of as facilitating, by 
its presence, the decomposition of the water, in some way which cannot be 
explained. But the phenomena are unattended with difficulty on the binary 
theory of saline bodies. When sulphate of soda exists in the water of the de- 
composing cell, it is sulphatoxide of sodium which is decomposed, S0 4 , the 
sulphate radical being evolved at the zincoid and sodium at the chloroid. But 
the sodium having a strong affinity for oxygen reacts upon the water at the 
pole, forming soda and liberating hydrogen, which therefore appear together; 
while S0 4 having, as a high salt-radical, a powerful affinity for hydrogen, 
likewise decomposes water, and thus evolves oxygen, which, with a free acid, 
appears at the zincoid. A solution of chloride of sodium is decomposed in 
the same manner, its elements chlorine and sodium being attracted to the zin- 
coid and chloroid respectively, but neither of these elements appearing as such. 
Both decompose water and thus produce oxygen with hydrochloric acid at 
the zincoid, and soda with hydrogen at the chloroid. It has indeed been as- 
certained that the polar influence which apparently effects two decompositions 
in these circumstances, namely, that of water into oxygen and hydrogen, and 

15* 



174 INDUCTIVE AFFINITY. 

of a salt into its acid and alkali, is no more in quantity than is necessary to 
decompose one of these bodies, the circulating power being measured by the 
quantity of fused chloride of lead decomposed in another part of the circuit 
(Daniell.) There can be little doubt then that only one binary compound 
is immediately decomposed, and that the two sets of products which appear 
at the poles, are the results of secondary decomposition. Indeed the decom- 
position of salts in the voltaic circle affords considerable support to the binary 
theory of these bodies (page 134.) 

Secondary decompositions: — The products of voltaic action are frequently 
of that secondary character, the original products being lost from their reaction 
upon the liquid in which they are produced, or upon the substance of the me- 
tallic poles. Thus salts of the vegetable acids often afford carbonic acid, and 
salts of ammonia nitrogen, instead of oxygen, at the zincoid; the oxygen libe- 
rated having reacted upon the combustible constituents of these bodies. Ni- 
trates, again, may afford nitrogen, or nitric oxide, at the chloroid, in conse- 
quence of the oxidation of the hydrogen evolved there. The nascent condi- 
tion of the liberated elements favours such secondary actions. When the 
zincoid is composed of a positive metal, such as zinc itself or copper, the 
chlorous element is absorbed there, combining with the metal. The decom- 
position of a salt is also then much easier, the action of the circle being. greatly 
assisted by the proper affinity of the matter of the zincoid for a chlorous body. 
Insoluble sulphurets, chlorides and other compounds of a positive metal act- 
ing as the zincoid, have thus been slowly produced, in a single circle with a 
weak exciting fluid ; w T hich products have exhibited distinct crystalline forms, 
resembling natural minerals, not otherwise producible by art. The hydrogen 
evolved upon a platinum chloroid, immersed in the solution of a copper or iron 
salt, may also reduce these metals upon the surface of the platinum, in the form 
of brilliant octahedral crystals. In the active cells themselves a secondary de- 
composition is apt to occur, the hydrogen evolved decomposing the salt ,of zinc 
which accumulates in the liquid, and occasioning a deposition of that metal upon 
the copper plate ; an occurrence which may determine an opposite polarity, and 
cause the action of the circle to decline. But on disconnecting the zinc and 
copper plates, the foreign deposite upon the latter is quickly dissolved off by 
the acid. The inconvenience of this secondary decomposition in the exciting 
cells is avoided by dividing the cell into two compartments, by a porous plate 
of earthenware, or by a humid membrane, interposed between the zinc and 
copper plates. The salt of zinc formed about that metal is prevented from dif- 
fusing to the copper, by the diaphragm, although it allows, from its porosity, a 
continuity of liquid polarizable particles between the metals. 

Before leaving the subject of the liquid and solid elements of the voltaic 
circle, I may offer for consideration some opinions respecting their internal 
constitution, of a more speculative character, which the chemical theory of the 
voltaic circle suggests. 

The phenomena of electricity of friction, and high of tension appear to in- 
dicate that all compound bodies whatever are polarizable, under an intense in- 
duction. On the chemical theory this would imply that they are all binary 
compounds, or at least capable of a binary disposition of their elements. And 
it is remarkable that recent discovery has detected such a constitution in several 
bodies containing a large number of atoms, and has rendered it probable in a 
great many others; ether, for instance, has been found to be the oxide of ethyl, 
benzoic acid the oxide of benzoyl, and all the essential oils appear to be bodies 
of a similar constitution. But the molecular constitution of such complex 
compounds appears not to be fixed and invariable. Alcohol for instance, when 
free may be the hydrate of ether, that is a ternary compound; but alcohol replaces 
water in some salts, and then appears as a binary compound, or the oxide of 



LIQUID ELEMENTS OF THE VOLTAIC CIRCLE. 175 

a new basyle, which is ethyl plus an atom of water. It is not improbable then 
that under the influence of a powerful induction, compounds may admit of 
different dispositions of their molecules; that the strong chlorous affinity of a 
contiguous polar molecule may develope near it a zincous element, in the 
most complicated substance. 

It comes to be a most interesting subject of inquiry, which I trust is not 
beyond our reach, what relation have the atoms of a metallic element of the 
circle to each other, when not in a polar condition? The relation I imagine 
to be that of combination. Their atoms assume so readily the binary or saline 
arrangement under induction, that they may be supposed already to possess 
it. Their atoms may be associated in a congeries, forming a highly complex 
molecule, the prototype of a saline body, in which not only the salt-radical and 
basyle have their representative atoms of metal, but even the elements of con- 
stitutional water, and of water of crystallization. Numerous and most in- 
teresting inquiries are suggested by the possible existence of such a molecular 
structure of the metal. As salts differ from each other in the number and dis- 
position of these accompanying bodies, a sulphate of zinc in its water of crys- 
tallization, for instance, from a chloride of the same metal, so one metal may 
differ from another in the arrangement which it affects, or salt it resembles. 
The molecular arrangement in a metal may even change with its temperature; 
such arrangements, and the changes they undergo, occasioning a variable in- 
ductive action of dissimilar metals in contact upon each other's molecules, and 
giving rise, in particular, to the phenomena of thermo-electricity. 

But the facility with which the polar condition of the molecules of a metal 
may be reversed, with a change in the direction in the induction affecting it, 
forbids us to suppose that any particular molecular arrangement of a metal is 
constant. The metal zinc may have one arrangement which it affects when 
under no foreign influence, (an arrangement, it may be, impressed upon that 
metal in its reduction from the ore, by the chemical agencies then at work,) 
but under the influence of different exciting fluids, it must assume different 
arrangements, analogous to those of the exciting fluid, at one time representing 
a chloride of zinc, and at another time a sulphate, or reflecting the molecular 
constitution of the exciting fluid, whatever that may be. To avoid complica- 
tion, attention has hitherto been confined to the action of the primary affinity 
of the exciting acid (that of its salt-radical) upon the zinc, but the secondary af- 
finities of the accessory constituents of the exciting acid must also be supposed 
to act upon the positive metal, although in a subsidiary manner to the primary 
affinity. 

In the constitution of many compound bodies, a provision for the formation 
of new compounds is observed, similar to what is now supposed to exist in 
the zinc. In the crystallized sulphate of zinc itself, there is a provision, in the 
single constitutional atom of water of that salt, for the formation, by replace- 
ment, of the double sulphate of zinc and potash, and in the water of crystalli- 
zation of the same salt, provision for the formation of various subsalts con- 
taining excess of oxide of zinc or ammonia, by similar replacements. The 
assumed molecular structure of the metal, thus leads to a farther development 
of the extending law of substitution. 

The peculiarities of iron, by which it is enabled to resist amalgamation, to 
assume magnetism, to exhibit an indifference to nitric acid in certain circum- 
stances, must depend upon the molecular structure of that metal, and are sub- 
jects which the chemist approaches with advantage when unfettered by the 
electrical hypothesis. 



176 INDUCTIVE AFFINITY. 



GENERAL SUMMARY". 



1. No chemical affinity has been observed to act inductively, but that kind 
which has been described as operating in the voltaic circle. The affinity be- 
tween two salts, the affinity of one metal for another, of one metal for a free 
non-metallic element, &c, appear to be incapable of acting in this way; or it 
may be that we have not the means of observing the inductive mode of action 
of these affinities. The action of the circles which have been formed of or- 
ganic matters, such as slices of brain and beet-root, or the combinations of 
acid, alkali, and salts, employed by Becquerel, are too minute and obscure, to 
interfere with this general conclusion. That arrangement also of pairs of thin 
discs of positive and negative metals, with paper between each pair, which is 
known as the dry pile, acts only, it is admitted, when damp, and therefore 
when oxidation of the positive metal may occur. 

2. The exciting compound or zincolyte must have a polar molecule, which 
requires it to consist of single zincous and chlorous atoms. 

3. The molecules of the zincolyte must also have mobility and be able to 
assume a polar arrangement, or place themselves with their unlike and attrac- 
tive poles together, so as to form a polar chain. This necessitates fluidity of 
the zincolyte (Faraday.) 

4. Of the metallic portions of the circle, the molecule is indifferently pola- 
rizable, that is, either side of it indifferently may become chloro-polar or zinco- 
polar, according to the direction of the induction affecting it. Hence these 
portions of the circle need not be fluid like the zincolytes. 

5. In a closed voltaic circle, a certain number of lines or chains of polarized 
molecules is established, each chain being continuous round the circle. 
Hence the polar condition of the circle must be every where the same. The 
same number of particles of exciting fluid are simultaneously polar upon the 
surface of every zinc plate in the active cells, and also upon the surface of 
the zincoid in the cell of decomposition, and the consequent chemical change, 
or decomposition occurring, is of the same amount in the same time in all 
the cells. Such equality in condition and results is essential to a rotal induc- 
tion, such as exists in the voltaic circle. 

The number of polar chains that can be established at the same time in a 
particular voltaic arrangement, is obviously affected by several circumstances: 

(1) By the size of the zinc plate; the number of particles of zinc that may 
be simultaneously acted upon by the exciting fluid, being directly propor- 
tional to the extent of metallic surface exposed. 

(2) By the nature and accidental state of the exciting liquid, some zinco- 
lytes being more easily acted on by the positive metal than others; while the 
state of dilution, temperature, and other circumstances may affect the facility 
of decomposition of any particular zincolyte. 

(3) The adhesion of the gas bubbles of hydrogen to the copper plate, at 
which they are evolved, interferes much with the action of a battery. By 
taking up the hydrogen, by means of a solution of sulphate of copper in con- 
tact with the copper plate, Mr. Daniell increased the amount of circulating 
force six times. 

(4) The chemical action in a cell is also diminished by increasing the dis- 
tance from each other in the exciting fluid of the positive and negative metals. 

(5) The lines of chemico-polar molecules in the exciting fluid should be re- 
pulsive of each other, like lines of magneto-polar elements, as illustrated in the 
mutual repulsion and divergence of the threads of steel filings which attach 
themselves to the pole of a magnet (Fig. 48.) That the lines of induction do 
diverge greatly in the acid, starting from the zinc as a centre, is placed beyond 



GENERAL SUMMARY. 177 

doubt by many experiments of Mr. Daniell. A small ball of zinc suspended in 
a hollow copper globe filled with acid, is the arrangement in which this diver- 
gence is least restrained, and was found to be the most effective form of the vol- 
taic circle. When the copper too, is a flat plate, and wholly immersed in the 
acid, the back is found to act as a negative surface, as well as the face directly 
exposed to the zinc, showing that the lines of induction in the acid expand and 
open out from each other, some bending round the edge of the copper plate and 
terminating their action, after a second flexure, on its opposite side. To col- 
lect these diverging lines, the surface of the copper may be increased with ad- 
vantage to at least four times that of the zinc. 

(6) The polar chains of molecules, in the connecting wires and other metal- 
lic portions of the circle, must be equally repulsive of each other. Hence the 
small size of the negative plates in the active cells, and of the platinum plates in 
the cell of decomposition, and the thinness of the connecting wires, are among 
the circumstances which diminish the number of polar lines that can be esta- 
blished, and impair the general efficiency of a battery. 

6. The effect of multiplying the active cells in a battery is not to increase the 
number of polar chains, or quantify of induced particles, but to increase the in- 
tensity of the induction in each chain ; although this increase in intensity 
generally augments the quantity also, in an indirect manner, by overcoming 
more or less completely such obstacles to induction as have been enumerated. 

7. The intensity of the induction, also, is much greater with some zincolytes 
than others. Thus a single pair of zinc and platinum plates excited by dilute 
sulphuric acid, decompose iodide of potassium, proto-chloride of tin and fused 
chloride of silver, but not fused nitre, chloride or iodide of lead or solution of 
sulphate of soda. With the addition, however, of a little nitric acid to the sul- 
phuric, the same single circle decomposes all these bodies, and even water 
itself. The evolution of hydrogen gas on the negative metal is at the same 
time suppressed by the nitric acid, which exerts a secondary action on that 
element. 

8. The division of the connecting wire, and the separation of its extremities 
to the most minute distance from each other, is sufficient to stop all induction 
and the propagation of the polar condition. In the most powerful voltaic 
battery ever arranged, that which Mr. Daniell lately operated with, consisting 
of seventy of his large cells, no induction was observed to pass when the 
terminal wires were separated, not more than the one-thousandth of an inch 
even with the flame of a spirit-lamp or rarified air between them. Absolute 
contact of the wires was necessary to establish the circulation. But after 
contact was made, and the wires were heated to whiteness, they might be se- 
parated to a small distance without the induction being interrupted; the space 
between them was then filled with an arch of dazzling light, containing de- 
tached particles of the wire in a state of intense ignition, which were found to 
proceed from the zincoid to the chloroid, the former losing matter, and the 
other acquiring it. So highly fixed a substance as platinum is carried from 
pole to pole in this manner; but the transference of matter is most remarkable 
between charcoal poles, which may be separated to the greatest distance, and 
afToid the largest and most brilliant arch of flame. A similar, although it may 
be an excessively minute detachment of matter, is found to accompany the 
electric spark in ail circumstances. Hence, the electric spark always con- 
tains matter. 

9. When terminal wires of a voltaic circle are grasped in the hands, the circuit 
may be completed by the fluids of the body, provided the battery contains a 
considerable number of cells and the induction is of high intensity; the nervous 
system is then affected, the sensation of the electric shock being experienced. 

10. The conducting wire becomes heated precisely in proportion to the 



178 



INDUCTIVE AFFINITY. 



number of polar chains established in it, and consequently in proportion to the 
size of the zinc plate; and this to the same degree from the induction of a sin- 
gle cell, as from any number of similar cells. Wires of different metals are 
unequally heated, according to the resistance which they offer to induction. 
The following numbers express the heat evolved by the same circulation in 
different metals, as observed by Mr. Snow Harris. 



Heat evolved. 


Resistance. 


Silver 


6 . . 


. 1 


Copper 


6 . 


. 1 


Gold 


9 


. . H 


Zinc . . 


18 . 


. 3 


Platinum 


.30 . 


. 5 


Iron 


.30 . 


. 5 


Tin . ' . 


.36 . . . . 


. 6 


Lead 


.72 . 


. 12 


Brass 


.10 . 


. 3 



The conducting powers of the metals are inversely as these numbers; silver 
being a better conductor than platinum in the proportion of 5 to 1. The con- 
ducting power of all of them is found to be diminished by heat. 

11. As a portion of the voltaic circle, the conducting wire acquires extraordi- 
nary powers of another kind, which can only be very shortly stated here, 
belonging as they properly do to physics. 

(1) Another wire placed near, and parallel to the conducting wire has the 
polar condition of its molecules disturbed, and an induction propagated through 
it in an opposite direction to that in the conducting wire. 

• (2) If the conducting wire be twisted in the manner of a cork-screw so as 
to form a hollow spiral or helix, it will be found in that form to represent a 
magnet, one end of the helix being a north, and the other a south pole; and, if 
moveable, will arrange itself in the magnetic meridian, under the influence of 
the earth's magnetism. Its poles are attracted by the unlike poles of an ordi- 
nary magnet, and it imparts magnetism to soft iron or steel by induction. 
Two such helices attract and repel each other by their different poles, like two 
magnets. Indeed an ordinary magnet may be viewed as a body having a he- 
lical chain of its molecules in a state of permanent chemico-polarity. 

(3) If a bar of soft iron bent into the form of a horse shoe, with a copper 
wire twisted spirally round it, be applied like a lifter to the poles of a perma- 
nent magnet, in the instant of the iron becoming a magnet by induction, the 
molecules of the spiral wire become chemico-polar, and when contact is broken 
with the permanent magnet, and the soft iron ceases to be a magnet, the wire 
exhibits a polarity the reverse of the former. By a proper arrangement, 
electric sparks and shocks may be obtained from the wire, while the soft iron 
included within it is being made and unmade a magnet. The magneto-electric 
machine, is a contrivance for this purpose, and is now coming to supersede 
the old electric machine, as a source of what is termed electricity of tension. 
Magnetic and electric effects are thus reciprocally produced from each other. 

(4) When the pole of a magnetic needle is placed near the conducting wire, 
the former neither approaches nor recedes from the latter, but exhibits a dis- 
position to revolve round it. The extraordinary and beautiful phenomena of 
electrical rotation are exhibited in an endless variety of contrivances and ex- 
periments. As the magnetic needle is generally supported upon a pivot, it is 
free to move only in a horizontal plane, and consequently when the conduct- 
ing wire is held over or under it (the needle being supposed in the magnetic 
meridian,) the poles in beginning to describe circles in opposite directions round 
the wire, proceed to move to the right and left of it, and thus deviate from the 




General summary. 179 

true meridian. The amount of deviation in degrees is proportional to the 
quantity of circulating induction; and may be taken to represent it, as is done 
in a useful instrument, the galvanometer, to be afterwards described. It was 
in the form of these deflections, that the phenomena exhibited by a magnet, 
under the influence of a conducting wire, first presented themselves to Oersted 
in 1819. 

12. Thermo-electrical phenomena are produced from the effect of unequal 
temperature upon metals in contact. If heat be applied p IG< gi # 
to the point c, (Fig. 61.) at which two bars of bismuth and 
antimony b and a are soldered together, on connecting the 
free extremities by a wire, the whole is found to form a 
weak voltaic circle, with the induction from b through the 
wire to a. Hence in this thermo-polar arrangement the bis- 
muth is the negative metal, and may be compared to the 
copper in the voltaic cell. If cold instead of heat be applied II 
to c, a current also is established, but in an opposite direction 
to the former. Similar circuits may be formed of other me- 
tals, which may be arranged in the following order, the most 
powerful combination being formed of those metals which are most distant 
from each other in the following enumeration: bismuth, platinum, lead, tin, 
copper or silver, zinc, iron, antimony. When heated together, the current 
proceeds through the wire from those which stand first to the last According 
to Nobili, similar circuits may be formed with substances of which the con- 
ducting power is lower than that of the metals. 

Several pairs of bismuth and antimony bars may be associated as in Fig. 62, 
and the extreme bars being connected by a Fig, 62. 

wire, form an arrangement resembling a com- 
pound voltaic circle. Upon heating the upper 
junctions, and keeping the lower ones cool, or 
on heating the lower ones and keeping the 
others cool, an induction is established in the 
wire more intense than in the single pair of 
metals, but still very weak. The conducting 
wire strongly affects a needle, causing a deflec- 
tion proportional to the inequality of tempera- 
ture between the ends of the bars. Melloni's thermo-multiplier is a delicate in- 
strument of this kind, which is even more sensitive to changes of temperature 
than the air thermometer, and has afforded great assistance in exploring the phe- 
nomena of radiant heat (page 46.) 

In such a compound bar, also unequal temperature may be produced, by 
making it the connecting wire of a single and weak voltaic circle ; whereupon the 
metals become cold at their junction, if the induction is from the bismuth to the 
antimony, and hot at the same point if the induction is in the opposite direction. 
These are the converse of the preceding phenomena, in which electrical effects 
were produced by inequality of temperature. 

13. The friction of different bodies is another source of electrical phenomena. 
One, at least, of the bodies rubbed together must not be a conductor, and in 
general, two non-conductors are used. When a silk handkerchief or a piece of 
resin is rubbed upon glass, both are found, after separation, in a polar condition, 
and continue in it. The rubbing surface of the glass is zinco-polar, and that of 
the resin or silk is chloro-polar, and a molecular polarization is at the same time 
established through the whole mass of both the glass and resin, reaching to their 
opposite surfaces, which exhibit the other polarity. The powers thus appearing 
on the two rubbing surfaces, being manifestly different, were distinguished by 
the names of the bodies on which they are developed, that upon the glass as 




180 INDUCTIVE AFFINITY. 

vitreous electricity (zincous affinity,) and that upon the resin as resinous elec- 
tricity (chlorous affinity.) 

In comparing the chemico-polarity excited by friction with that of the voltaic 
circle, we observe that the former is of high intensity but small in quantity, or 
affecting only a small number of trains of molecules. If both the excited vitre- 
ous and resinous surfaces have a conducting metal, such as a sheet of tin-foil 
applied to them, and each sheet have a wire proceeding from it, the wires and 
tin-foil are polarized similarly to the glass and the resin which they cover, and 
a zincolyte placed between the extremities of the wires, which are respectively 
a zincoid and chloroid, is polarized also and decomposed. But the amount of 
decomposition, which is a true quantity of induced particles, is extremely mi- 
nute compared with the amount of induction in the voltaic circle. Thus Mr. 
Faraday, has calculated that the decomposition of one grain of water by zinc 
in the active cell of the voltaic circle, produces as great an amount of polari- 
zation and decomposition in the cell of decomposition, as 950,000 charges of a 
large Leyden battery, an enormous quantity of power, equal to a most destruc- 
tive thunder storm. The polarization from friction is therefore singularly intense, 
although remarkably deficient in quantity, or in the number of molecules af- 
fected. 

The kinds of matter susceptible of this intense polarization are so many, and 
so various, such as glass, minerals, wood, resins, sulphur, oils, air, &c, as to 
make it difficult to suppose that the polar molecule is of the same chemical con- 
stitution in all of them, as it is in the zincoly tes of the voltaic circle. Indeed it 
must be admitted that all matter whatever may be forced into a polar condition, 
by a most intense induction. Under such influence, too, the molecule appears 
to be indifferently polar. 

Electrical induction at a distance, Mr. Faraday has shown to be always an 
action of contiguous particles, chains of particles of air, or some other " die- 
lectric," extending between the excited body which is inducing, and the in- 
duced body. His investigation of this subject led to the remarkable discovery 
that the intensity of electric induction at a constant distance from the inducing 
body, is not always the same, but varies in different media, the induction 
through a certain thickness of shell-lac, for instance, being twice as great as 
through the same thickness of air. Numbers may be attached to different bo- 
dies which express their relative inductive capacities: — 

Specific inductive capacity of air ... 1 

„ glass . . . 1.76 

,, „ shell-lac . . .2 

,, „ sulphur . . . 2.24 

The inductive capacity of all gases is the same as that of air, and this property, 
it is remarkable, does not alter in these bodies with variations in their density. 



VOLTAIC INSTRUMENTS. 

Voltaic battery. — The working forms of the battery are too numerous to be 
individually noticed. That form only need be particularly described which is 
the most nearly perfect, and which in experiments of research is likely to su- 
persede all others, — the constant battery of Mr. Daniell. A cell of this bat- 
tery consists of a cylinder of copper 3£ inches in diameter, which experience 
has proved to the inventor to afford the advantageous distance between the 
metallic surfaces, but which may vary in height from 6 to 20 inches, according 
to the power which it is wished to obtain. A membranous bag formed of the 
gullet of an ox, is hung in the centre by a collar and circular copper plate, 



VOLTAIC INSTRUMENTS. 



181 



Fig. 63. 




(Daniell's Introduc- 



Fig. 64. 



resting upon a rim within and near the top of the cylinder; and in this is sus- 
pended by a wooden cross bar, a cylindrical rod of amalgamated zinc half an 
inch in diameter. The outer cell is charged with a mixture of 8 measures of 
water and one of oil of vitriol, which has been saturated with sulphate of cop- 
per, and portions of the solid salt are placed upon the 
circular copper plate, which is perforated like a 
colander, for the purpose of keeping the solution 
always in a state of saturation. The internal tube is 
filled with the same acid mixture without the salt of 
copper. A tube of porous earthenware, shut at the 
bottom, may be substituted for the membrane with 
great convenience, but Mr. Daniell believes with 
some little loss of power. A section of the upper 
part of one of these cells is here represented, abed 
is (Fig. 63) the external copper cylinder; efgh, the 
internal cylinder of earthenware, and / m the rod of 
amalgamated zinc. Upon a ledge c d, within an 
inch or two of the top of the cylinder, rests the cy- 
lindrical colander i k, which contains the copper salt, 
and both the sides and bottom of which are perfo- 
rated with holes. A number of such cells may be 
connected into a compound circuit, with wires 
soldered to the copper cylinders, and fastened to the 
zinc by clamps and screws as shown below. Fig. 64. 
tion to Chemical Philosophy, page 440.) 

In this instrument the sulphate of zinc, formed by the solution of the zinc 
rod, is retained in the mem- 
branous bag or stoneware 
cylinder, and prevented 
from diffusing to the cop- 
per surface; while the hy- 
drogen, instead of being 
evolved as gas on the sur- 
face of the latter metal, de- 
composes the oxide of cop- 
per of the salt there, and 
occasions a deposition of 
metallic copper on the cop- 
per plate. Such a circle 
will not vary in its action 
for hours together, which 
makes it invaluable in the 
investigation of voltaic 

laws. It owes its superiority principally to three circumstances: — to the 
amalgamation of the zinc, which prevents the waste of that metal by solution 
when the circuit is not completed; to the non-occurrence of the precipitation 
of zinc upon the copper surface; and to the complete absorption of the hydro- 
gen at the copper surface, the adhesion of globules of gas to the metallic 
plates greatly diminishing, and introducing much irregularity into the action of 
a circle. 

Bird's battery and decomposing eel/.— To M. Becquerel we are particularly 
indebted for the investigation of the decomposing powers of feeble currents, sus- 
tained for a long time, the results of which are of extreme interest, both from 
the nature of the substances that can be thus decomposed, and from the form 
in which the elements of the body decomposed are presented, the slow formation 
16 




11 • III 



182 



INDUCTIVE AFFINITY. 




of these bodies permitting their deposition in regular crystals .* Dr. Golding 
Bird has also added to the number of bodies decomposed by such means, and 
contrived a simple form of the battery, which with Becquerel's decomposing 
cell, renders such decompositions certain and easy, and forms indeed the voltaic 
instrument, perhaps above all others, the most directly useful to the chemist, f 
Fig. 65. Tne decomposing cell consists of a glass 

cylinder a, (Fig. 65,) within another 
glass cylinder b. The inner cylinder 
a is 4 inches long and li inch in 
diameter, and is closed at the lower end 
by a plug of plaster of Paris 0.7 inch in 
thickness: this cylinder is fixed by 
means of wedges of cork within the 
other, which is a plain jar, about 8 inches 
deep by 2 inches in diameter. A piece 
of sheet copper c, 4 inches long and 3 
inches wide, having a copper conduct- 
ing wire soldered to it, is loosely coiled 
up and placed in the inner cylinder 
with the plaster bottom : a piece of sheet zinc z, of equal size, is also loosely 
coiled, and placed in the outer cylinder ; this zinc likewise being furnished with 
a conducting wire. The outer cylinder is then nearly filled with a weak solu- 
tion of common salt, and the inner with a saturated solution of sulphate of cop- 
per. The two fluids are prevented from mixing by the plaster diaphragm, and 
care being taken that they are at the same level in both the cylinders, the cir- 
cle will afford, on joining the wires, a continuous current for weeks, the chlo- 
ride of sodium and the sulphate of copper being very slowly decomposed. After it 
has been in action for some weeks, chloride of zinc is found in the outer cylin- 
der : and beautiful crystals of metallic copper, frequently mixed with the ruby 
suboxide (closely resembling the native copper ruby ore,) with large crystals of 
sulphate of soda are found adhering to the copper plate in the smaller cylinder, 
especially on that part where it touches the plaster diaphragm. 

The decomposing cell is the counterpart of the battery itself, consisting like 
it of two glass cylinders, one within the other, the smaller one having a bottom 
of plaster of Paris fixed into it : this smaller tube may be about ^ inch wide and 
3 inches in length, and is intended to hold the metallic or other solution to be 
decomposed, the external tube d, in which the other is immersed being filled 
with a weak solution of common salt. In the latter solution a slip of amalga- 
mated zinc-plate z\ soldered to the wire coming from the copper plate c of the 
battery, is immersed ; and a slip of platinum foil pf, connected with the wire 
from the zinc plate 2 of the battery, is immersed in the liquor of the smaller tube, 
being held in its place by a cork, through which its wire passes. The whole 
arrangement is now obviously a pair of active cells, of which c z' is one metallic 
element, and z pi the other ; and the fluid between z and c divided by the po- 
rous plaster diaphragm, one fluid element, and the fluid between z and jo/, di- 
vided by a porous plaster diaphragm, another fluid element ; although it will be 
convenient to speak of the last as the cell of decomposition. With a solution of 
chlorides or nitrates of iron, copper, tin, zinc, bismuth, antimony, lead or silver, 
in the smaller tube, Dr. Bird finds the metals to be reduced upon the surface of 
the platinum, generally but not invariably in possession of a perfect metallic lus- 
tre, always more or less crystalline and often very beautifully so. The crys- 
tals of copper rival in hardness and malleability, the finest specimens of native 
copper, and those of silver, which are needles, are white and very brilliant. The 
solution of fluoride of silicon in alcohol being introduced into the small tube by 

* Traile Experimental de TElectricite et du Magnehsme, par. M. Becquerel. 
t Phil. Trans. 1837, p. 37. 



VOLTAIC INSTRUMENTS. 



183 



Dr. Bird, a deposition of silicon upon the platinum was found to take place in 
24 hours, which was nearly black and granular and is described as exhibiting 
a tendency to a crystalline form. From an aqueous solution of the same fluoride, 
a deposition of gelatinous silica was observed to take place around the reduced 
silicon, mixed with which, or precipitated in a zone on the sides of the tube, 
especially if of small diameter, frequently appear minute crystalline grains of 
silica or quartz, of sufficient hardness to scratch glass, and appearing translucent 
under the microscope. With a modification of the decomposing cell described, 
Dr. Bird succeeded in decomposing a solution of chloride of potassium, 
and obtained an amalgam of potassium. The inner tube e. was replaced 
by a small glass funnel, the lower opening of which was stopped with 
stucco, and which thus closed retained a weak solution of the alkaline 
chloride poured into it. Every thing external to this funnel remaining 
as usual, mercury contained in a short glass tube, like a thimble, was placed 
in the funnel, and covered by the liquid, and instead of the platinum plate, a 
platinum wire coiled into a spiral at the extremity, was plunged into the mer- 
cury, the other end of this wire being connected with the zinc plate z, 
of the battery. The circuit having been thus completed, the mercury had 
swollen in eight or ten hours to double its former bulk, and when afterwards 
thrown into distilled water, evolved hydrogen and produced an alkaline solu- 
tion. A solution of hydrochlorate of ammonia being substituted for that of 
chloride of potassium, in this experiment, the metal swells to 5 or 6 times 
its bulk in a few hours, and the semifluid amalgam of ammonium is formed. 
These feeble currents thus effect decompositions, in the lapse of time, which 
batteries of the ordinary form and considerable magnitude, may effect very 
imperfectly, or fail entirely in producing. 

Volta-meter. — The decomposing power of a battery is represented by the 
quantity of oxygen and hydrogen gases evolved in a cell of decomposition 
containing dilute sulphuric acid. The volta-meter 
is simply a cell so charged, and of a proper form 
to allow of the gases evolved being collected and 
measured. One of the simplest forms is that con- 
structed for me by Mr. Young. It is a stout 
eight ounce phial (Fig. 66,) through the cork of 
which two platinum wires are passed, with flat 
plates of platinum attached to them within the 
bottle, which become the terminal plates of the 
battery when its wires are thrust into the cavaties 
of two small hollow brass cylinders attached ex- 
ternally to the platinum wires of the apparatus. 
The gases escape by a bent glass tube flitted into 
the cork of the bottle, and may be collected in a 
graduated jar at a small pneumatic trough. In 
this instrument steel plates may be substituted 
for the platinum, provided a solution of carbonate 
of potash be used instead of dilute sulphuric 
acid. 

Galvanometer. — The sensibility of the magnetic needle to the influence of 
the conducting wire of a voltaic circle brought near it, has been applied to the 
construction of an instrument which will indicate the feeblest polarization or 
slightest current in the connecting wire. It consists of a pair of magnetic 
needles (Fig. 67,) fixed on one axis with their attracting poles opposite each 
other, so as to leave them little or no directive power and render them astatic, 
which is delicately suspended by a single fibre of unspun silk. The lower 
needle is enclosed within a circle formed by a hank of covered wire, of which 



Fig. 66. 




184 



INDUCTIVE AFFINITY. 



the extremites a and b terminate in little cups containing mercury. When the 
terminal wires of a battery are introduced into the same cups, the hank of 

wire of the galvanometer be- 
comes part of the connecting 
wire, and the needle is deflected. 
The inductions proceeding in one 
direction above the needle and 
returning in the opposite direc- 
tion below needle, conspire to 
produce the same deflection; and 
the upper needle having its poles 
reversed, is deflected in the same 
direction, by the wire below it, 
as the lower needle is by the 
wire above it. Every turn of 
the wire also, repeats the influ- 
ence upon the needle, so that the 
deflection is increased in propor- 
tion to the number of turns or 
coils in the hank of wire. 




PART II. 
CHAPTER I. 

N O N-M ETALLIC ELEMENTS. 
SECTION I. 

OXYGEN. 

Equivalent 100, or 8, on hydrogen scale; symbol 0; density 1102.6 (air = 
1000); combining measure Q [one volume.) 

The following thirteen of the fifty-five elementary bodies known are in- 
cluded in the class of non-metallic elements: — oxygen, hydrogen, nitrogen, 
carbon, boron, silicon, sulphur, selenium, phosphorus, chlorine, bromine, 
iodine, and fluorine. Of these, oxygen, from certain relations which it bears 
to all the others, and from its general importance, demands or first attention. 

The name oxygen is compounded of o|y$ acid, and yeiteul I generate, and 
was given to the element of which I am about to treat by Lavoisier, with re- 
ference to its property of forming acids in uniting with other elementary bo- 
dies. Oxygen is a permanent gas, when uncombined, and forms one fifth part 
of the air of the atmosphere. In a state of combination, this element is the 
most extensively diffused body in nature; entering as a constituent into water, 
into nearly all the earths and rocks of which the crust of the globe is composed, 
and into all organic products with a very few exceptions. It was first recog- 
nised as a distinct substance by Dr. Priestley in this country, in 1774, and 
about a year afterwards by Scheele in Sweden, without any knowledge of 
Priestley's experiments. From this discovery may be dated the origin of trite 
chemical theory. 

Preparation. — Oxygen gas is generally disengaged from some compound 
containing it, by the action of heat. 

1°. It was first procured by Priestley, by heating red precipitate (peroxide 
of mercury,) which is thereby resolved into fluid mercury and oxygen gas. 
To illustrate the formation of oxygen in this way, 218 grains of red precipi- 
tate may be introduced into the body of a small retort a of hard or difficultly 
fusible glass; and the retort united in an air-tight manner with a small globular 
flask 6, having two openings, both closed by perforated corks, one of which 
admits the beak of the retort, and the other an exit tube c, of glass, bent as in 
the figure. The extremity of the exit tube is introduced into a graduated jar 

16* 



186 



OXYGEN. 



d, capable of holding 50 or 60 cubic inches, and placed in an inverted posi- 
tion, full of water upon the shelf of a pneumatic water-trough. Heat is then 
applied to the retort, by means of an Argand spirit lamp, powerful enough to 
raise it to a red heat, and maintain it at that temperature for a considerable time. 

Fig. 68. 




The first effect of the heat is to expand the air in the retort, bubbles of which 
issue from the tube c, and rise to the top of the jar d, displacing water; but 
more gas follows, which is oxygen, and at the same time metallic mercury 
condenses in the neck of the retort and runs down into the intermediate flask 
b. When the red precipitate in the retort has entirely disappeared, the lamp 
may be extinguished, and the retort allowed to cool completely. The end of the 
exit tube c being now above the level of the water in the jar, which is nearly 
full of gas, a portion of the latter, equal in bulk to the air which first left the 
retort, will return to it, from the contraction of the gas within the retort. The 
jar will be found in the end to contain 48 cubic inches of gas, which is there- 
fore the measure of oxygen produced in the experiment, and the flask to con- 
tain 202 grains of mercury. Now 48 cubic inches of oxygen weigh 16 grains; 
and a true analysis of the red precipitate has been effected, of which the result 
is, that 218 grains of that substance consists of — 

202 grains mercury. 
16 „ oxygen, (48 cubic inches.) 



218 



But oxygen gas is more generally derived from two other substances, oxide 
of manganese and chlorate of potash. 

2°. When the gas is required in large quantity, and exact purity is imma- 
terial, the oxide of manganese is preferred from its cheapness. This is a 
black, heavy mineral found in Devonshire and other parts of England, and of 
which upwards of 40,000 tons are consumed annually in the manufactures of 
the country. It is called an oxide of manganese, because it is a compound of 
the metal manganese with oxygen. In explanation of what takes place when 
this. substance is heated, it is necessary to state that manganese is capable of 
uniting with oxygen in several proportions, namely one equivalent, or 346 parts 
of manganese, with 100, and with 200 parts of oxygen, and two equivalents of 
manganese with 300 oxygen. These compounds are: — 



Protoxide of manganese 

Deutoxide 

Peroxide, or native black oxide 



Mn + O. 

2Mn + 30. 

Mn-f20. 



Now the peroxide however strongly heated, never loses more than one third 
of its oxygen, being converted into a compound of the first two oxides, that 



OXYGEN. 



187 



is, three equivalents of peroxide (1638 parts) lose two equivalents of oxygen 
(200 parts,) and leave a compound of one of deutoxide and one of protoxide; 
a change which may be thus expressed: — 

SMnO,- {l? a2 3+Ua0 . 

One of the malleable iron bottles in which mercury is imported, is readily 
converted into a retort, in which the black oxide may be heated, by removing 
its screwed iron stopper, and replacing this by an iron pipe of three feet 
in length, one end of which has been cut to the screw of the bottle. This 
pipe may be bent like a in the figure, if the bottle is to be heated in an open 
fire or in a furnace open at the top. From 3 to 9 pounds of the oxide may be 
introduced as a charge, according to the quantity of gas to be prepared, each 
pound of the best Exeter manganese yielding about 1400 cubic inches, or 

Fig. 69. 




(O 



5.05 gallons of gas. Upon the first application of heat, water comes ofT, as 
steam, mixed with a gas which extinguishes flame; this is owing to the impu- 
rity of the oxide. The products may be allowed to escape, till the point of a 
wood-match red without flame, applied to the orifice, is not completely extin- 
guished, but rekindled and made to burn with brilliancy; the gas is then suffi- 
ciently pure, and means must be taken for collecting it. A small flexible lead 
tube b, of any convenient length is adapted to the iron pipe, by means of a 
perforated cork, by which the gas is conveyed to a pnuematic trough, and col- 
lected in glass jars filled with water, as in the former experiment; or, as this 
process affords considerable quantities of oxygen, the gas is more generally 
conducted into the inferior cylinder or drum of a copper gas holder c, full of 
water. The water does not flow out by the recurved tube which forms the 
lower opening, but is retained in the vessel by the pressure of the atmosphere 
on the surface of the water in that tube, as water is retained in a bird's drink- 
ing glass. But when the lead tube is introduced into the gas-holder by this 
opening, water escapes by it, in proportion as gas is thrown into the cylinder, 
and rises in bubbles to the top. The progress of filling the gas-holder may be 
observed by the glass gauge tube £*, which is open at both ends, and connected 
with the top and bottom of the cylinder, so that the water stands at the same 
height in the tube as in the cylinder. Convenient dimensions for the cylinder 



1S8 



OXYGEN. 



itself are 16 inches in height by 12 in diameter; to fill which a charge of three 
pounds of manganese may be used. The gauge tube is so apt to be broken, or 
to occasion leakage at its junctions with a cylinder, when the latter is large and 
unwieldy, that it is generally better to forego the advantage it offers, and dis- 
pense with this addition to the gas-holder. When applied to a small gas- 
holder, the ends of the tube are conveniently adapted to the openings of the 
cylinder, by means of perforated corks, which are afterwards covered with 
melted sealing wax. 

After the cylinder is filled, the lower opening by which the gas was ad- 
mitted is closed by a good cork, or by a brass cap made to screw over it. The 
superior cylinder is an open water trough, connected with the inferior cylinder 
by two tubes provided with stopcocks, m and n, one of which m is continued 
to the bottom of that vessel, and conveys water from the superior cylinder, 
while the other tube n, terminates at the top of the inferior cylinder, and af- 
fords a passage by which the gas can escape from it; when water is allowed to 
descend by the other tube. The tube and perforation of the stopcock of m 
should be considerably wider than n. A jar a is filled with gas by inverting 
Fig. 70. ^ ^ u ^ °^ water m tne superior cylinder, over the opening of n, 
as exhibited in the figure, and allowing the gas to ascend from 
the inferior cylinder. Gas may likewise be obtained by the 
stopcock / (Figure 69) water being allowed to enter by m at the 
same time. 

Oxygen may likewise be disengaged from oxide of manganese 
in a flask or retort, by means of sulphuric acid diluted with an 
equal bulk of water, but this is not a process to be recommended. 
When only a small quantity of oxygen is required, it is bet- 
ter to have recourse to chlorate of potash, which has also the ad- 
vantage of giving a perfectly pure gas. 
3°. A well cleansed Florence oil flask, the edges of the mouth of which 
have been heated and turned over so as to form a lip, with a bent glass tube 
and perforated cork fitted to it, as in the figure, forms a convenient retort in 
which about half an ounce of chlorate of potash may be heated by means of 
the Argand spirit lamp. The salt melts, although it contains no water, and 




Fig. 



when nearly red hot, emits abun- 
dance of oxygen gas. At one 
point of the decomposition, the 
effervescence may become so 
violent as to burst the flask, es- 
pecially if the exit tube be nar- 
row, unless the heat be mode- 
rated. The chlorate of potash 
parts with all the oxygen it pos- 
sesses, which amounts to 37 per 
cent, of its weight, and leaves a 
white hard salt, the chloride of 
potassium. From an atomic 
statement of the composition of 
this salt, one equivalent of it 
(1532 parts) will be observed to contain six equivalents of oxygen (600 parts,) 
five in the chloric acid and one in the potash, the whole of which come off, 
leaving an equivalent of chloride of potassium (932 parts:) — 

KO + C10 5 =$|° cl 




OXYGEN. 189 

Half an ounce of chlorate of potash should yield 270 cubic inches or nearly 
a gallon of pure oxygen gas.* 

Properties. — Oxygen gas is colourless, and destitute of odour and taste. It 
is heavier than air in the ratio of 1102.6 to 1000 according the weighings of 
Dulong and Berzelius; 100 cubic inches of air being taken to weigh 31 grains 
at the temperature of 60° and with the barometer at 30 inches, 100 cubic inches 
of oxygen gas will therefore weigh 34.18 grains. One cubic inch weighs 
0.3418 or very nearly l-3rd of a grain. It has never been liquefied by cold or 
pressure. Oxygen is so sparingly soluble in water, that when agitated in con- 
tact with that fluid no perceptible diminution of its volume takes place. 
But when water is previously deprived of air by boiling, 100 cubic inches of 
it dissolve three and a half cubic inches of this gas. 

If a lighted wax taper attached to a copper wire be blown out, and dipped 
into a vessel of oxygen gas, while the wick remains red hot, it instantly re- 
kindles with a slight explosion, and burns with great brilliancy. If soon 
withdrawn and blown out, it may be revived again in the same manner, and 
the experiment be repeated several times in the same gas. Lighted tinder 
burns with flame in oxygen, and red-hot charcoal with brilliant scintillations. 
Burning sulphur intioduced into this gas in a little hemispherical cup of iron- 
plate with a wire attached to it, burns with an azure blue flame of considerable 
intensity. Phosphorus introduced into oxygen in the same manner, burns 
with a dazzling light of the greatest splendour, particularly after the phos- 
phorus boils and rises through the gas in vapour. Indeed all bodies which 
burn in air, burn with increased vivacity in oxygen gas. Even iron wire may 
be burned in this gas. For this purpose thin harpsichord wire should be 
coiled about a cylindrical rod into a spiral form. The rod being withdrawn, 
a piece of thread must be twisted about one end of the wire, and dipped into 
melted sulphur, the other end of the wire is to be fixed into a cork, so that 
the spiral may hang vertically. The sulphured end is then to be lighted, and 
the wire suspended in ajar of oxygen, open at the bottom, such as that repre- 
sented in Fig. 70, page 188, supported upon an earthenware plate. The wire is 
kindled by the sulphur, and burns with an intense white light, throwing out a 
number of sparks, or occasionally allowing a globule of fused oxide to fall; 
while the wire itself continues to fuse and burn till it is entirely consumed, or 
the oxygen is exhausted. This experiment forms one of the most beautiful 
and brilliant in chemistry. The globules of fused oxide are of so elevated a 
temperature, that they remain red-hot for some time under the surface of wa- 
ter, and fuse deeply into the substance of the stoneware plate upon which they 
fall. 

Oxygen gas is respirable, and indeed is constantly taken into the lungs 
from the atmosphere in ordinary respiration. When a portion of dark blood 
drawn from a vein is agitated with this gas, the colour becomes of a fine vermilion 
red. The same change occurs in the blood of living animals, during respira- 
tion, from the absorption of oxygen gas, which is believed to maintain the 
animal heat in part. A small animal, also, such as a mouse or bird, lives four 
or five times longer in a vessel of oxygen than it will in an equal bulk of air. 
But the continued respiration of this gas in a state of purity is injurious to 
animal life. A rabbit is found to breathe it without inconvenience for some 



* [Perfectly pure oxygen may also be obtained from the red chromate of potassa by the 
action of sulphuric acid. This salt when heated with its own weight of oil of vitriol, is 
decomposed, the acid unites with the base, and forms sulphate of potassa while at the 
same time, the chromic acid loses one half of its oxygen and is reduced to protoxide 
which also unites with sulphuric acid forming sulphate of the protoxide of chromium.— 
Annals of Elect, and Magnetism, Sept. 1842. R. B.] 



190 



OXYGEN. 



time, but after an interval of an hour or more, the circulation and respiration 
are much quickened; and a state of great excitement of the general system 
supervenes; this is by and by followed by debility, and death occurs in from 
six to ten hours. The blood is found to be highly florid in the veins as well 
as the arteries, and the heart, according to Broughton, continues to act strongly 
after the breathing has ceased. 

Oxygen may be made to unite with all the other elements except fluorine, 
and forms oxides, while the process of uniting with oxygen is termed oxida- 
tion. With the same element oxygen often unites in several proportions, 
forming a series of oxides, which are then distinguished from each other by 
the different prefixes enumerated under chemical nomenclature (page 89.) 
Many of its compounds are acids, particularly those which contain more than 
one equivalent of oxygen to one of the other element, and compounds of this 
nature are those which it most readily forms with the non-metallic elements, 
such as carbonic acid with carbon, sulphurous acid with sulphur, phosphoric 
acid with phosphorus. But oxygen unites in preference with single equiva- 
lents of a large proportion of the metallic class of elements, and forms bodies 
which are alkaline or have the character of bases, such as potash, lime, mag- 
nesia, protoxide of iron, &c. A certain number of its compounds are neither 
acid nor alkaline, and are therefore called neutral bodies, such as the oxide of 
hydrogen or water, carbonic oxide, and nitrous oxide. The greater number of 
these neutral oxides are also protoxides. 

It has already been stated that in a classification of the elements oxygen 
does not stand alone, but forms one of a small natural family along with sul- 
phur, selenium and tellurium (page 119.) These elements also form acid, 
basic and neutral classes of compounds, with the same bodies as oxygen does, 
of which the sulphur compounds are well known, and always exhibit a well- 
marked analogy to the corresponding oxides. Oxygen acid unite with oxy- 
gen bases, and form neutral salts, so do sulphur acids with sulphur bases, 
selenium acids with selenium bases, and tellurium acids with tellurium bases. 

The combinations of oxygen, like those of all other bodies, are attended 
with the evolution of heat. This result, which is often overlooked in other 
combinations, in which the proportions of the bodies uniting and the pro- 
perties of their compounds receive most attention, assumes an unusual degree 
of importance in the combinations of oxygen. The economical applications 
of the light and heat evolved in these combinations are of the highest conse- 
quence and value, and oxidation alone of all chemical actions is practised, not 
for the value of the products it affords, and indeed without reference to them, 
but for the sake of the incidental phenomena attending it. Of the chemical 
combinations too, which we habitually witness, those of oxygen are infinitely 
the most frequent, which arises from its constant presence and interference, as 
a constituent of the atmosphere. Hence, when a body combines with oxy- 
gen, it is said to be burned; and instead of undergoing oxidation, it is said to 
suffer combustion; and a body which can combine with oxygen and emit heat 
is termed a combustible. Oxygen, in which the body burns, is then said to 
support combustion, and called a supporter of combustion. 

The heat evolved in combustion is definite, and can be measured. With 
this view, it is employed to melt ice, to raise the temperature of water from 
32° to 212°, or to convert water into steam, and its quantity estimated by the 
extent to which it produces these effects. The heat from the oxidation of a 
combustible body is thus found to be as constant as any other of its properties. 
Despretz obtained, by such experiments, the results contained in the follow- 
ing table: — 



OXYGEN. 191 

HEAT FROM COMBUSTION. 

] pound of pure charcoal .... heats from 32o to 212° , 78 lbs. of water 

„ ,, charcoal from wood ... „ „ „ 75 

„ „ baked wood .... „ „ „ 36 

„ „ wood containing 20 percent, of water . „ „ „ 27 

„ „ bituminous coal ' . . . . „ „ ..60 

„ „ turf „ „ „ 25 to 30 

„ „ alcohol ..... „ „ „ 67.5 

„ „ olive oil, wax, &c. ... „ „ „ 90 to 95 

„ „ ether „ 80 

„ „ hydrogen ..... „ „ „ 236.4 

The quantity of heat evolved appears to be connected with the proportion 
of oxygen consumed, for the greater the weight of oxygen with which a pound 
of any combustible unites, the more heat is produced. The following results 
indicate that the heat depends exclusively upon the oxygen consumed, four 
different combustibles in consuming a pound of oxygen affording nearly the 
same quantity of heat: — 

HEAT FROM COMBUSTION. 

1 pound of oxygen with hydrogen heats from 32° to 212°, 29£ lbs. of water. 
„ „ with charcoal „ „ „ . 29 „ „ 

„ with alcohol „ „ „ 23 „ 

„ „ with ether „ „ „ 28£ „ „ 

The quantity of combustible consumed in these experiments varied conside- 
rably, but the oxygen being the same, the heat evolved was nearly the same 
also. But when the same quantity of oxygen converted phosphorous into 
phosphoric acid, exactly twice as much heat was evolved, according to Des- 
pretz, as in the former experiments. It is doubtful whether these observations 
will had to any general conclusions; but it is certain that the coincidences 
which they exhibit merit attention. The superior vivacity of the combustion 
of these and other bodies in pure oxygen, compared with air, depends entirely 
upon the increased rapidity of the process, and the larger quantity of combus- 
tible oxidated in a given time. A candle burns with more light and heat in 
oxygen than in air, but it consumes proportionally faster. 

Oxidation is often a very slow process and imperceptible in its progress, as 
in the rusting of iron and tarnishing of lead exposed to the atmosphere. The 
heat being then evolved in a very gradual manner is dissipated and never accu- 
mulates. But when the oxide formed is the same, the nature of the change 
affected is no way altered by its slowness. Iron oxidates rapidly when intro- 
duced in a state of ignition into oxygen gas, and lead, in the form of the lead 
pyrophorus, which contains that metal in a state of high division, takes fire 
spontaneously and burns in the air, circumstances then favouring the rapid 
progress of oxidation. 

Oxidation may also go on with a degree of rapidity sufficient to occasion a 
sensible evolution of heat, but without flame and open combustion. The ab- 
sorption of oxygen by spirituous liquors in becoming acetic acid, and by many 
other organic substances, is always attended with the production of heat. The 
smouldering combustion of iron-pyrites and some other metallic ores in the at- 
mosphere, is a phenomenon of the same nature. Most bodies which burn 
with flame, also admit of being oxidated at a temperature short of redness, 
and exhibit the phenomenon of low combustion. Thus, tallow thrown upon 
an iron plate not visibly red-hot, melts and undergoes oxidation, diffusing a 
pale lambent flame only visible in the dark (Dr. C. J. B. Williams.) If the 
tallow be heated in a little cup with a wire attached, till it boils and catches 
fire, and the flame then be blown out, the hot tallow will still continue in a 
state of low combustion, of which the flame may not be visible, but which is 
sufficient to cause the renewal of the high combustion, if the cup is imme- 



192 OXYGEN. 

diately introduced into a jar of oxygen gas. A candle newly blown out is 
sometimes rekindled in oxygen, although no point of the wick remains red, 
owing to the continuance of this low combustion. When a coil of thin plati- 
num wire, or a piece of platinum foil is first heated to redness and then held 
over a vessel containing ether or hot alcohol, the vapours of these substances, 
mixed with the air, oxidate upon the hot metallic surface, and may sustain the 
metal at a red heat for a long time, without the occurrence of combustion with 
flame. The product, however, of the low combustion of these bodies is pe- 
culiar, as is obvious from its pungent odour. 

Combustion in air. — The affinity for oxygen of all ordinary combustibles 
is greatly promoted by heating them, and is indeed rarely developed at all ex- 
cept at a high temperature. Hence to determine the commencement of com- 
bustion, it is commonly necessary that the combustible be heated to a certain 
point. But the degree of heat necessary to inflame the combustible, is in 
general greatly inferior to what is evolved during the progress of the combus- 
tion, so that a combustible, once inflamed, maintains itself sufficiently hot to 
continue burning till it is entirely consumed. Here the difference may be ob- 
served between combustion and simple ignition. A brick heated till it is red- 
hot in a furnace, and taken out, exhibits ignition, but has no means within itself 
of sustaining a high temperature, and soon loses the heat which it had acquired 
in the fire, and on cooling is found unchanged. The oxidable constituents of 
wood, coal, oils, tallow, wax, and all the ordinary combustibles are the same, 
carbon and hydrogen, which in combining with oxygen, at a high tempera- 
ture, always produce carbonic acid and water, which being volatile disappear, 
forming part of the heated aerial column that rises from the burning body. 
The constant removal of the product of oxidation, thus effected by its volatility, 
greatly favours the progress of combustion in such bodies, by permitting the 
free access of air to the unconsumed combustible. The interference of air 
in combustion is obvious from the facility with which a fire is checked or ex- 
tinguished when the supply of air is lessened or withheld, and, on the con- 
trary, revived and animated when the supply of air is increased by blowing 
upon it. For the oxygen of the air being consumed in combining with the 
combustible, a constant renewal of it is necessary. Hence, if a lighted taper, 
floated by a cork upon water, be covered with a bell jar having an opening at 
top, such as that in which the iron-wire was burned, the taper will burn for a 
short time without change, then more and more feebly, in proportion as the 
oxygen is exhausted, and at last will expire. The air remaining in the jar is 
no longer suitable to support combustion, and a second lighted taper intro- 
duced into it by the opening at top, is immediately extinguished. 

In combustion, no loss whatever of ponderable matter occurs; nothing is 
annihilated. The matter formed may always be collected without difficulty, 
and is found to have exactly the weight of the oxygen and combustible together 
which have disappeared. The most simple illustrations of this fact are obtained 
in the combustion of those bodies, which afford a solid product. Thus when 
2 grains of phosphorus are kindled in a measured volume of oxygen gas, they 
are found converted after combustion into a quantity of white powder (phos- 
phoric acid,) which weighs 4i grains, or the phosphorus acquires 2§ grains; 
at the same time Ih. cubic inches of oxygen disappear which weigh exactly 
2| grains. In the same way when iron wire is burned in oxygen, the weight 
of solid oxide produced is found to be equal to that of the wire originally em- 
ployed added to that of the oxygen gas which has disappeared. But the oxi- 
dation of mercury affords a more complete illustration of what occurs in 
combustion. Exposed to a moderate degree of heat for a considerable time 
in a vessel of oxygen, that metal is converted into red scales of oxide, which 
possess the additional weight of a certain volume of oxygen which has dis- 



COMEUSTION IN AIR. 193 

appeared. But if the oxide of mercury, so produced, be then put into a small 
retort, and reconverted by a red heat into oxygen and fluid mercury, the quan- 
tity of the oxygen emitted is found to be the same as had combined with the 
mercury in the first part of the operation, thus proving that oxygen is really 
present in the oxidized body. 

The evolution of heat, which is the most striking phenomenon of combus- 
tion, still remains to be accounted for. It has been referred to the loss of 
latent heat by the combustible and oxygen, when, from the condition of gas 
or liquid, they become solid after combustion; to a reduction of capacity for 
heat, the specific heat of the product being supposed to be less than that of the 
bodies burned; to a discharge of the electricities belonging to the different 
bodies, occurring in the act of combination. But the first two hypotheses 
are manifestly insufficient, and the last is purely speculative. The evolution 
of heat during intense chemical combination, such as oxidation, may be re- 
ceived at present as an ultimate fact; but if we choose to go beyond it, w r e may 
suppose that the heat exists in a combined and latent state in either the oxy- 
gen or combustible, or in both, that each of these bodies is a compound of its 
material bases with heat, the whole or a definite quantity of which they throw 
off on combining with each other. Heat, like other material substances, is 
here supposed, not to evince its peculiar properties while in a state of com- 
bination with other matter, but only when isolated and free. This view gives 
a literal character to the expressions, liberation, disengagement, and evolution 
of heat during combustion. The phenomenon, it is to be remembered, is not 
confined to oxidation, but occurs in an equal degree in combinations without 
oxygen, and indeed to a greater or less extent in all chemical combinations 
whatever. 

Uses. — Pure oxygen has not as yet found any considerable application in the 
arts. But by the chemist it is applied to support the combustion of hydrogen 
gas, in producing intense heat. A more considerable application of it is likely 
to arise in the combustion of oil in the lamp of Mr. Gurney, to produce an 
intense light suitable for marine light-houses. In this lamp, which is an Ar- 
gand with several concentric wicks, oxygen gas from a gasometer is admitted 
into the centre of the flame, and is found to produce so much more light than 
air does, from the combustion of the same quantity of oil, as fully to compen- 
sate for the cost of the oxygen. "Where a large quantity of oxygen is required, 
as in this application of it, the gas may be obtained by heating oxide of man- 
ganese in a cylinder of cast iron supported over a furnace, like the retort for 
coal gas. The calcined oxide does not regain its oxygen when afterwards 
exposed to the air, as was once supposed, but would still be of some value in 
the preparation of chlorine. 



SECTION II. 

HYDROGEN. 

Equivalent 12.5 (oxygen 100,) or 1 as the basis of the hydrogen scale; 
symbol H; density 69 (air 1000;) combining measure f ~| (tivo volumes.) 

Hydrogen gas, which was long confounded with other inflammable airs, 

was first correctly described by Cavendish, in 1766. It does not exist un- 

combined in nature, at least the atmosphere does not contain any appreciable 

proportion of hvdrogen. But it is one of the elements of water, and enters 

17 



194 



HYDROGEN. 



into nearly every organic substance. Its name is derived from v}»p, water, 
and yeimofj I generate, and refers to its forming water when oxidated. 

Preparation. — This element, although resembling oxygen in being a gas, 
appears to be more analogous to a metal in its chemical properties. By heat- 
ing oxide of mercury, we have seen it resolved into oxygen and mercury; and 
several other metallic oxides, such as those of silver and gold, are susceptible 
of a similar decomposition. But some others are deprived of only a portion 
of their oxygen by the most intense heat, such as peroxide of manganese; and 
many, such as the protoxide of lead, are not decomposed at all by simple cal- 
cination. By igniting the latter oxide, however, mixed with charcoal, its oxy- 
gen goes off in combination with carbon, as carbonic oxide, and the lead is 
left. The oxide of hydrogen or water is in the same case. Heat alone does 
not decompose it But potassium and sodium brought into contact with it, at 
the temperature of the air, combine with its oxygen, and are converted into 
the oxides potash and soda; and hydrogen is consequently liberated, water 
being the oxide of hydrogen. 

Iron and many other metals decompose water, and become oxides, at a red 
heat. Hence, hydrogen gas is sometimes procured by transmitting steam 
through an iron tube placed across a furnace and heated red-hot. Some other 

Fig. 72. 




compounds of hydrogen are decomposed more easily than water, by iron and 
zinc. The chloride of hydrogen or hydrochloric acid is decomposed by these 
metals, and evolves hydrogen, at the ordinary temperature of the air. But 
this gas is more generally obtained by putting pieces of zinc or iron into oil 
of vitriol or the concentrated sulphuric acid, diluted with 6 or 8 times its bulk 
of water. The hydrogen is then derived from the decomposition of the pro- 
portion of water intimately united with the acid, as illustrated in the following 
diagram, zinc being used, and the quantities expressed: 




After decomposition. 
12£ hydrogen. 



1004 sulphate of oxide of 



-zinc. 



Before decomposition. 

6131 oil of vitriol, f Hydrogen 12 

or sulphate -< Oxygen 100 

of water. (^ Sulphuric acid 501 
403 zinc . . . Zinc . . 403 

10161 1016^ 10161 

Or by symbols: — 

H + S 3 and Z = Z O-f S 3 and H. 

The zinc dissolves in the acid with effervescence, from the escape of hydro- 
gen gas. It will be observed that the products after decomposition, mentioned 
in the last column, hydrogen and sulphate of oxide of zinc are similar to those 
before decomposition, in the first column, zinc and sulphate of water; and 
that the change occurring is simply the substitution of zinc for hydrogen in 
the sulphate of water. The large quantity of water used with the acid is use- 
ful to dissolve the sulphate of zinc formed. 



HYDROGEN. 



195 



Zinc is generally preferred to iron, in the preparation of hydrogen, and is 
previously granulated, by being fused in a stone-ware crucible, and poured into 
water; if sheet zinc be used, it must be cut into small pieces. The common 
glass retort may be used in the experiment, or a gas-bottle, such as the half 
pound phial (Fig. 73,) with a cork having two perforations fitted with glass 



Fig. 73. 




tubes, one of which descends to the bottom 
of the bottle, and is terminated externally by 
a funnel for introducing the acid, whilst the 
other is the exit tube, by which the hydro- 
gen escapes. With an ounce or two of zinc 
in it, the bottle is two-thirds filled with wa- 
ter, and the undiluted acid added from time 
to time by the funnel, so as to sustain a con- 
tinued effervescence. No gas escapes by 
the funnel tube, as its extremity within the 
bottle is always covered by the fluid.. To 
produce large quantities, a half-gallon stone- 
ware jar may be mounted as a gas-bottle, 
with a flexible metallic pipe fitted to the 
cork, as the exit tube. This gas may be 
collected, like oxygen, either in jars over 
the pneumatic trough, or in the gas-holder. 
The first jar or two filled will contain the air of the gas-bottle, and therefore 
must not be considered as pure hydrogen. One ounce of zinc is found to 
cause the evolution of 615 cubic inches of hydrogen. 

Properties. — Hydrogen gas thus prepared is not absolutely pure, but contains 
traces of sulphuretted hydrogen and carbonic acid, which may be removed by 
agitating the gas with lime-water or caustic alkali. It has also a particular 
odour, which is not essential to hydrogen, as the gas evolved from the amalgam 
of sodium, acted on by pure water without acid, is perfectly inodorous. An 
oily compound of carbon and hydrogen, which appears to be the cause of this 
odour, may be separated in a sensible quantity from the gas prepared by iron, 
by transmitting it through alcohol. Of the pure gas, water does not dissolve 
more than lg per cent, of its bulk. Hydrogen has never been liquefied by cold 
or pressure. 

Hydrogen is the lightest substance in nature, being sixteen times lighter 
than oxygen, and 14.4 times lighter than air; 100 cubic inches of it weigh only 
2.14 grains. Soap bubbles blown with this gas ascend in the atmosphere; and 
it is used, as is well known, to inflate balloons, which begin to rise when the 
weight of the stuff of which they are made and the hydrogen together, are less 
than the weight of an equal bulk of air. A light bag is prepared for making 
this experiment in the chamber, by distending the lining membrane of the crop 
of the turkey, which may weigh 35 or 36 grains, and when filled with hydrogen, 
about 5 grains more, or 41 grains ; the same bulk of air, however, would weigh 
50 or 51 grains; so that the little balloon when filled with hydrogen has a 
buoyant power of 9 or 10 grains. Sounds produced in this gas were found by 
Leslie to be extremely feeble, much more feeble indeed than its rarity compared 
with air could account for. Hydrogen may be taken into the lungs without 
inconvenience, when mixed with a large quantity of air, being in no way dele- 
terious; but it does not, like oxygen, support respiration, and therefore an animal 
placed in pure hydrogen soon dies of suffocation. A lighted taper is extinguished 
in this gas. 

Hydrogen is eminently combustible, and burns when kindled in the air with 
a yellow flame of little intensity, which moistens a dry glass jar held over it ; 
the gas combining with the oxygen of the air in burning, and producing water 



196 HYDROGEN. 

/ 

If before being kindled the gas is first mixed with enough of air to burn it com- 
pletely, or with between two and three times its volume, and then kindled, the 
combustion of the whole hydrogen is instantaneous and attended with explosion. 
With pure oxygen instead of air the explosion is much more violent, particularly 
when the gases are mixed in the proportions of two volumes of hydrogen to one 
of oxygen, which are the proper quantities for combination. The combustion 
is not thus propagated through a mixture of these gases, when either of them is 
in great excess. The sound in such detonations is occasioned by the concussion 
which the atmosphere receives from the sudden dilatation of gaseous matter, in 
this case of steam, which is prodigiously expanded from the heat evolved in its 
formation. A musical note may be produced by means of these detonations, 
when they are made to succeed each other very rapidly. If hydrogen be gene- 
rated in a' gas bottle, and kindled as it escapes from an upright glass jet having 
a small aperture, the gas will be found to burn tranquilly ; but on holding an 
open glass tube of about two feet in length over the jet, like a chimney, the 
flame will be elongated and become flickering. A succession of little detona- 
tions is produced, from the gas being carried up and mixing with the air of the 
tube, which follow each other so quickly as to produce a continuous sound or 
musical note. 

Several circumstances affect the combination of hydrogen with oxygen, which 
are important. These gases may be mixed together in a glass vessel, and pre- 
served for any length of time without combining. But combination is instantly 
determined by flame, by passing the electric spark through the mixture, or even 
by introducing into it a glass rod, not more than just visibly red-hot. Hydro- 
gen, indeed, is one of the more easily inflammable gases. If the mixed gases be 
heated in a vessel containing a quantity of pulverized glass, or any sharp pow- 
der, they begin to unite in contact with the foreign body in a gradual manner 
without explosion, at a temperature not exceeding 660°. The presence of me- 
tals disposes them to unite at a still lower temperature ; and of the metals, those 
which have no disposition of themselves to oxidate, such as gold and* platinum, 
occasion this slow combustion at the lowest temperature. In 1824, Dobereiner 
made the remarkable discovery that newly prepared spongy platinum has an 
action upon hydrogen independently of its temperature, and quickly becomes 
red-hot when a jet of this gas is thrown upon it in air, combination of the gases 
being effected by their contact with the metal. In consequence of this ignition 
of the platinum the hydrogen itself is soon inflamed, as it issues from the jet. 
An instrument depending upon this action of platinum has been constructed for 
producing an instantaneous light. More lately Mr. Faraday observed that the di- 
vided state of the platinum, although favourable, is not essential to this action ; and 
that a plate of that metal, if its surface be scrupulously clean, will cause a combina- 
tion of the gases, accompanied with the same phenomena, as the spongy platinum. 
This action of platinum is manifested at temperatures considerably below the 
freezing point of water, and in an explosive mixture largely diluted with air or 
hydrogen. Spongy platinum, made into pellets with a little pipe-clay, and dried, 
when introduced into mixtures of oxygen and hydrogen, will be found to cause 
a gradual and silent combination of the gases, in whatever proportions they are 
mingled, which will not cease till one of them is completely exhausted. The 
theory of this effect of platinum is very obscure. It belongs to a class of actions 
depending upon surface, not confined to that metal, and by which other com- 
bustible vaporous bodies are affected besides hydrogen (page 156.) 

The flame of hydrogen, although so slightly luminous, is intensely hot ; few 
combinations producing so high a temperature, as the combustion of hydrogen. 
In the oxi-hydrogen blow-pipe, oxygen and hydrogen gases are brought by tubes 
from different gas-holders, and allowed to mix immediately before they escape 
by the same orifice, at which they are inflamed. This is most safely effected 



WATER. 197 

by fixing a jet for the oxygen within the jet of hydrogen, so that the oxygen is 
introduced into the middle of the flame of hydrogen, a construction first pro- 
posed by Mr. Maugham, and adopted to the use of coal gas instead of hydrogen 
by Mr. Daniel].* At this flame the most refractory substances, such as pipe-clay, 
silica and platinum, are fused with facility, and the latter even dissipated in the 
state of vapour. The flame itself owing to the absence of solid matter, is scarce- 
ly luminous, but any of the less fusible earths, upon which it is thrown, a mass 
of quick-lime for instance, is heated most intensely, and diffuses a light, which 
for whiteness and brilliancy may be compared to that of the sun. With a requi- 
site supply of the gases this light may be sustained for hours, care being taken 
to move the mass of lime slowly before the flame, so that the same surface may not 
be long acted upon ; for the high irradiating power of the lime is soon impaired, 
it is supposed from a slight agglutination of its particles occasioned by the heat. 
This light placed in the focus of a parabolic reflector, was found to be visible, in 
the direction in which it was thrown, at a distance of 69 miles, in one experi- 
ment made by Mr. Drummond, when using it as a signal light. The heating 
effects are even more intense when the gases are forced into a common recep- 
tacle, and allowed to escape from under pressure, but there is the greatest risk 
of the flame passing back through the exit tube and exploding the mixed gases, .an 
accident which would expose the operator to the greatest danger. Mr. Hem- 
ming's apparatus, however, may be used without the least apprehension. A 
common bladder is used to hold the mixture, and the gas before reaching the 
jet, at which it is burned is made to pass through his safety tube. This consists 
of a brass cylinder about six inches long and 3-4ths of an inch wide, filled with 
fine brass wire of the same length, which is tightly wedged by forcibly inserting 
a pointed rod of metal into the centre of the bundle. The conducting power of 
the metallic channels through which the gas has then to pass, is so great as com- 
pletely to intercept the passage of the flame. 

Hydrogen is capable of forming two compounds with oxygen, namely, 
water, which is the protoxide, and the peroxide of hydrogen. 

Uses. — The most important of the present applications of hydrogen gas is 
in the oxi-hydrogen blow-pipe. It has been superseded as a material for in- 
flating balloons, by coal gas, the balloon being proportionally enlarged to com- 
pensate for the less buoyancy of the latter gas. 



PROTOXIDE OF HYDROGEN.— WATER. 

Equivalent 112.5, or 9 on hydrogen scale; formula H-fO, or HO; den- 
sity 1, as steam 620.2 (air 1000;) combining measure of steam { ]]• 



Mr. Cavendish first demonstrated, in 1781, that the product of the combus- 
tion of hydrogen and oxygen is water. He burned known quantities of these 
gases in a dry glass vessel, and found that water was formed in quantity ex- 
actly equal to the weights of the gases which disappeared. It was afterwards 
established by Humboldt and Gay-Lussac, that the gases unite rigorously in 
the proportion of two volumes of hydrogen to one volume of oxygen, and that 
the water produced by their union occupies, while it remains in the state of 
vapour, exactly two volumes (page 111.) The proportion of the constituents 
of water by weight was determined with extraordinary care by Berzelius and 
Dulong. Their method was to transmit dry hydrogen gas over a known 
weight of the black oxide of copper, contained iu a glass tube, and headed to 

* Phil. Mag. 3rd Series, vol. II. p. 57. 
17* 



198 HYDROGEN. 

redness by a lamp. The gas was afterwards conveyed through another 
weighed tube containing the hygrometric salt, chloride of calcium. The hy- 
drogen gas in passing over the oxide of copper, combines with its oxygen and 
forms water, which is carried forward by the excess of hydrogen gas, and 
absorbed in the chloride of calcium tube. The weight of this water being 
ascertained, the proportion of oxygen it contains is determined by ascertaining 
the loss which the oxide of copper has sustained; the difference is the hydro- 
gen. The mean of three such experiments gave as the composition of water: 

Oxygen - 88.9 or 100 or 8.009 

Hydrogen - 11.1 " 12.48 " 1. 



100 112.48 9.009 

The oxygen and hydrogen are therefore very nearly, if not exactly, in the 
proportion of 8 to 1, as appears by the proportions of the last column. This 
experiment serves not only to determine rigorously the composition of water, 
but it offers also the best method of ascertaining the composition of such me- 
tallic oxides as are de-oxygenated by hydrogen. 

Properties. — When cooled down to 32° water freezes, if in a state of agita- 
tion, but may retain the liquid condition at a lower temperature, if at rest 
(page 50;) the ice, however, into which it is converted cannot be heated above 
32° without melting. Ice is lighter than water, its specific gravity being 
0.916; and the form of its crystal is a rhomboid, very nearly resembling ice- 
land spar. Water is elastic and compressible, yielding according to Oersted 
53 millionths of its bulk to. the pressure of the atmosphere, and, like air, in 
proportion to the compressing force for different pressures. The peculiarities 
of its expansion by heat while liquid, have already been fully described (page 
30.) Under a barometric pressure of 30 inches, it boils at 212°, but evaporates 
at all inferior temperatures. Its boiling point is elevated by the solution of 
salts in it, and the temperature of the steam from these solutions is not con- 
stantly 212°, as has been alleged, but that of the last strata of liquid through 
which the steam has passed. When mixed with air, the vapour of water has 
a tendency to condense in vesicles, which enclose air; forming in this condi- 
tion the masses of clouds which remain suspended in the atmosphere, from 
the lightness of the vesicles, the substance of mists and fogs, and " vapour" 
generally, in its popular meaning. The vesicles may be observed by a lens 
of an inch focal length, over the dark surface of hot tea or coffee, mixed with 
an occasional solid drop which contrasts with them. According to the expe- 
riments of Saussure, made upon the mists of high mountains, these vesicles 
generally vary in size from the l-4500th to the l-2780th of an inch, but are 
occasionally observed as large as a pea. They are generally condensed by 
their collision into solid drops, and fall as rain; but their precipitation in that 
form is much retarded in some conditions of the atmosphere. 

A cubic inch of water at 62°, Bar. 30 inches, weighs in air 252.458 grains. 
The imperial gallon has been defined to contain 10 pounds avoirdupois (70,000 
grains) of distilled water at that temperature and pressure. Its capacity is there- 
fore 277.19 cubic inches. The specific gravity of water at 60° is 1, being the 
unit to which the densities of all other liquids and solids are conveniently re- 
ferred ; it is 8 1 5 times heavier than air at that temperature. 

In its chemical relations water is eminently a neutral body. Its range of 
affinity is exceedingly extensive, water forming definite compounds, to all of 
which the name hydrate is applied, with both acids and alkalies, with a large 
proportion of the salts, and indeed with most bodies containing oxygen. It is 
also the most general of all solvents. Gay-Lussac has observed that the solution 
of a salt is uniformly attended with the production of cold, whether the salt be 



WATER. 



199 



anhydrous or hydrated, and that on the contrary, the formation of a definite 
hydrate is always attended with heat: a circumstance which indicates an 
essential difference between solution, and chemical combination .* Even the 
dilution of strong solutions of some salts, such as those of ammonia, occasions 
a fall of temperature. The solvent power of water for most bodies increases 
with its temperature. Thus at 57° water dissolves one fourth of its weight of 
nitre, at 92° one half, at 131° an equal weight, and at 212° twice its weight of 
that salt. Solutions of such salts, saturated at a high temperature, deposite 
crystals on cooling. But the crystallization of some saturated solutions is often 
suspended for a time, in a remarkable manner, and afterwards determined by 
slight causes. Thus, if three pounds of crystallized sulphate of soda be dissolved 
in two pounds of water, with the assistance of heat, and the solution be filtered 
while hot, through paper, to remove foreign solid particles, and then set aside in 
a glass matrass, with a few drops of oil on its surface, it may become perfectly 
cold without crystallization occurring. Violent agitation even may not cause 
it to crystallize. But when any solid body, such as the point of a glass rod, or 
a grain of salt, is introduced into the solution, crystals immediately begin to form 
about the solid nucleus, and shoot out in all directions through the liquid. The 
solubility of many salts of soda and lime does not increase with the temperature, 
like that of other salts. 

Water is also capable of dissolving a certain quantity of air and other gases, 
which may again be expelled from it by boiling the water, or by placing it in 
vacuo. Rain-water generally affords 2| per cent, of its bulk of air, in which 
the proportion of oxygen gas is so high as 32 per cent., and in water from 
freshly melted snow 34.8 per cent, according to the observations of Gay-Lussac 
and Humboldt, while the oxygen in atmospheric air does not exceed 21 per 
cent. Boussingault finds that the quantity of air retained by water, at an altitude 
of 6 or 8000 feet, is reduced to one third of its usual proportion. Hence it is 
that fishes cannot live in Alpine lakes, the air contained in the water not being 
in adequate quantity, for their respiration. The following table exhibits the 
absorbability of different gases by water deprived of all its air by ebullition: 

100 cubic inches of water at 60° and 30 Bar., absorb of 







Dalton and Henry. 


Saussure 


Sulphuretted hydi 


•ogen . 


100 C.I. 


253 


Carbonic acid 




100 


106 


Nitrous oxide 


. , 


100 


76 


Olefiant gas . 


. 


12.5 . 


15.3 


Oxygen 


. 


3.7 . 


6.5 


Carbonic oxide 


. 


1.56 . 


6.2 


Nitrogen 


. 


1.56 . 


4.1 


Hydrogen 


. 


1.56 . 


4.6 



The results of Saussure are probably nearest the truth, for sulphuretted hydrogen 
and nitrous oxide, but for the- other gases those of Dalton and Henry are most 
to be depended on. 

Uses. — Rain received after it has continued to fall for some time may be taken 
as pure water, excepting for the air it contains. But after once touching the 
soil, it becomes impregnated with various earthy and organic matters, from 
which it can only be completely purified by distillation. A copper still should 
be used for that purpose, provided with a copper or block tin worm, which is 
not used for the distillation of spirits, as traces of alcohol remaining in the worm 



* An. de Ch. et de Phys. t. 70 p. 407- See also page 146 of this work. 



200 HYDROGEN. 

and becoming acetic acid, cause the formation of acetate of copper, which would 
be washed out and contaminate the distilled water. The use of white lead 
cement about the joinings of the worm is also to be avoided, as the oxide of lead 
is readily dissolved by distilled water. The first portions of the distilled water 
should be rejected, as they often contain ammonia, and the distillation should 
not be carried to dryness. 

Water employed for economical purposes is generally submitted to a more 
simple process, that of filtration, by which it is rendered clear and transparent 
by the removal of matter mechanically suspended in it. Such foreign matter 
may often be removed in a considerable degree by subsidence, on which ac- 
count it is desirable that the water should stand at rest for a time, before being 
filtered. The filtration of liquids generally is effected on the small scale, by 
allowing them to flow through unsized or filter paper, and that of water, on 
the large scale, by passing it through beds of sand. The sand preferred for 
that purpose is not fine, but gravelly, and crushed cinders or furnace clinkers 
may be substituted for it. Its function, as that also of the paper in the che- 
mist's filter, is to act as a support for the finer particles of mud or precipitate 
which are first deposited on its surface, and form the bed that really filters 
the water. When the mud accumulates so as to impede the action of the 
sand filter, the surface of the sand is scraped, and an inch or two of it removed. 
Upward filtration through a bed of sand is sometimes practised, but it has the 
disadvantage that the filter cannot be cleaned in the manner just indicated. 
Filtering under high pressure and with great rapidity has lately been practised 
in a very compact apparatus, consisting of a box, not above three feet square, 
filled with sand. This filter which becomes speedily choked with the mud it 
detains, is cleansed by suddenly reversing the direction in which the water is 
passing through the box, which occasions a shock that has the effect of loosen- 
ing the sand, and allowing the water to bring away the mud. The action of 
such a filter, lately erected at the Hotel-Dieu of Paris, has been favourably re- 
ported on by M. Arago.* 

Matter actually dissolved in water is not affected by filtration. No repeti- 
tion of the process would withdraw the salt from sea-water and make it fresh. 
Hence the impregnation of peaty matter, which river water generally contains, 
and to the greatest extent in summer, w r hen the water is concentrated by eva- 
poration, is not removed by filtering. Animal charcoal is the proper substance 
for discolouring liquids, as it withdraws organic colouring matter, even when 
in a state of solution. 

In the process of clarifying liquors, by dissolving in them the white of egg 
and other albuminous fluids, the temperature is raised so as to coagulate the 
albumen, which thus forms a delicate net-work throughout the liquid, and is 
afterwards thrown up as scum in the boiling, carrying all the foreign matter 
suspended in the liquid along with it. 

The most usual earthy impurities in water, occasioning its hardness, are 
sulphate of lime, and the carbonate of lime dissolved in carbonic acid, both of 
which are precipitated on boiling the water, and occasion an earthy incrusta- 
tion of the boiler. When waters contain iron, they are termed chalybeate,- 
this metal is most frequently in the state of carbonate dissolved in carbonic 
acid, and rarely in a proportion exceeding one grain in a pound of water. 
The sulphureous waters, which are recognised by their peculiar odour, and 
by blackening silver and salts of lead, contain sulphuretted hydrogen gas, in 
a proportion not exceeding the usual proportion of air in spring water, and no 
oxygen. Saline waters, for the most part contain various salts of lime and 
magnesia, and generally common salt. Their density is always considerably 



* An de Ch. et de Ph. t. 65, p. 428. 



PEROXIDE OF HYDROGEN. 



201 



higher than that of pure water. Sea-water contains 3| per cent, of saline 
matter, and has a density 1.0274. Its composition is interesting, as the sea 
comes to be the grand depository of all the soluble matter of the globe. A 
most minute and valuable analysis of the water of the English Channel has 
lately been executed by Dr. Shweitzer of Brighton; the particulars of which 
I subjoin in contrast with an analysis of the water of the Mediterranean by 
M. Laurens: — 



Sea-water of the English Channel. 

Grains. 

Water 

Chloride of sodium 

potassium 

magnesium 



Of the Mediterranean. 



Bromide of magnesium 
Sulphate of magnesia . 

lime . 

Carbonate of lime 



964.74372 
27.05948 
0.76552 
3.66658 
0.02929 
2.29578 
1.40662 
0.03301 



Carb. of lime & magnesia 



Grains. 

959.26 

27.22 

0.01 

6.14 

7.02 
0.15 
0.20 

1000.00 



1000.0000 

These analyses show that the channel water contains 9 times as much lime as 
the Mediterranean, but this can be accounted for, as the water flows over a bed 
of chalk. The Mediterranean, again, contains twice as much magnesia and 
sulphuric acid as the Channel. In addition to those constituents, distinct 
traces of iodine and of ammonia were detected.* 



PEROXIDE OF HYDROGEN. 

Equivalent, 212.5, or 17 on hydrogen scale; formula H + 2°> °r H0 2 . 

The second compound of hydrogen and oxygen is a liquid, containing twice 
as much oxygen as water, and is a body possessed of very extraordinary pro- 
perties. It was discovered by Thenard, in 1818, who prepared it by a long 
and intricate process. 

Preparation. — The formation of the peroxide of hydrogen depends upon the 
existence of a corresponding peroxide of barium. The latter is obtained by 
calcining pure nitrate of barytes at a high temperature in a porcelain retort, 
and afterwards exposing the earth barytes or protoxide of barium, which is 
left, in a porcelain tube heated to redness, to a stream of oxygen gas, which 
the protoxide rapidly absorbs becoming peroxide. Treated with a little water 
the peroxide of barium slakes and falls to powder, forming a hydrate, of which 
the formula is Ba0 2 -f HO. Dilute acids have a peculiar action upon this 
hydrate, which will be easily understood, if the peroxide of barium is repre- 
sented as the protoxide united with an additional equivalent of oxygen, or as 
BaO-fO. They combine with the protoxide of barium, forming salts of 
barytes, and the second equivalent of oxygen, instead of being liberated in con- 
sequence, unites with the water of the hydrate, the HO of the preceding for- 
mula, giving rise to HO 4-0 or the peroxide of hydrogen, which dissolves in 
the water. Although it would be inconvenient to abandon the systematic name 
peroxide of hydrogen for this compound, still it must be allowed that the pro- 
perties of the body, as well as its mode of preparation are more favourable to 
the idea of its being a combination of water with oxygen, or oxygenated water, 
as it was first named by its discoverer, than a direct combination of its ele- 



* Phil. Mag. 3d Series, vol. 15, page 58. (1839.) 



202 HYDROGEN. 

merits. It is recommended by Thenard to dissolve the peroxide of barium in 
hydrochloric acid considerably diluted with water, and to remove the barytes 
by sulphuric acid, which forms an insoluble sulphate of barytes. The hydro- 
chloric acid, again free in the liquor, is saturated a second time with peroxide 
of barium and precipitated ; and after several repetitions of these two operations, 
the hydrochloric acid itself is removed by the cautious addition of sulphate of 
silver, and the sulphuric acid of the last salt by solid barytes. Such is an out- 
line of the process ; but its success requires attention to a number of minute 
precautions which are fully detailed in the Traite de Chimie of the author 
quoted.* The weak solution of peroxide of hydrogen, which this process 
affords, may be concentrated by placing it with a vessel of strong sulphuric 
acid under the receiver of an air pump, until the solution attains a density of 
1.452, when the peroxide itself begins to rise in vapour without change. It 
then contains 475 times its volume of oxygen. 

M. Pelouze abridges this process considerably by employing hydrofluoric 
acid or fluosilicic acid, in place of hydrochloric acid, to decompose the peroxide 
of barium. By this operation, the barytes separates at once with the acid, in 
the state of the insoluble fluoride of barium, and nothing remains in solution 
but the peroxide of hydrogen. After thus decomposing several portions of 
peroxide of barium successively in the same liquor, the fluoride of barium may 
be separated by filtration, and the peroxide of hydrogen, which is still dilute, 
be concentrated by means of the air-pump. 

Properties. — Peroxide of hydrogen is a colourless liquid resembling water, 
but less volatile, having a metallic taste, and instantly bleaching litmus and 
other organic colouring matters. It is decomposed with extreme facility, effer- 
vescing from escape of oxygen at a temperature of 59°, and when suddenly 
exposed to a greater heat, such as 212°, actually exploding from the rapid evo- 
lution of the gas. It is rendered more permanent by dilution with water, and 
still more so, by the addition of the stronger acids, while alkalies have the oppo- 
site effect. 

The circumstances attending the decomposition of this body are the most 
curious facts in its history. Many pure metals and metallic oxides occasion its 
instantaneous resolution into water and oxygen gas, by simple contact, without 
undergoing any change themselves, affording a striking illustration of catalysis 
(page 156;) and this decomposition may excite an intense temperature, the 
glass tube in which the experiment is made sometimes becoming red-hot. 
Some protoxides absorb at the same time a portion of the oxygen evolved, and 
are raised to a higher degree of oxidation, but most of them do not ; and cer- 
tain oxides, such as the oxides of silver and gold, are reduced to the metallic 
state, their own oxygen going off along with that of the peroxide of hydrogen. 
The decomposition of these metallic oxides cannot be ascribed to the heat 
evolved, for oxide of silver is reduced in a very dilute solution of the peroxide 
of hydrogen, although the decomposition is not then attended with a sensible 
elevation of temperature. The metallic oxides which are decomposed in this 
remarkable manner are originally formed by the decomposition of other com- 
pounds, and not by the direct union of their elements, which in fact exhibit little 
affinity for each other. In this general character, they agree with peroxide of 
hydrogen. 

Uses. — The peroxide of hydrogen is a substance which it is exceedingly de- 
sirable to possess, with the view of employing it in bleaching, and for other 
purposes as a powerful oxidating agent. But the expense and uncertainty of 
the process for preparing this compound have hitherto prevented any applica- 
tion of it in the arts, or even its occasional use as a chemical re-agent. 

* Vol. I, p. 479 of the 6th edition. 



NITROGEN. 203 

SECTION III. 

NITROGEN. 

Synonyme, azote. Equiv. 177, or 14.2 on hydrogen scale; symbol N; 
density 976 ; combining measure Q ^] • 

Dr. Rutherford, of Edinburgh, examined the air which remains after the res- 
piration of an animal, and found that after being washed with lime- water, 
which removes carbonic acid, it was incapable of supporting either combustion 
or respiration. He concluded that it was a peculiar gas. Lavoisier afterwards 
discovered that this gas exists in the air of the atmosphere, forming indeed 
4-5ths of that mixture, and gave it the name azote, (from «, primitive, and £<y>?, 
life,) from its inability to support respiration. It was afterwards named nitrogen 
by Chaptal, because it is an element of nitric acid. Besides existing in air, 
nitrogen forms a constituent of most animal and of several vegetable substances. 
In a natural arrangement of the elements, nitrogen is placed next phosphorus, 
and in close relation with antimony and arsenic. 

Preparation. — Nitrogen is generally procured by allowing a combustible 
body to combine with the oxygen of a certain quantity of air confined in a ves- 
sel. For that purpose a glass flask may be inverted over a small jet of hydro- 
gen, burning as it issues from the upright exit tube of a gas-bottle, till the flame 
goes out, which it does after exhausting the oxygen in the flask. 
The flask is then removed from the hydrogen bottle, its mouth Fig. 74. 
being closed with the thumb, and conveyed to a pneumatic 
trough, where the residuary gas contained in the flask may be 
transferred into a jar. Or a little metallic or porcelain cup may 
be floated, by means of a cork, on the surface of the water-trough. 
A few drops of alcohol are then introduced into the cup, or a 
small piece of phosphorus is placed in it, and being kindled, a 
tall bell jar is held over the cup, with its lip in the water. The 
combustion soon terminates, and the water of the trough rises 
in the jar. Alcohol does not consume the oxygen entirely, a 
small portion of it still remains mingled with the nitrogen ; a cer- 
tain quantity of carbonic acid gas is also produced by its combustion. But the 
combustion of phosphorus exhausts the oxygen completely, and leaves nitrogen 
unmixed with any other gas. Nitrogen may likewise be obtained by several 
chemical decompositions, which, however, are more curious than important as 
sources of this gas. Chlorine gas, for instance, conducted into diluted ammo- 
nia, is absorbed and evolves nitrogen ; so do fragments of sal ammoniac thrown 
into a solution of chloride of lime ; fresh muscular flesh is also dissolved by nitric 
acid when heated, with the evolution of nitrogen. 

Properties. — Nitrogen gas is tasteless and inodorous ; has never been lique- 
fied, and is less soluble in water than oxygen. It is a little lighter than air, 
which possesses the mean density of 79 volumes of nitrogen and 21 volumes of 
oxygen. Nitrogen is a singularly inert substance and does not unite directly 
with any other single element, so far as I am aware, under the influence of 
light or of a high temperature. A burning taper is instantly extinguished in 
this gas, and an animal soon dies in it, not because the gas is injurious, but 
from the privation of oxygen, which is required in the respiration of animals. 
Nitrogen appears to be chiefly useful in the atmosphere, as a diluent of the 
oxygen, thereby repressing to a certain degree the activity of combustion and 
other oxidating processes. The evidence of the fixation of free nitrogen by plants 




204 NITROGEN. 

is incomplete, and therefore it cannot be said with certainty that the nitrogen 
of the organic world is primarily derived from the atmosphere* When heated 
with oxygen, nitrogen does not burn like hydrogen, nor undergo oxidation. 
But nitrogen may be made to unite with oxygen by transmitting several hun- 
dred electric sparks through a mixture of these gases in a tube, with water or 
an alkali present, and nitric acid is produced. The water formed by the com- 
bustion of hydrogen in air, or of a mixture of hydrogen and nitrogen in oxygen, 
has often an acid reaction, which is due to a trace of nitric acid. The same 
acid is also a product of the oxidation of a variety of compounds containing 
nitrogen. Ammonia mixed with air, on passing over spongy platinum at a tem- 
perature of about 572°, is decomposed, and the nitrogen it contains is com- 
pletely converted into nitric acid, by combining with the oxygen of the air. 
Cyanogen and air, under similar circumstances, occasion the formation of nitric 
and carbonic acids.f Nitric acid is also largely produced by the oxidation of 
organic matters during putrefaction in air, when an alkali or lime is present, as 
in the natural nitre soils and artificial nitre beds. 

A suspicion has always existed that nitrogen may be a compound body, but 
it has resisted all attempts to decompose it, and the evidence of its elementary 
character is equally good with that of most other bodies reputed simple. If the 
equivalent of nitrogen be divided by 3, a curious parallellism is observed be- 
tween some of its compounds, and those of oxygen with the same elements, to 
which attention has been directed by ,l M. Laurent and by M. A. Bineau.f 
Before considering the compounds of nitrogen with oxygen, we may notice the 
properties of atmospheric air, which is regarded as a mechanical mixture of 
these gases. 

THE ATMOSPHERE. 

According to the careful experiments of Dr. Prout, 100 cubic inches of atmos- 
pheric air, deprived of aqueous vapour and the small quantity of carbonic acid 
it usually contains, weigh 31.0117 grains, at 60° and 30 Bar. Its density at 
the same temperature and pressure is estimated at 1000, and is conveniently 
assumed as the standard of comparison for the densities of gaseous bodies, as 
water is for solids and liquids. Hence, at 62°, air is 815 times lighter than 
water, and 11,065 times lighter than mercury. The bulk of air varies with its 
temperature and the pressure affecting it, according to the same laws as other 
gases (pages 31 and 68.)$ 

The mean pressure of the atmosphere at the surface of the sea is generally 
estimated as equal to the weight of a column of mercury of 30 inches in height, 
which is about 1 5 pounds on the square inch of surface, and is equivalent to a 
column of water of nearly 34 feet in height. The oxygen alone is equal to a 
column of 7.8 feet of water over the whole earth's surface, from which an idea 
may be formed of the immense quantity of that element, and how small the 
effect must be of the oxidating processes observed at the earth's surface in di- 
minishing it. If the atmosphere were of uniform density its height, as inferred 

* Boussaingault, Ann. de Ch. et de Ph. t. 67, p. 5, and 69, p. 353. 

t Kuhlman, Phil. Mag. 3rd Series, vol. 14, p. 157. 

t An. de Ch. et de Ph. t. 67, p. 242. 

§ The rate of the expansion of gases by heat has lately been corrected by Rudberg, who 
finds that 1 volume of gas at 32° becomes 1.365 vol. at 212°, which gives a dilatation of 
0.002028, or l-493rd part, instead of 1.480th of the bulk at 32°, for each degree Fahrenheit. 
If the expansion be expressed in parts of the bulk at 0° Fahr. which is more convenient for 
calculation, the expansion is 1-461 part for each degree. The volume of a gas at 0° being 

1, at any higher temperature it is always = 1 -\- LI — r ', 



THE ATMOSPHERE. 205 

from the barometer, would be 11,065 times 30 inches, or 5.238 miles, but the 
density of air being proportional to the pressure upon it, diminishes with its 
elevation, the superior strata being always more rare and expanded than the 
inferior strata upon which they press. 



DENSITY OF THE ATMOSPHERE. 

Height above the sea in miles. Volume. 





2.705 

5.41 

8.115 

10.82 

13.525 

16.23 



1 
2 
4 
8 
16 
32 
64 



At a height of 2.705 miles (11,556 feet) the atmosphere is of half density, by 
calculation, or 1 volume is expanded into 2, and the barometer would stand at 
15 inches; the density is again halved for every 2.7 miles additional elevation. 
From calculations founded on the phenomena of refraction, the atmosphere is 
supposed to extend, in a state of sensible density, to a height of nearly 45 miles. 
It is certainly limited, but whether by the cold prevailing in its higher regions, 
which may liquefy or even solidify the aerial particles, or from their expansibility 
having a natural limit is uncertain. The atmospheric pressure also varies at 
the same place, from the effect of winds and other causes, which are not fully 
understood. Hence, the use of the barometer as a weather glass ; for wet and 
stormy weather is generally preceded by a fall of the mercury in the barometer, 
and fair and calm weather by its rise. 

The temperature of the atmosphere is greatest at the earth's surface, and has 
been observed to diminish one degree for every 352 feet of ascent, in the lower 
strata. It is believed, however, that the progressive diminution is less rapid at 
great distances from the earth. But at a certain height, the region of perpetual 
congelation is attained even in the warmest climates; the summits of the Andes, 
which rise 21,000 feet, being perpetually covered with snow under the equator. 
The line of perpetual congelation, which has been fixed at 15,207 feet at 0° 
latitude, descends progressively in higher latitudes, being 3,818 feet at 60°, and 
only 1,016 feet at 75°. The decrease of temperature with elevation in the 
atmosphere is ascribed to two causes. 1°. To the property which air has of 
becoming cold by expansion, which arises from an increase of the latent heat 
of air, like that of steam, with rarefaction (page 60.) The actual temperature 
of the different strata of the atmosphere is indeed believed to be that due to 
their dilatation, supposing that they had all the same original temperature and 
density as the lowest stratum. 2°. To the circumstance that the atmosphere 
derives its heat principally from contact with the earth's surface. The sun's 
rays appear to suffer little absorption in passing through the atmosphere; but 
there are some observations on the force of solar radiation which are not easily 
reconciled with that circumstance. A thermometer, of which the bulb is black- 
ened, rises a certain number of degrees above the temperature of the air, when 
exposed to sun, but the rise is decidedly greater on high mountains than near 
the level of the sea, and in temperate, or even arctic climates, which is more 
remarkable, than within the tropics. It is a question how solar radiation is 
obstructed in the hotter climates. (Daniell's Meteorological Essays, 2nd ed.) 

The blue colour of the sky has been found by Brewster to be due to light 
that has suffered polarization, which is therefore reflected light, like the white 
18 



206 



NITROGEN. 



light of clouds. The air of the atmosphere must therefore have a disposition to 
absorb the red and yellow solar rays and to reflect the blue rays. At great 
heights, the blue colour of the sky was observed by Theodore de Saussure to 
become deeper and deeper, being mixed with black, owing to the absence of 
white reflecting vesicular vapour or clouds. The red and golden tints of clouds 
appear to be connected with a remarkable property of steam lately discovered 
by Professor Forbes. A light seen at night through steam issuing into the 
atmosphere from under a pressure of from 5 to 30 pounds on the inch, is found 
to appear of a deep orange red colour, exactly as if observed through a bottle 
containing nitrous acid vapour. The steam, when it possesses this colour, is 
mixed with air, and on the verge of condensation ; and it is known that the 
golden hues of sunset depend upon a large proportion of vapour in the air, and 
are indeed a popular prognostic of rain.* 

The movement of masses of air, or wind, is always produced by inequality of 
temperature of the atmosphere at different points of the earth's surface, or in 
different regions of the atmosphere of equal elevation. The primary movement 
is always an ascending current, the heated and expanded air ov§r some spot 
rising in a vertical column, Dense and colder air flows towards that point 
producing the horizontal current which is remarked by an observer on the 
earth's surface. Some winds are of a very limited range, and depend upon 
local circumstances; such are the sea and land breeze experienced upon the 
coasts of tropical countries. From its low conducting power, the surface of the 
land is more quickly heated than the sea, so that soon after sunrise the expanded 
air over the former begins to ascend, and is replaced by the colder air from the 
sea, forming the sea breeze. But after sunset, the earth's heat being less in 
quantity, is more quickly dissipated by radiation than that of the sea, and the 
air over the land becomes dense and flows outwards, displacing the air over the 
sea, and producing the land breeze. It is obvious that these inferior currents 
must be attended by a superior current in an opposite direction, or that the air 
in these winds is carried in a perpendicular vortex of no great extent, of which 
the motion is reversed twice every twenty-four hours. A grand movement of 
a similar nature is produced in the atmosphere, from the high temperature of 
the equatorial compared with the polar regions of the globe ; the air over the 
former constantly ascending, and having its place supplied by horizontal cur- 
rents from the latter, within the lower region of the atmosphere. Hence, if the 
earth were at rest, the wind would constantly blow at its surface, from the poles 
to the equator, and in the opposite direction in the upper strata of the atmos- 
phere. But the earth, accompanied by its atmosphere makes a diurnal revo- 
lution upon its axis, in which any point on its surface is always passing to a 
point in space previously to the east of it, and with a velocity proportional to its 
circle of latitude on the globe; a velocity which is consequently nothing at the 
poles, and attains its maximum at the equator. The result of this is, that the 
lower current or polar stream, in tending to the equator, is constantly passing 
over parallels of latitude which have a greater degree of velocity of rotation to 
the east* than the stream itself, which comes thus to be felt as a resistance from 
the east; and instead of appearing as a wind directly from the north as it really 
is, this stream appears as a wind from the east with a certain northerly decli- 
nation, which diminishes as the stream approaches the equator, where it flows 
directly from the east, constituting the great trade- wind which constantly blows 
across the Atlantic and Pacific Oceans from east to west within the tropics. Our 
keen east winds in spring have a low temperature which attests their arctic 
origin. The upper or equatorial current has its course deflected by similar 



* Phil. Mag . 3rd Series, vol. 14, pp. 121 and 425, and vol. 15, pp. 25, and 419. 



THE ATMOSPHERE. 207 

causes ; starting from the equator it has a greater projectile force to the east 
than the parallels of latitude over which it has to pass, and retaining this motion 
towards the east it appears, as it passes over them, a west wind or wind from 
the west. The upper current, flowing in the opposite direction from the trade- 
wind below, was actually experienced by Humboldt and Bonpland on the summit 
of the Peak of Teneriffe, and has been indicated at various times by the trans- 
port of volcanic ashes by its means. 

On the great oceans within the temperate zone, westerly winds prevail 
greatly over easterly, which are supposed by some to be the upper current 
descending to the surface of the earth. These westerly winds temper the 
climate of the western sea-board both of Europe and America, which is much 
milder than the climate of their eastern coasts. 

The nature of the movement of the atmosphere in hurricanes has lately re- 
ceived considerable elucidation. It appears that they move in circles, and are 
great horizontal vortices, which are probably produced by currents of air meet- 
ing obliquely, like the little eddies or whirlwinds formed at the corner of streets. 
The whole vortex also travels, but its movement of translation is slow compared 
with its velocity of rotation.* 

The properties of the atmosphere are much affected by the presence of watery 
vapour in it, which it acquires from contact with the surface of the sea, lakes, 
rivers and humid soil. The quantity which can rise into the air is limited by 
its temperature (page 75,) and comes to be deposited again from various causes. 
The surface of the earth is cooled by radiation, and occasions the precipitation 
of dew from the air in contact with it. Vapour is also condensed into drops, 
from various agencies within the atmosphere itself. The following are ttm 
principal causes of clouds and rain. 1°. The ascent of air in the atmosphere, 
and its consequent rarefaction, which is attended with cold. A cloud will be 
observed within the receiver of an air pump, on the plate of which a little water 
has been spilt, on making two or three rapid strokes of the pump, which is due 
to this cause. It is observed in operation in the formation of the clouds and 
mists which settle on the summits of mountains. The wind passing over the 
surface of a level country is impeded by a mountain; rising in the atmosphere 
the stream overcomes the obstacle, and produces a cloud as it passes over the 
mountain, which appears stationary on its summit. 2°. The mixing of opposite 
currents of hot and cold air, both saturated with humidity, may occasion rain, 
from the circumstance, first conjectured by Dr. Hutton, that the currents of air 
on mixing and attaining a mean temperature, are incapable of sustaining the 
mean quantity of vapour. Thus, supposing equal volumes of air at 60° and 40°, 
both saturated with vapour, to be mixed ; the tension of vapour at the former 
temperature being the 0.524th of an inch of mercury, and at the latter the 0.263rd 
of an inch, the mean tension is the 0.393rd of an inch. But the tension of vapour 
at 50°, the intermediate temperature is only the 0.375th of an inch ; and con- 
sequently the excess of the former tension, or vapour of the 0.018th of an inch 
of tension, must condense as rain. But this is an inconsiderable cause of rain 
compared with the next. 3°. Contact of air in motion with the cold surface of 
the earth, appears to be the most usual cause of its refrigeration, and of the pre- 
cipitation of rain from it. The mean temperature of January in this country is 
about 34°, but with a south west wind the thermometer may be observed 
gradually to rise in the course of 48 hours to 54°. Now supposing this wind 
to be saturated with vapour at 54° and to be cooled to 34°, as it is on its first 
arrival, the moisture which it will deposite is very considerable, as will appear by 
the following calculation. 

* See the work of Colonel Reid on the Law of Storms; and Athenaeum, August 25, lo33. 
(p. 594.) 



208 NITROGEN. 

Tension of vapour at 54° . . 0.429 inch. 
" at 34° . . 0.214 " 



Condensed . . 0.215 " 

When clouds form at temperatures below 32°, the aqueous vapour is converted 
into an infinity of little needle-like crystals, which often diverge from each other 
at angles of 60° and 120°, as do also the thin crystals in freezing water. Snow 
differs very much in the arrangement of these spiculae, but the flakes are all of 
the same configuration in the same storm. Hail is also produced by cold, but 
in circumstances which are entirely different. It occurs only in summer or in 
warm climates, and when the sun is above the horizon. It seems to be produced 
in a humid ascending current of air, greatly cooled by rarefaction, which has an 
upward velocity sufficient to sustain the falling hailstones at the same place till 
they attain considerable magnitude. The formation of hail is always attended 
with thunder or signs of electricity ; and it has been found that small districts 
may be protected from its devastations by the elevation of many thunder rods. 
Analysis of air. — A knowledge of the composition of the atmosphere followed 
that of its constituent gases. Various modes of analysis are practised : — 1°. A 
stick of phosphorus introduced into a known measure of air in a graduated tube, 
effects a complete absorption of the oxygen in 24 hours. On afterwards with- 
drawing the phosphorus the diminution of volume may be observed, which 
always indicates 20 or 21 per cent, of oxygen. 2°. A known measure of air 
may be mixed with a slight excess of hydrogen more than sufficient to combine 
with its oxygen, 100 volumes air, for example, with 50 volumes of hydrogen, 
and the mixture exploded in a strong glass tube of proper construction, by means 
of the electric spark. The diminution in volume of the gases after combustion 
is observed ; and as oxygen and hydrogen unite in the exact ratio of one volume 
of the first to two volumes of the second, one-third of the diminution represents 
the volume of oxygen in the measure of air employed. The tube used for this 
purpose is called the voltaic eudiometer. The eudiometer of Dr. Ure is an 
excellent instrument of this kind. It is formed of a straight tube moderately 
Fig 75 stout °f aDOut l-4th or 3-8ths of an inch internal diameter, 

sealed at one end, and about 22 inches long. The closed 
end of this tube being softened by heat, two stout platinum 
wires are thrust through the glass from opposite sides of 
the tube, so that their extremities in the tube approach 
within one tenth of an inch of each other. These are in- 
tended for the transmission of the electric spark, and are 
retained, as if cemented, in the apertures of the glass when 
the latter cools. One half the tube next the closed end is 
afterwards graduated into hundredths of a cubic inch, and 
the tube is bent in the middle, like a syphon, as represented 
by a. in the figure. By a little dexterity, a portion of the 
gaseous mixture to be exploded is transferred to the sealed 
limb of the instrument, at the water or mercurial trough, 
and the measure noted with the liquid at the same height in both limbs. The 
mouth of the open limb may then be closed by a cork, which can be fixed down 
by soft copper wire. A chain being now hung to the one platinum wire, the 
other is presented to the prime conductor of an electric machine, or to the knob 
of a charged Leyden phial b, so as to take a spark through the mixture, which 
is thereby exploded. The risk of the tube being broken by the explosion, which 
is very considerable in the ordinary form of the eudiometer, is completely 
avoided in this instrument by the compression of the air retained by the cork in 
the open limb, this air acting as a recoil spring upon the occurrence of the ex- 




THE ATMOSPHERE. 209 

plosion in the other limb. 3°. The combustion of the mixed gases may be de- 
termined without explosion by means of a little pellet of spongy platinum, and 
the experiment can then be conducted over mercury in an ordinary graduated 
tube. 4°. Another exact method of removing oxygen from air, recommended 
by Gay-Lussac, is the introduction into the air of slips of copper moistened with 
hydrochloric acid, which absorb oxygen with great avidity. 5°. Lastly, a 
method lately practised by Saussnre; in which the air is deprived of its oxygen 
by agitating it with a small quantity of water and metallic lead in thin turnings, 
which becomes white hydrated oxide of lead. All these methods give accurate 
results when conducted with proper precautions. The conclusion which they 
have led to is, that the proportion of oxygen in 100 volumes of dry and pure 
air is not subject to variation, and lies between 20.8 and 21 volumes.* It is 
generally assumed as 21 volumes, which gives the proportions — 

ATMOSPHERIC AIR BY WEIGHT. 

Oxygen 23.1 

Nitrogen 76.9 



100.0 



Besides these constituents, the atmosphere always contains a variable quantity 
of watery vapour and carbonic acid gas. The presence of the latter is observed 
by exposing to the air a basin of lime-water, which is soon covered by a pellicle 
of carbonate of lime. Its proportion is generally ascertained by adding barytes- 
water of a known strength, from a graduated pipette, to a large bottle of the air 
to be examined; agitating after each addition, till a slip of yellow turmeric paper 
is made permanently brown by the barytes-water after agitation, which proves 
that more of the latter has been added than is neutralized by the carbonic acid 
of the air. The carbonic acid is in the equivalent proportion (by weight) of the 
quantity of barytes which has been neutralized. Like every subject connected 
with the atmosphere, the proportion of carbonic acid which it contains has been 
ably investigated by the Saussures. The elder philosopher of that name detected 
the presence of this gas in the atmosphere resting upon the perpetual snows of 
the summit of Mount Blanc, so that there can be no doubt that carbonic acid is 
diffused through the whole mass of the atmosphere. The younger Saussure has 
ascertained, by a series of several hundred analyses of air that the mean pro- 
portion of carbonic acid is 4.9 volumes in 10,000 volumes of air, or almost ex- 
actly 1 in 2000 volumes : but it varies from 6.2 as a maximum to 3.7, as a 
minimum in 10,000 volumes. Its proportion near the surface of the earth is 
greater in summer than in winter, and during night than during day upon an 
average, of many observations. It is also rather more abundant in elevated 
situations, as on the summits of high mountains, than in the plains; a distribution 
of this gas which proves that the action of vegetation at the surface of the earth 
is sufficient to keep dowm the proportion of it in the atmosphere, within a certain 
limit, f An enormous quantity of carbonic acid is discharged from the elevated 
cones of the active volcanoes of America, according to the observations of Bous- 
singault, which may partly account for the high proportion of that gas in the 
upper regions of the atmosphere. The gas emitted from the volcanoes of the 
old world, according to Davy and others, is principally nitrogen. 

Carbonic acid is a constituent of the atmosphere which is essential to vege- 
table life, plants absorbing that gas, and all of them deriving from it a part, and 

* Saussure, An. de Ch. ct de Ph. t. 62, p. 219. 

t Saussure, An. de Ch. et de Ph. t. 38, p. 411, and t. 44, p. 5. 

18* 



210 NITROGEN. 

some of them the whole of their carbon. Extensive forests, such as those of the 
Landes in France, which grow upon sands absolutely destitute of carbonaceous 
matter, derive their carbon entirely from this source. But the oxygen of the 
carbonic acid is not retained by the plant, for the lignin and other constituent 
principles of vegetables, contain, it is well known, no more oxygen than is 
sufficient to form water with their hydrogen, and which indeed has entered the 
plant as water. The oxygen of the carbonic acid must therefore be returned 
in some form to the atmosphere. The discharge of pure oxygen gas from the 
leaves of plants was first observed by Priestley, and the general action of plants 
upon the atmosphere has subsequently been minutely studied by Sir H. Davy 
and Dr. Daubeny. It appears that plants have a double action upon the 
atmosphere; they withdraw carbonic acid from it, appropriating the carbonaceous 
part of that gas to their own wants and evolving its oxygen; and they also 
absorb oxygen from the atmosphere and return carbonic acid in its place, an 
action corresponding with the respiration of animals. Of these actions the latter 
predominates during the night, and the former during the day, but the result of 
both is that plants during twenty-four hours yield considerably more oxygen 
than they consume. That they fully compensate for the loss of oxygen occa- 
sioned by the respiration of animals and other natural processes is not improba- 
ble. But the mass of the atmosphere is so vast that any change in its composi- 
tion must be very slowly effected. It has indeed been estimated that the pro- 
portion of oxygen consumed by animated beings in a century does not exceed 
1 -7200th of the whole quantity. 

Other gases and vaporous bodies are observed to enter the atmosphere, but 
none of them can afterwards be detected in it, with the exception perhaps of 
hydrogen in some form, probably as the light carburetted hydrogen of marshes, 
of which Boussingault believes that he has been able to detect the presence of 
an appreciable but exceedingly minute trace.* He observed concentrated sul- 
phuric acid to be blackened when exposed in a glass capsule to the air, pro- 
tected from dust, and at a distance from vegetation, which he ascribes to the 
occasional presence in the air of some volatile carbonaceous compound, which 
is absorbed and decomposed by the acid. Of the odoriferous principles of plants, 
the miasmata of marshes and other matters of contagion, the presence, although 
sufficiently obvious to the sense of smell, or by their effects upon the human 
constitution, cannot be detected by chemical tests. But it may be remarked in 
regard to them, that few or none of the compound volatile bodies we perceive 
entering the atmosphere, could long escape destruction from oxidation. The 
atmosphere contains indeed within itself the means of its own purification, and 
slowly but certainly converts all organic substances exposed to it into simpler 
forms of matter, such as water, carbonic acid, nitric acid and ammonia. Al- 
though the occasional presence of matters of contagion in the atmosphere is 
not to be disputed, still it is an assumption without evidence, that these sub- 
stances are volatile or truly vaporous. Other matters of infection with which 
we can compare them, such as the matter of cow-pox, may be dried in the air, 
and are not in the least degree volatile. Indeed volatility of a body implies a 
certain simplicity of constitution and limit to the number of atoms in its inte- 
grant particle, which true organic bodies appear not to possess. It is more 
probable that matters of contagion are highly organized particles of fixed mat- 
ter, which may find its way into the atmosphere, notwithstanding, like the pol- 
len of flowers, and remain for a time suspended in it ; a condition which is 
consistent with the admitted difficulty of reaching and destroying those bodies 
by gaseous chlorine, and with the washing of walls and floors as an ordinary 



* An. deCh. et Ph. t. 57, p. 148. 



NITROUS OXIDE. 211 

disinfecting practice. On this obscure subject I may refer to a valuable paper 
by the late Dr. Henry upon the application of heat to disinfection, in which it is 
proved that a temperature of 212° is destructive to such contagious matters as 
could be made the subject of experiment.* 

The compounds of nitrogen with oxygen are the following : — 

Nitrous oxide or protoxide of nitrogen NO 

Nitric oxide or deutoxide of nitrogen N0 2 

Nitrous acid (hyponitrous acid of Turner) N0 3 

Peroxide of nitrogen (nitrous acid of Turner, hyponitric acid of Thenard) N0 4 
Nitric acid N0 5 



NITROUS OXIDE. 
Syn, protoxide of azote. Eq. Til or 22.2; NO; density 1527.3; 



This gas was discovered by Dr. Priestley about 1776, and studied by Davy, 
whose " Researches, Chemical and Philosophical," published in 1809, con- 
tain an elaborate investigation of its properties and composition. Davy first 
observed the stimulating power of nitrous oxide when taken into the lungs, a 
property which has since attracted a considerable degree of popular attention 
to this gas. 

Preparation. — Nitrous oxide is always prepared from the nitrate of ammo- 
nia. Some attention must be paid to the purity of that salt, which should con- 
tain no hydrochlorate of ammonia. It is formed by adding pounded carbonate 
of ammonia to pure nitric acid, which, if concentrated, may be previously 
diluted with half its bulk of water, so long as there is effervescence; and a 
small excess of the carbonate may be left at the end in the liquor. The so- 
lution is concentrated till its boiling point begins to rise above 250°, and a 
drop of it becomes solid on a cool glass plate. On cooling, it forms a solid 
cake, which may be broken into fragments. To obtain nitrous oxide, a 
quantity of this salt, which should never be less than 6 or 8 ounces, is intro. 
duced into a retort, or a globular flask, P «g 

called a bolt-head a, and heated by a 
charcoal chauffer ft, the diffused heat of 
which is more suitable than the heat 
of a lamp. Paper may be pasted over 
the cork of the bolt-head to keep it air- 
tight. At a temperature not under 
340° the salt boils and begins to un- 
dergo decomposition, being resolved 
into nitrous oxide and water. As heat 
is evolved in this decomposition, which 
is a kind of combustion or deflagra- 
tion, the chuafTer must be withdrawn to 
such a distance from the flask, as to 
sustain only a moderate ebullition. If 
the temperature is allowed to rise too high, the ebullition becomes tumultuous, 
and the flask is filled with white fumes, which have an irritating odour; and 
the gas which then comes off is little more than nitrogen. Nitrous oxide 
should be collected in a gasometer or in a gas-holder filled with water of a 
temperature about 90°, as cold water absorbs much of this gas. The whole 

* Phil. Mag. 2nd Series, v. 10, p. 363, and vol. 11, pp. 22, 207, (1832.) 





212 NITROGEN. 

salt undergoes the same decomposition, and nothing whatever is left in the 
retort.* 

Nitrous oxide is likewise produced when the salt called nitrosulphate of am- 
monia is thrown into an acid; and also when zinc and tin are dissolved in di- 
lute nitric acid, but the latter processes do not afford the gas in a state of 
purity. 

The nature of the decomposition of the nitrate of ammonia will be best ex- 
plained by the following diagram, in which an equivalent of the salt, or 1004 
parts, is supposed to be used. It will be observed that the three equivalents 
of hydrogen in the ammonia are burned, or combine with three equivalents of 
the oxygen of the nitric acid, and form water, while the two equivalents of 
nitrogen in the ammonia and nitric acid combine with the two remaining equi- 
valents of the oxygen of the latter: — 

Before decomposition. After decomposition. 

( Oxygen 100 "-'277 nitrous oxide. 

| Oxygen 100 ™-^;;;-277 nitrous oxide. 

| j Oxygen 100 

I 677 Nitric acid, i Oxvgen 100 

I I Oxygen 100 

1004 nitrate of ammonia, j [Nitrogen 177 

f Nitrogen 377 

' Hydrogen 12 5 x vV^ 112.5 water. 

j 214 5 Ammonia. < Hvdrogen 12.5 ~N^ U2.5 water. 

(.Hydrogen 12.5 -^ 112.5 water. 

[112.5 Water Water 112 5 112.5 water. 

1004 1004 1004 1004 

Or in symbols: — 

NH 3 , HO + N0 5 =2NO and 4HO. 

From the diagram it appears that 1004 £rs. of the salt yield 554 grains of 
nitrous oxide and 450 grains of water. One grain of salt yields rather more 
than one cubic inch of gas. 

Properties. — Nitrous oxide possesses the usual mechanical properties of 
gases, and has a faint agreeable smell. It has been liquefied by evolving it 
from the decomposition of the nitrate of ammonia in a sealed tube, and pos- 
sessed in the liquid state an elastic force of above 50 atmospheres at 45°. The 
gas is formed by the union of a combining measure^or 2 volumes of nitrogen, 
with a combining measure, or 1 volume of oxygen, which are condensed into 
2 volumes, the combining measure of this gas. The weight of a single volume, 
or the density of the gas, is therefore 

976+976+1102.6 ^ 1527 3 

Cold water agitated with this gas dissolves about three-fourtTis of its volume 
of the gas, and acquires a sweetish taste, but, I believe, no stimulating pro- 
perties. Bodies which burn in air, burn with increased brilliancy in this gas, 
if introduced in a state of ignition. A newly blown out taper with a red wick 
may be rekindled in it, as in oxygen. Mixed with an equal bulk of hydrogen 
and ignited by flame and the electric spark, it detonates violently. In all these 
cases of combustion, the nitrous oxide is decomposed, its oxygen uniting with 
the combustible and its nitrogen being set free. When transmitted through a 
red-hot porcelain tube, nitrous oxide is likewise decomposed and resolved into 
oxygen, nitrogen, and the peroxide of nitrogen. 

Nitrous oxide was supposed by Davy to combine with alkalies, when gene- 
rated in contact with them, but these compounds have since been found to 
contain nitrosulphuric acid. 

* For the preparation and properties of this and other gases, the Elements of Chemistry 
(1829) of the late Dr. Henry may be consulted with advantage. 



NITRIC OXIDE, 



213 



This gas may be respired for two or three minutes without inconvenience, 
and when the gas is unmixed with air, and the lungs have been well emptied 
of air before respiring, it induces an agreeable state of revery or intoxication, 
often accompanied with considerable excitement, which lasts for a minute or 
two, and disappears without any unpleasant consequences. The gas from an 
ounce and a-half or two ounces of nitrate of ammonia is sufficient for a dose, 
and it should be respired from a bag of the size of a large ox-bladder, and pro- 
vided with a wooden tube of an inch internal diameter. The volume of the 
gas diminishes rapidly during the inspiration, and finally only a few cubic 
inches remain. An animal entirely confined in this gas soon dies from the 
prolonged effects of the intoxication. 



NITRIC OXIDE. 



Syn. DEUTOXIDE OF AZOTE, DEUTOXIDE OF NITROGEN, BINOXIDE OF NITROGEN 

(Turner,) nitrous gas (Priestley.) Eq. 377 or 30.2; N0 2 ; density 1039.3; 



This gas which comes off during the action of nitric acid upon most metals, 
appears to have been collected by Dr. Hales, the father of pneumatic chemis- 
try, but its properties were first minutely studied by Dr. Priestley. 

Preparation. — Nitric oxide is easily procured by the action of nitric acid 
diluted to the specific gravity 1.2, upon sheet copper clipped into small pieces. 
As no heat is required, this gas may be evolved like hydrogen from a gas bot- 
tle (page 195.) Mercury may be substituted for copper, but it is then neces- 
sary to apply a gentle heat to the materials. This gas may be collected and 
retained over water without loss. 

In dissolving in nitric acid, the copper takes oxygen from one portion of 
acid and becomes oxide of copper, which combines with another portion of 
acid, and forms the nitrate of copper, the solution of which is of a blue colour. 
The portion of nitric acid which is decomposed, losing three equivalents of 
oxygen and retaining two, appears as nitric oxide gas. This is more clearly 
shown in the following diagram: — 



ACTION OF NITRIC ACID UPON COPPER. 



Before decomposition. 





^Nitrogen . 


177 




Oxygen . 


100 


677 Nitric acid < 


Oxygen . 


100 




Oxygen . 


100 




Oxygen . 


100 




..Oxygen • 


100 


396 Copper . 


Copper 


396 


677 Nitric acid 


•Nitric acid 


677 


396 Copper . 


Copper 


396 


677 Nitric acid 


Nitric acid 


677 


396 Copper . 


Copper 


396 


677 Nitric acid 


Nitric acid 


677 




After decomposition. 
377 Nitric oxide. 



3896 



3396 



1173 Nitrate of copper. 
1173 Nitrate of copper. 
1173 Nitrate of copper. 
3896 



214 NITROGEN. 

Or in symbols : — 

4NO, and 3Cu = 3(Cu O, N0 5 ) and N0 2 . 

Properties. — This gas is colourless, but when mixed with air it produces 
ruddy fumes of the peroxide of nitrogen. It is irritating, and causes the glottis 
to contract spasmodically when an attempt is made to respire it. Nitric oxide 
has never been liquefied : water at 60° according to Dr. Henry, takes up only 
5 or 6 per cent, of this gas. It is formed of one combining measure of nitro- 
gen or 2 volumes, and two combining measures of oxygen or 2 volumes, united 
without condensation, so that the combining measure of nitric oxide contains 4 
volumes. The weight of one volume, or the density of the gas, is therefore 

976+976+1402.6+1102.6 __ ^ g 

This gas is not decomposed by a low red heat. 

Many combustibles do not burn in nitric oxide, although it contains half its 
volume of oxygen. A lighted candle and burning sulphur are extinguished by 
it ; mixed with hydrogen, it is not exploded by the electric spark or by flame, 
but it imparts a green colour to the flame of hydrogen burning in air. Phos- 
phorus and charcoal, however, introduced in a state of ignition into this gas, 
continue to bum with increased vehemence. The state of combination of the 
oxygen in this gas appears to prevent that substance from uniting with com- 
bustibles, unless, like the last two mentioned, they evolve so much heat as to 
decompose the nitric oxide. Several of the more oxidable metals, such as iron, 
withdraw the half of the oxygen from this gas, when left in contact with it, and 
convert it into nitrous oxide. 

• No property of nitric oxide is more remarkable than its attraction for oxygen, 
and it may be employed to separate this from all other gases. Nitric oxide in- 
dicates the presence of free oxygen in a gaseous mixture, by the appearance of 
fumes which are pale and yellow, with a small, and reddish brown and dense 
with a large proportion of the latter gas ; and also by a subsequent contraction 
of the gaseous volume, arising from the absorption of these fumes by water. 
Added in sufficient quantity, nitric oxide will thus withdraw oxygen most com- 
pletely from any mixture. But notwithstanding this property, nitric oxide can- 
not be employed with advantage in the analysis of air or similar mixtures, for 
the contraction which it occasions does not afford certain data for determining 
the proportion of oxygen which has disappeared. Nitric oxide is capable of 
combining with different proportions of oxygen, a combining measure or 4 
volumes of the gas uniting, in such experiments, with 1,2 or 3 volumes of 
oxygen, and forming nitrous acid, peroxide of nitrogen or nitric acid, or several 
of these compounds at the same time. 

This oxide of nitrogen, like the preceding, is a neutral body, and has a very 
limited range of affinity. A substance is left on igniting the nitrate of potash 
or barytes, which was supposed to be a compound of nitric oxide with potas- 
sium, or barium, but Mitscherlich finds it to be either the caustic protoxide itself 
or the peroxide of the metal. But nitric oxide is absorbed by a solution of the 
sulphate of iron, which it causes to become black ; the greater part of the gas 
may be expelled again by boiling the solution. All the soluble protosalts of 
iron have the same property, and the nitric oxide remains attached to the oxide 
of iron when precipitated in the insoluble salts of that metal. The proportion 
of nitric oxide in these combinations is found by Peligot to be definite; one eq. 
of the nitric oxide to four of the protoxide of iron ; or, the nitric oxide contains 
the proportion of oxygen required to convert the protoxide into peroxide of 
iron.* Nitric oxide is also absorbed by nitric acid. With sulphurous acid 

* An. de Ch. et de Ph. t. 54, p. 17, 



NITROUS ACID. 215 

nitric oxide forms a compound which will be more particularly noticed under 
that acid. 

NITROUS ACID. 

Syn. azotous acid (Thenard,) hyponitrous acid (Turner.) Eq. 477 or 
38.2; N0 3 . 

The direct mode of forming this compound is by mixing 4 volumes of nitric 
oxide with 1 volume of oxygen, both perfectly dry, and exposing the mixture 
to a great degree of cold. The gases unite and condense into a liquid of a 
green colour, which is very volatile, and forms a deep reddish yellow coloured 
vapour. Nitrous acid prepared in this way is decomposed at once when thrown 
into water ; an effervescence occurring from the escape of nitric oxide, and 
nitric acid being produced which gives stability to a portion of the nitrous acid. 
Nitrous acid cannot be made to unite directly with alkalies and earths, proba- 
bly owing to the action of water first described. But when oxygen gas is 
mixed with a large excess of nitric oxide, in contact with a solution of caustic 
potash, the gases were found by Gay-Lussac always to disappear in the propor- 
tions of nitrous acid, which was produced and entered into combination with 
the potash, forming a nitrite of potash. Similar nitrites may also be produced 
by calcining the nitrate of potash till the fused salt becomes alkaline ; or by boil- 
ing the nitrate of lead with metallic lead. The nitrite of potash may be dis- 
solved and filtered, and the solution precipitated by nitrate of silver; a process 
which gives the nitrite of silver, a salt possessing a sparing degree of solubility 
like that of cream of tartar, but which may be purified by solution and crystal- 
lization, and then affords a ready means of obtaining the other nitrites by double 
decomposition (Mitscherlich.) When free sulphuric acid is added to a solution 
of nitrite of silver, the liberated nitrous acid is immediately resolved into nitric 
acid and nitric oxide. The subnitrite of lead, on the other hand, may be decom- 
posed by the bisulphate of potash or soda to obtain a neutral nitrite of one of 
these bases (Berzelius.) 

Nitrous acid is also capable of combining with several acids, in particular with 
iodic, nitric, and sulphuric acids. Its combination with the last is a crystalline 
solid of specific gravity 1.831, which is of considerable interest from its oc- 
currence in the manufacture of sulphuric acid. According to the analysis 
of Gaultier de Claubry, its constituents are 5 eq. of sulphuric acid, 2 of ni- 
trous acid and 4 of water. When moist sulphurous acid gas and peroxide of 
nitrogen are in contact, this crystalline compound is formed, the sulphurous 
acid gaining the oxygen which the other loses. A little nitrogen appears at 
the same time, so that a portion of the peroxide of nitrogen must be com- 
pletely decomposed. If the crystalline compound comes in contact with 
steam or a small quantity of water, the sulphuric acid combines exclusively 
with the water, and the liberated nitrous acid is resolved into nitric oxide and 
peroxide of nitrogen, both of which escape as gas. But with a large quantity 
of water a portion of the nitrous acid is always decomposed into nitric oxide 
gas and nitre acid.* 

It must be admitted that some obscurity still hangs over the nature of this 
acid, when uncombined, the formation of the nitrites by Gay-Lussac's process 
appearing to be incompatible with the properties ascribed to the free acid by 
TJulong. Its tendency to combine with acids has already been noticed as as- 
similating this compound of nitrogen to arsenious acid and the oxide of anti- 
mony (page 121.) 

* An. de Ch. et de Ph. t. 45, p. 284. 



216 NITROGEN. 

PEROXIDE OF NITROGEN. 

Syn, nitrous acid (Turner,) hyponitric acid, nitrous gas {Berzelius.) 
JEq. 577 or 46.2; N0 4 ; density 3181.2; 

This compound forms the principal part of the ruddy fumes which always 
appear on mixing nitric oxide with air. As it cannot be made to unite either 
directly or indirectly with bases, and has no acid properties, any designation 
for this oxide of nitrogen which implies acidity should be avoided, and the 
name nitrous acid in particular, which is applied on the continent to the pre- 
ceding compound. The name peroxide of nitrogen is more in accordance 
with the rules generally followed in naming such compounds. 

Preparation. — When 4 volumes of nitric oxide and 2 of oxygen, both per- 
fectly dry, are mixed, this compound is alone produced, and the 6 volumes of 
mixed gases are condensed into 2 volumes, which may be considered the com- 
bining measure of peroxide of nitrogen. The weight of 1 volume, or the 
density of this gas must therefore be 

1039.3x4+1102.6x2 ^ 3181 2 

The peroxide of nitrogen is also contained in the coloured and fuming nitric 
acid of commerce, and may be obtained in the liquid condition, by gently 
warming that acid, and condensing the vapour which comes over, by trans- 
mitting it through a glass tube surrounded by ice and salt. But it is prepared 
with most advantage from the nitrate of lead, the crystals of which, after being 
pounded and dried, are distilled in a retort of stoneware or hard glass, at a red 
heat, and the red vapours condensed in a receiver kept very cold by a freezing 
mixture. Oxygen gas escapes during the whole process, the nitric acid of the 
nitrate of lead being resolved into oxygen and peroxide of nitrogen; or N0 5 
= N0 4 and O. As obtained by the last process, which was proposed by Du- 
long, peroxide of nitrogen is a highly volatile liquid, boiling at 82°, of a red 
colour at the usual temperature, orange yellow at a lower temperature, and 
nearly colourless below zero, of density 1.451, and a white solid mass at — 40°. 
It is exceedingly corrosive, and like nitric acid stains the skin yellow. The 
red colour of its vapour becomes paler at a low temperature; but with heat in- 
creases greatly in intensity, so as to appear quite opaque when in a considera- 
ble body at a high temperature. It is the vapour which Brewster observed to 
produce so many dark lines in the spectrum of a ray of light which had passed 
through it (page 84.) The peroxide is not decomposed by a low red heat, 
and appears to be the most stable of the oxides of nitrogen. No compound 
of it is known, unless peroxide of nitrogen be the radical, as some suppose, 
of nitric acid. But Berzelius is inclined to consider this oxide as itself a com- 
pound of nitric and nitrous acids, for N0 5 -fNO,=2N0 4 .* 

The liquid peroxide of nitrogen is partially decomposed by water, nitric 
oxide coming off with effervescence, and more and more nitric acid being pro- 
duced, in proportion to the quantity of water added; but a portion of the per- 
oxide always escapes this action, being protected by the nitric acid formed. 
In the progress of this dilution the liquid undergoes several changes of colour 
passing from red to yellow, from that to green, then to blue, and becoming at 
last colourless. The peroxide of nitrogen is readily decomposed by the more 
oxidable metals, and is a powerful oxidizing agent. 

* Traite de Chimie, par J. J. Berzelius, traduit par B. Valerius, Bruxelles, 1838, t. 1, p. 
195. An excellent edition of the most valuable system of chemistry which we at present 



NITRIC ACID. 217 



NITRIC ACID. 

Syn. azotic acid (Thenard.) Eq. 677; N0 5 ; does not exist except in com- 
bination. 

A knowledge of this highly important acid has descended from the earliest 
ages of chemistry, but its composition was first ascertained by Cavendish, in 
1785. He succeeded in forming nitric acid from its elements, by transmitting 
a succession of electric sparks during several days, through a small quantity of 
air, or through a mixture of 1 volume of nitrogen and 2^ volumes of oxygen, 
conlined in a small tube over water, or over solution of potash; in the last case 
the absorption of the gases was complete and nitrate of potash was obtained. 
A trace of this acid in combination with ammonia has been detected in the rain 
of thunder storms, produced probably in the same manner. It was also ob- 
served by Guy-Lussac to be the sole product when nitric oxide is added, in a 
gradual manner to oxygen in excess over water; the gases then unite and dis- 
appear in the proportion of 4 volumes of the former to 3 of the latter. It is 
also a constituent of the salt, nitre or saltpetre, found in the soil of India and 
Spain, which is a nitrate of potash, and also of nitrate of soda which occurs 
in large quantities in South America. 

Preparation. — This acid cannot exist in an insulated state, but is always in 
combination with water, as in aqua fortis or the hydrate of nitric acid, or 
with a fixed base, as in the ordinary nitrates. The hydrate, (which is popu- 
larly termed nitric acid,) is eliminated from nitrate of potash by means of oil 
of vitriol, which is itself a hydrate of sulphuric acid. That acid unites with 
potash, in this decomposition, and forms sulphate of potash, displacing nitric 
acid, which last brings off in combination with itself the water of the oil of vi- 
triol. There is a great advantage, first pointed out by Mr. Phillips, in using 
two equivalents of oil of vitriol to one of nitrate of potash, which is 97 
of the former to 100 of the latter, or nearly equal weights. The acid and 
salt, in these proportions, are introduced into a capacious plain retort, provided 
with a flask as a receiver. Upon the application of heat, a little of the nitric 
acid firstevolved undergoes decomposition, and red fumes appear, but soon the 
vapours become nearly colourless, and are easily condensed in the receiver. 
During the whole distillation, the temperature need not exceed 260°. The 
mass remains pasty till all the nitric acid is disengaged, and then enters into 
fusion; red vapours again appearing towards the end of the process. If the 
neck of the retort now be heated, the residuary salt, while still fluid, may be 
poured out into a basin; it is the bisulphate of potash, which may be used for 
different purposes after it has solidified. The rationale of this important pro- 
cess is exhibited in the following diagram: — 

PROCESS FOR NITRIC ACID. 

Before decomposition. After dpeomDosition. 

( Nitric acid 677 ,- 789.5 Nitric acid and water. 

1267 Nitrate of potash. < 

( Potash 




C Water 

( Sulphuric acid 501 * I091 Sulphate of potash > hisul of 



613.5 Oil of Vitriol. 

6135 Oil of vitriol. Oil of vitriol 613.5 (313.5 Sulphate of water- i potash 

2494 2494 



In this operation twice as much sulphuric acid is employed, as is required to 
neutralize the potash of the nitre, by which means the whole nitric acid is 
19 



218 NITROGEN. 

eliminated without loss at a moderate temperature, and a residuary salt is left 
which is easily removed from the retort. 

With half the preceding quantity, or a single equivalent of oil of vitriol, the 
materials in the retort are apt to undergo a vesicular swelling, upon the appli- 
cation of heat, and to pass into the receiver. Abundance of ruddy fumes are 
also evolved, that are not easily condensed, and prove that the nitric acid is 
decomposed. The temperature in this process must also be raised inconve- 
niently high towards the end of the operation, in order to decompose the whole 
nitre. The peculiarities of the decomposition here arise from the formation 
of bisulphate of potash in the operation, the whole sulphuric acid uniting in 
the first instance with half the potash of the nitre. Now, it is only at an ele- 
vated temperature that the acid salt thus formed can decompose the remaining 
nitre; a temperature which is sufficient to decompose nitric acid, as may be 
proved by transmitting the vapour of the concentrated acid through a tube 
heated to the same degree. 

Properties. — 'The acid prepared by the first process is colourless or has 
only a straw yellow tint. If the oil of vitriol has been in its most concentrated 
condition, which is seldom the case, the nitric acid is in its state of highest 
concentration also, and contains no more than a single equivalent of water, 
according to Mitscherlich. The density of this acid is 1.522 at 58°; but a 
slight heat disengages a little peroxide of nitrogen from it, and its density be- 
comes 1.521. It boils at 187°, but when distilled, it is partially decomposed 
by the heat and affords a product of a strong yellow colour. Its vapour trans- 
mitted through a porcelain tube, heated to dull redness, is decomposed in a 
great measure into oxygen and peroxide of nitrogen; and into oxygen and nitro- 
gen gases, when the tube is heated to whiteness. The colourless liquid acid 
becomes yellow, when exposed to the rays of the sun, and on loosening the 
stopper of the bottle, it is sometimes projected with force, from the state of 
compression of the disengaged oxygen. Hence to preserve this acid colourless 
it must be kept in a covered bottle. It congeals at about — 40°, but diluted 
with half its weight of water, it becomes solid at 1|°, and with a little more 
water its freezing point is again lowered to —45°. Exposed to the air the 
concentrated acid fumes, from the condensation by its vapour of the moisture 
in the atmosphere. It also attracts moisture from damp air, and increases in 
weight; and when suddenly mixed with 3-4ths of its weight of water, may rise 
in temperature from 60° to 140°. 

Nitric acid has a great affinity for water, and diminishes in density with the 
proportion of water added to it, A table has been constructed by Dr. Ure, in 
which the per centage of absolute acid is expressed in mixtures of various 
densities, which is useful for reference and will be given in an appendix. 
There are several definite hydrates of this acid. The most concentrated acid 
contains a single equivalent of water; a second acid appears to exist, having 
a density of about 1 .48, which contains two of water, and forms the nitric 
acid which has little or no action upon tin, iron and some other metals; there 
is still a third acid of density 1.42, which contains four equivalents of water. 
This last hydrate was found by Dr. Dalton to have the highest boiling point 
of any hydrate of nitric acid, namely 248°, and both weaker and stronger 
acids are brought to this strength by continued ebullition, the former losing 
water and the latter acid. The density of the vapour of this hydrate is found 
to be 1243 by A. Bineau, and it contains 2 volumes of nitrogen, 5 volumes of 
oxygen and 8 volumes of steam condensed into 10 volumes, which are there- 
fore the combining measure of this vapour.* 

Nitric acid is exceedingly corrosive, and one of the strongest acids, yield- 

* An. de Ch. et de Ph. t. 68, p. 418. 



NITRIC ACID. 219 

ing only in that respect to sulphuric acid. The facility with which it parts 
with its oxygen, renders it very proper for oxidating bodies in the humid way, 
a purpose for which it is constantly employed. Nearly all the metals are ox- 
idized by means of it; some of them with extreme violence, such as copper, 
mercury and zinc, when the concentrated acid is used; and tin and iron by the 
acid very slightly diluted. Poured upon red hot charcoal, it causes a brilliant 
combustion. When mixed with a fourth of its bulk of sulphuric acid, and 
thrown upon a few drops of oil of turpentine, it occasions an explosive com- 
bustion of the oil. Sulphur digested in nitric acid at the boiling point is raised 
to its highest degree of oxidation and becomes sulphuric acid; iodine is also con- 
verted by it into iodic acid. Most vegetable and animal substances are con- 
verted by dilute nitric acid into oxalic, malic and carbonic acids. It stains the 
cuticle and nails of a yellow colour, and has the same effect upon wool; the 
orange patterns upon woollen table covers are produced by means of it. In 
the undiluted state it forms a powerful cautery. 

In acting upon the less oxidable metals, such as copper and mercury, nitric 
acid is itself decomposed, and nitric oxide gas produced, which comes off with 
effervescence. Palladium and silver when they are dissolved by the acid in 
the cold, produce nitrous acid in the liquor and evolve no gas, but this is very 
unusual in the solution of metals by nitric acid. Those metals, such as zinc, 
which are dissolved in diluted acids with the evolution of hydrogen, act in 
two ways upon nitric acid; sometimes they decompose it, so as to disengage 
a mixture of peroxide of nitrogen and nitric oxide, and at other times they de- 
compose both water and nitric acid at once, in such proportions that the hy- 
drogen of the water combines with the nitrogen of the acid to form ammonia, 
w«hich last combines with another portion of acid, and is retained in the liquor 
as nitrate of ammonia. The protoxide of nitrogen is also evolved when zinc 
is dissolved in very feeble nitric acid, which may arise from the action of hy- 
drogen upon nitric oxide. Nitric acid, in its highest state of concentration, 
exerts no violent action upon certain organic substances, such as lignin or 
woody fibre and starch, for a short time, but unites with them and forms sin- 
gular compounds. A proper acid for such experiments is procured with most 
certainty by distilling 100 parts of nitre, with no more than 60 parts of the 
strongest oil of vitriol. If paper is soaked for one minute in such an acid, and 
afterwards washed with water, it is found to shrivel up a little and become 
nearly as tough as parchment, and when dried to be remarkably inflammable, 
catching fire at so low a temperature as 356°, and burning without any nitrous 
odour. (Pelouze.) 

Nitric acid forms an important class of salts, the nitrates, which occasion 
deflagration when fused with a combustible at a hiorh temperature, from the 
oxygen in their acid, and are remarkable as a class for their general solubility, 
no nitrate being insoluble in water. The nitrate of the black oxide of mer- 
cury is perhaps the least soluble of these salts. In neutral nitrates the oxygen 
in the acid is always five times that in the base. The nitrates of potash, soda, 
ammonia, barytes and strontian, are anhydrous; but the nitrates of the exten- 
sive magnesian class of oxides all contain water in a state of intimate combi- 
nation, one equivalent at least of it appearing to be inseparable from the salt, 
and they have a formula analogous to that of hydrated nitric acid, or the nitrate 
of water itself. The nitric acid of sp. gr. 1.42 appears to be the proper 
nitrate of water, and of the four atoms of water which it contains, one is com- 
bined with the acid as base, and may be named basic water, while the other 
three are in combination with the nitrate of water, and may be termed the 
constitutional water of that salt. The same three atoms of constitutional 
water are found in all the magnesian nitrates, with the addition often of ano- 
ther three atoms of water, as appears from the following formulae:— ■> 



220 NITROGEN. 

Nitric acid, 1.42. . . .HO, N0 5 +3HO 

Prismatic nitrate of copper. . CuO, N0 5 -f3HO 

Rhomboidal nitrate of copper. . CuO, N0 5 -f3HO-|-3HO 

Nitrate of magnesia. . . . MgO, N0 5 -f 3HO+3HO 

The proportion of water in the nitrate of magnesia may be reduced, by heat- 
ing the salt, to one atom, leaving the compound MgO,N0 5 -fHO; but on 
urging the temperature still higher, the last atom of water and the acid are 
expelled together, and magnesia is left behind, neither this nor any other 
nitrate of the magnesian class being capable of existing without an atom of 
water. The nitrates of the potash and magnesian classes do not combine to- 
gether, and no double nitrates are known, nor nitrates with excess of acid. 
The nitrates with excess of metallic oxide, which are called subnitrates, ap- 
pear to be formed on the type of the magnesian class: the subnitrate of cop- 
per, being HO, N0 5 -f-3CuO, or nitrate of water with three atoms of constitu- 
tional oxide of copper; while the nitrate of red oxide of mercury is HgO, 
N0 5 -f HgO, or it resembles the nitrate of magnesia which has been strongly 
dried, MgO, N0 5 -f HO, (Kane.) 

Nitric acid in a solution cannot be detected by precipitating that acid in 
combination with any base, as the nitrates are all soluble, so that tests of ano- 
ther nature must be had recourse to, to ascertain its presence. A highly 
diluted solution of sulphate of indigo may be boiled without change, but on 
adding to it at the boiling temperature, a liquid containing free nitric acid, the 
blue colour of the indigo is instantly destroyed. If it is a neutral nitrate 
which is tested, a little sulphuric acid should be added to the solution, to libe- 
rate the nitric acid, before mixing it with the sulphate of indigo. It is also 
necessary to guard against the presence of a trace of nitric acid in the sulphuric 
acid. Another test of the presence of nitric acid has lately been proposed by 
de Richemont. The liquid containing the nitrate is mixed with rather more 
than an equal bulk of oil of vitriol, and when the mixture has become cool, a 
few drops of a strong solution of protosulphate of iron are added to it. Nitric 
oxide is evolved, and combines with the protosulphate of iron, producing a 
rose or purple tint even when the quantity of nitric acid is very small. One 
part of nitric acid in 24,000 of water has been detected in this manner. Free 
nitric acid also is incapable of dissolving gold-leaf, although heated upon it, 
but acquires that property when a drop of hydrochloric acid is added to it. 
But in testing the presence of this acid, it is always advisable to neutralize a 
portion of the liquor with potash, and to evaporate so as to obtain the thin 
prismatic crystals of nitre, which may be recognised by their form, by their 
cooling nitrous taste, their power to deflagrate combustibles at a red heat, and 
by the characteristic action of the acid they contain, when liberated by sul- 
phuric acid, upon copper and other metals, in which ruddy nitrous fumes are 
produced. If nitric acid be rigidly pure, it may be diluted with distilled water, 
and is not disturbed by nitrate of silver, nor by chloride of barium, the first of 
which detects the presence of hydrochloric acid by producing a white precipi- 
tate of chloride of silver; the lasft detects sulphuric acid by forming the white 
insoluble sulphate of barytes. The fuming nitric acid may be freed from hy- 
drochloric acid, by retaining it warm on a sand-bath for a day or two, when 
the chlorine of the hydrochloric acid goes off as gas. To free it from sul- 
phuric, it should be diluted with a little water, and distilled from nitrate of 
barytes; but the process for nitric acid which has been described gives it with- 
out a trace of sulphuric acid, when carefully conducted. 

Uses. — Nitric acid is sometimes used in the fumigations required for conta- 
gious diseases, particularly in wards of hospitals from which the patients are 
not removed, the fumes of this acid being greatly less irritating than those of 



CARBON. 221 

chlorine. For the purpose of fumigation pounded nitre and concentrated sul- 
phuric acid are used, being heated together in a cup. Nitric acid is par ex- 
cellence the solvent of metals, and has other most numerous and varied appli- 
cations not only in chemistry, but likewise in the arts and manufactures. 



SECTION IV. 

CARBON. 

Eq. 76.44 or 6.13; (75.6 or 6.05, Dr. Clark,) C; density of vapour {hypo- 
thetical) 421.5. 

Carbon is found in great abundance in the mineral kingdom united with 
other substances, as in coal of which it is the basis, and in the acid of car- 
bonates; it is also the most considerable element of the solid parts in both ani- 
mals and vegetables. It exists in nature or may be obtained by art, under a 
variety of appearances, and possessed of very different physical properties. 
Carbon is a dimorphous body, occurring crystallized in the diamond and gra- 
phite in wholly different forms, and when artificially produced forming several 
amorphous varieties of charcoal which are very unlike each other. 

Diamond. — This valuable gem is found throughout the range of the Ghauts 
in India, but chiefly at Golconda, in Borneo and also in Brazil. It is always 
associated with transported materials, such as rolled gravel, and has never 
been found in situ, so that its origin is doubtful, although it is now generally 
supposed to have been produced by the slow decomposition of vegetable mat- 
ter. On removing the crust with which the crystals are covered, they are 
exceedingly brilliant, refract light powerfully, and are generally perfectly trans- 
parent, although diamonds are sometimes black, blue, and of a beautiful rose- 
colour. The primitive form of diamond is the regular oc- 
tahedron, or two four-sided pyramids, of which the faces are Fig. 77. 
equi-lateral triangles, applied base to base. It is also found 
in figures bounded by 48 curved triangular faces, but can 
always be cleaved in the direction of the faces of the octo- 
hedron, which possess that particular brilliancy characteris- 
tic of the diamond. The diamond is the hardest of the gems. 
An edge of its crystal formed by flat planes only scratches 
glass, but if the edge is formed of curved faces, like the 
edge of a convex lens, it then, besides abrading the surface, produces a fissure 
to a small depth, and in the form of the glazier's diamond is used to cut glass. 
The diamond is remarkably indestructible, and may be heated to whiteness in 
a covered crucible without injury, but it begins to burn in the open air, at 
about the melting point of silver, charcoal sometimes appearing on its surface, 
and is entirely converted into carbonic acid gas. It is more quickly con- 
sumed in fused nitre, when the carbonic acid is retained by the potash; this is 
a simple mode of analyzing the diamond, by which it has been proved to be 
perfectly pure carbon. The diamond is a non-conductor of electricity. Its 
density varies from 3.5 to 3.55. 

Graphite. — This mineral, which is also known as black lead and plumbago, 
occurs in rounded masses deposited in beds in the primitive formations, par- 
ticularly in granite, mica-schist and primitive limestone. Borrowdale in Cum- 
berland is a celebrated locality of graphite, and affords the only specimens which 
are sufficiently hard for making pencils. It is occasionally found crystallized in 
plates which are six-sided tables. Graphite may also be produced artificially, 
by putting an excess of charcoal in contact with fused cast iron, when a portion 

19* 




222 CARBON. 

of the carbon dissolves, and separates again on cooling, in the form of large and 
beautiful crystalline leaflets. In the condition of graphite, carbon is perfectly 
opaque, soft to the touch, possessed of the metallic lustre, and of a specific 
gravity about 2.5. It always contains a small quantity of iron, often amounting 
to 5 per cent, but in some specimens, as in those from Barreros in Brazil, not 
more than a trace, which is to be considered an accidental constituent, and not 
essentia] to the mineral. Neither in the form of diamond nor graphite does 
carbon exhibit any indication of fusion or volatility under the most intense heat. 
Anthracite is nearly pure carbon, but always contains a portion of hydrogen, 
and is more analogous to coal than to graphite. 

Charcoal — Owing to its infusibility carbon presents itself under a variety of 
aspects, according to the structure of the substance from which it is derived,, 
and the accidental circumstances of its preparation. The following are the 
principal varieties: gas-carbon, lamp black, wood charcoal, coke, and ivory black. 

1°. Gas-carbon has the metallic lustre, and a density of 1.76; it is compact, 
generally of a mammillated structure, but sometimes in fine fibres, and con- 
siderably resembles graphite, but is too hard to give a streak upon paper. It 
is the product of a slow deposition of carbon from coal gas at a high temperature 
and is frequently found to line the gas retorts to a considerable thickness, and 
to fill up accidental fissures in them.* 

2°. Lamp black is the soot of imperfectly burned combustibles such as tar or 
resin. Carbon is deposited in a powder of the same nature, when alcohol 
vapour or a volatile oil is transmitted through a porcelain tube at a red heat ; 
and the lustrous charcoal which is obtained on calcining starch, sugar and 
many other organic substances, which fuse and afford a bright vesicular carbon 
of a metallic lustre, is possessed of the same characters. It is deficient in an 
attraction for organic matters in solution, which ordinary charcoal possesses. 

3°. Wood charcoal. Wood was found by Karsten to lose 57 per cent, of its 
weight when thoroughly dried at 212° and 10 per cent, more at 304°. The 
remaining 33 parts of baked wood afforded, when calcined, 25 of charcoal, 
while 100 parts of the same wood calcined, without being previously dried, left 
only 14 per cent, of carbon. It is the absence of this large quantity of water 
which causes the heat of burning charcoal to be so much more intense than that 
of w r ood. When calcined at a high temperature, charcoal becomes dense, hard 
and less inflammable. The knots in wood sometimes afford a charcoal which 
is particularly hard, and is used in polishing metals, but it contains silica. From 
the minuteness of its pores, the charcoal of wood absorbs many times its volume 
of the more liquefiable gases, such as ammoniacal gas, hydrochloric acid, sul- 
phuretted hydrogen and carbonic acid, condensing 35 volumes of the last. It 
also absorbs moisture with avidity from the atmosphere, and other condensible 
vapours, such as odoriferous effluviae. From this last property freshly calcined 
charcoal, when wrapt up in clothes which have contracted a disagreeable odour, 
destroys it, and has a considerable effect in retarding the putrefaction of organic 
matter with which it is placed in contact. Water is also found to remain sweet, 
and wine to be improved in quality if kept in casks of which the inside has been 
charred. In the state of a coarse powder wood charcoal is particularly appli- 
cable as a filter for spirits, which it deprives of the essential oil which they 
contain. It is much less destructible by atmospheric agencies than wood, and 
hence the points of stakes are often charred, before being driven into the ground, 
in order to preserve them. 

4°. The coke of those species of coal, which do not fuse when heated, is a 
remarkably dense charcoal, considerably resembling that of wood, and of great 
value as fuel from the high temperature which can be produced by its com- 

* Dr. Colquhoun, Annals of Philosophy, New Scries, vol. 12, p. 1. 



CARBON. 



223 



bustion. When burned it generally leaves 2 or 3 per cent, of earthy ashes, 
while the ashes from wood charcoal seldom exceed 1 per cent. 

5°. Ivory black, bone-charcoal and animal charcoal are names applied to 
bones calcined or converted into charcoal in a close vessel. The charcoal thus 
produced is mixed with not less than 10 times its weight of phosphate of lime, 
and being in a state of extreme division, exposes a great deal of surface. It 
possesses a remarkable attraction for organic colouring matters, and is exten- 
sively used in withdrawing the colouring matter from syrup, in the refining of 
sugar, from the solution of tartaric acid, and in the purification of many other 
organic liquors. The usual practice, which was introduced by Dumont, is to 
filter the liquid to be discoloured, through a bed of this charcoal, in grains of the 
size of those of gunpowder, and of two or three feet in thickness. It is found 
that the discolouring power is greatly reduced by dissolving out the phosphate 
of lime from ivory black by an acid, although this must be done in certain 
applications of it, as when it is used to discolour the vegetable acids. A char- 
coal possessed of the same valuable property even in a higher degree for its 
weight, is produced by calcining dried blood, horns, hoofs, clippings of hides, in 
contact with carbonate of potash, and washing the calcined mass afterwards 
with water. Even vegetable matters afford a charcoal, possessed of consider- 
able discolouring power, if mixed with chalk, calcined flint or any other earthy 
powder, before being carbonized. One hundred parts of pipe clay made into a 
thin paste with water, and well mixed with 20 parts of tar and 500 of coal 
finely pulverized, have been found to afford, after the mass was dried and ignited 
out of contact with air, a charcoal which was little inferior to bone-black in 
quality. When charcoal which has been once used in such a filter, is calcined 
again, it is found to possess very little discolouring power. This is owing to the 
deposition upon its surface of a lustrous charcoal, of the lamp black variety, 
produced by the decomposition of the organic colouring matters, which has 
little or no discolouring power. But if the charcoal of the sugar filters be 
allowed to ferment, the foreign matter in it is destroyed; and if afterwards well 
washed with water and dried, before being calcined, it will be found to recover 
a considerable portion of its original discolouring power. 

Bussy has constructed, from observation, the following table of the efficiency 
of the different charcoals. These substances are compared with ivory black, 
as being the most feeble species, although this is superior by several degrees to 
the best wood charcoal. The relative efficiency, it will be observed, is not the 
same for two different kinds of colouring matter: 



Species of Charcoal 


Relative Decolor- 


Relative Decolor 


same weight. 


ation of sulphate 
of indigo. 


ation of Syrup. 


B.ood charred with carbonate of potash 


50 


20 


Blood charred with chalk .... 


18 


11 


Blood charred witli phosphate of lime . 


12 


10 


Glue charred with carbonate of potash 


36 


15.5 . 


White of ejrg- charred with the same . 


34 


15.5 


Gluten chaired with the same 


10.6 


8.8 


Charcoal from acetate of potash 


5.6 


4.4 


Charcoal from acetate of soda 


12 


8.8 


Lamp black, not calcined .... 


4 


3.3 


Lamp black calcined with carbonate of potash. 


15.2 


10.6 


Bone charcoal, after the extraction of the earth of bones 






by an acid, and calcination with potash 


45 


20 


Bone charcoal treated with an acid 


1.87 


1.6 


Oil charred with the phosphate of lime 


2 


1.9 


Bone charcoal, in its ordinary state. . 


1 


1 



224 CARBON. 

This remarkable action of charcoal in withdrawing matters from solution is 
certainly an attraction of surface, but it is capable notwithstanding, of over- 
coming chemical affinities of some intensity. The matters remain attached to 
the surface of the charcoal, without being decomposed or altered in nature. 
For if the blue sulphate of indigo be neutralized and then filtered through char- 
coal, the whole colouring matter is retained by the latter, and the filtered liquid 
is colourless. But a solution of caustic alkali will divest the charcoal of the blue 
colouring matter, and carry it away in solution. Other substances also are 
carried down by animal charcoal, besides animal matters. Lime from lime 
water, iodine from solution in iodide of potassium, soluble subsalts of lead, and 
metallic oxides dissolved in ammonia and caustic potash ; but it has little or no 
action upon most neutral salts. The charcoal is apt with time to react upon 
the substance it carries down, probably from their closeness of contact, reducing 
the oxide of lead, for instance, in a short time to the metallic state. 

Carbon is chemically the same under all these forms. This element cannot 
be crystallized artificially by the usual methods of fusion, solution or sublima- 
tion, if we except its solution in cast iron, which gives it in the form of gra- 
phite and not of the diamond. It is chemically indifferent to most bodies 
at a low temperature, but combines directly with some metals by fusion 
and forms carburets. When heated to low redness it burns readily in air or 
oxygen, forming a gaseous compound carbonic acid, which when cool has ex- 
actly the bulk of the original oxygen. With half the proportion of oxygen in 
carbonic acid, carbon forms a protoxide, carbonic oxide gas. This gas being 
supposed similar to steam or to nitrous oxide in its constitution, will be com- 
posed of 2 vols, of carbon vapour and 1 vol. of oxygen gas condensed into 2 
volumes, an assumption upon which the density of carbon vapour, which 
there are no means of determining experimentally, is usually calculated, and 
made about 421.5; the combining measure of this vapour containing 2 volumes 
(page 111.) It has been inferred from the results of recent organic analysis, 
that the number 76.44, fixed upon by Berzelius as the equivalent of carbon is 
too high, and that 75.6 is near the truth.* 

Uses. — Several valuable applications of this substance have already been 
incidentally described. Carbon may be said to surpass all other bodies what- 
ever in its affinity for oxygen at a high temperature; and being infusible, easily 
got rid of by combustion, and forming compounds with oxygen which escape 
as gas, this body is more suitable than any other substance to effect the reduc- 
tion of metallic oxides, that is, to deprive them of their oxygen, and to pro 
duce from them the metal with the properties which characterize it. 



CARBONIC ACID. 

Eq. 276, or 22.13; C0 2 ; density 1524.1; f~TH * 

This gas was first discovered to exist in lime-stone and the mild alkalies, 
and to be expelled from them by heat and the action of acids by Dr. Black, 
and was named by him Fixed Air. He also remarked that the same gas is 
formed in respiration, fermentation and combustion; it was afterwards proved 
to contain carbon by Lavoisier. 

Preparation. — Carbonic acid is readily procured by pouring hydrochloric 
acid of sp. gr. 1. 1, upon fragments of marble contained in a gas bottle, or by 
the action of diluted sulphuric acid upon chalk. A gas comes off with effer- 

* By Dr. Clark; see also Dumas; Phil. Mag. 3rd. series vol. 14, p. 153, and the account 
of certain analyses by Mr. Fownes, id. vol. 15, p. 62. 



CARBONIC ACID. 225 

vescence, which may be collected at the water trough, but cannot be retained 
long over water without considerable loss, owing to its solubility. When 
generated in the close apparatus of M. Thilorier for the purpose of liquefying 
it, this gas is evolved from bicarbonate of soda and sulphuric acid. 

Properties. — This gas extinguishes flame, does not support animal life, and 
renders lime-water turbid. Its density is considerable, being 1524, or a half 
more than that of air, the gas containing 2 volumes of the hypothetical carbon 
vapour and 2 volumes of oxygen, condensed into 2 volumes, which form the 
combining measure. Cold water dissolves rather more than an equal volume 
of this gas; the solution has an agreeable acidulous taste, and sparkles when 
poured from one vessel into another. It communicates a wine-red tint to lit- 
mus paper, which disappears again when the paper dries; when poured into 
lime-water it first throws down a white flaky precipitate of carbonate of lime or 
chalk; which ic afterwards redissolves if the solution be added in excess. The 
quantity of this gas which water takes up is found to be exactly proportional 
to the pressure; a very large volume of the gas is forced into soda, magnesia 
and other aerated waters, much of which escapes on removing the pressure 
from these liquids. 

This gas was liquefied by Mr. Faraday, whose method has been followed 
by Thilorier in an apparatus by which the liquid acid is procured in large 
quantity, which is constructed with some improvements by Mr. Addams of 
Kensington. It consists of two similar cylindrical vessels of strong sheet 
iron, calculated to resist a bursting pressure of 60 atmospheres, in one of 
which several pounds of bicarbonate of soda are decomposed at once by an 
equivalent quantity of sulphuric acid. The gas confined within this generating 
vessel is afterwards allowed to communicate with the second cylinder or con- 
denser, by means of a copper tube and stopcock of nice construction; and the 
charge is repeated several times in succession, till two or three pints of the li- 
quid acid are collected in the receiver. When this liquid is allowed to escape 
from the receiver by a small jet, a portion of it is frozen by its own evapora- 
tion, and forms a white soft mass, like snow, which may be handled and does 
not evaporate very rapidly, owing to its low conducting power, although its tem- 
perature cannot be more than — 148°. With a little ether the solid acid forms 
a semifluid mass, by means of which mercury can be frozen in considerable 
quantity. The sp. gr. of the liquid is 0.83 at 32°; it dilates remarkably from 
heat, its expansion being four times greater than that of air, 20 volumes of the 
liquid at 32° becoming 29 at 86°, and its density varying from 0.9 to 0.6 as its 
temperature rises from, — 4° to 86°. It mixes in all proportions with ether, al- 
cohol, naphtha, oil of turpentine and bisulphuret of carbon, but is insoluble in wa- 
ter and fat oils. Its compound with alcohol may be frozen, and melts at — 135°, 
which is the lowest point fixed with accuracy in the descending scale of tempe- 
rature.* Mr. Addams has made careful experiments upon the elasticity of the 
vapour of this liquid, at different temperatures, of which the following are the 
results: 



ELASTIC FORCE OF LIQUID CARBONIC ACID. 



Temperature. 

0° 

10 . 
30 . 
32 . 


Pou 


ids per 
inch. 

280 
300 
398 
413 


square 


Atmospheres of 
15 pounds each. 

. 18.1 
. 20 
. 26.5 
. 27.6 



* Thilorier, An. de Ch. et de Ph. t. 60, p. 427. 



226 CARBON. 

50 . . . .520 . . . . 34.7 
100 .... 935 ... 62.3 

150 . . . 1496 .... 99.7 

Potassium heated in a small glass bulb blown upon a tube, through which 
gaseous carbonic acid is transmitted, undergoes oxidation, and liberates carbon, 
the existence of which in the gas may thus be shown. But burning phos- 
phorus, sulphur and other combustibles are immediately extinguished by car- 
bonic acid, and the combustion does not cease from the absence of oxygen 
only, but from a positive influence in checking combustion which this gas 
exerts, for a lighted candle is extinguished in air containing no more than a 
fourth of its volume of carbonic acid. It is generally believed that any mix- 
ture of carbonic acid and air will support the respiration of man, which will 
maintain the flame of a candle, and therefore a lighted candle is often let down 
into wells or pits suspected to contain this gas, to ascertain whether they are 
safe or not. But although air in which a candle can burn may not occasion 
immediate insensibility, still the continued respiration for several hours of air 
containing not more than 1 or 2 per cent, of carbonic acid, has been found to 
produce alarming effects (Broughton.) The accidents from burning a pan of 
charcoal in close rooms are occasioned by this gas. It acts as a narcotic poi- 
son upon the system. A small animal thrown into convulsions from the re- 
spiration of this gas, may be recovered by sudden immersion in cold water. 

Carbonic acid is thrown off from the lungs in respiration, as may be proved 
by directing a few expirations through lime water. The air of an ordinary 
expiration contains on an average, as observed by Dr. Prout, 3.45 per cent, of 
the gas, and the proportion varies from 3.3 to 4.1 per cent, being greatest at 
noon, and least during the night. Carbonic acid is also a product of the vinous 
fermentation, and is the cause of the agreeable pungency of beer, ale and 
other fermented liquors, which become stale when exposed to the air from the 
loss of this gas. It also exists in all kinds of well and spring water, and con- 
tributes to their pleasant flavour, for water which has been deprived of its 
gases by boiling is insipid and disagreeable. Carbonic acid is also largely 
produced by the combustion of carbonaceous fuel, and appears to exist in con- 
siderable quantity in the earth, being discharged by active volcanoes, and from 
fissures in their neighbourhood long after the volcanoes are extinct. The Grotto 
del Cane in Italy owes its mysterious properties to this gas, and many mineral 
springs, such as those of Tunbridge, Pyrmont and Carlsbad are highly charged 
with it. It comes thus to be always present in the atmosphere in a sensible 
although by no means considerable proportion, (page 209.) 

Carbonic acid combines with bases, and forms the class of carbonates. The 
hydrate of this acid seems incapable of existing in an uncombined state, but it 
exists in the alkaline bicarbonates, which are double carbonates of water and 
the alkali. If this hydrate were formed, it would probably be found analo- 
gous to the crystallized carbonate of magnesia, of which the formula is MgO, 
C0 2 +HO-(-2HO, and also the same with another 2HO; the salt of magnesia 
of most acids resembling the salt of water. Carbonate of lime, in the hydrated 
condition, has a similar formula. But the carbonates exhibit little affinity for 
water, and are generally anhydrous. Those of the alkalies retain a strong 
alkaline reaction, owing to the weakness of this acid, and the carbonates gene- 
rally are decomposed with effervescence by all other acids, except hydro- 
cyanic. 

Uses. — Carbonic acid is not used in the arts, except in the preparation of 
aerated waters. The strong vessels in which the impregnation is effected, 
should be of copper well tinned, and not of iron, as with the concurrence of 
water carbonic acid acts strongly upon that metal. It is sometimes desirable 



CARBON. 227 

to remove carbonic acid from air or other gaseous mixtures, and this is gene- 
rally done by means of caustic alkali or lime-water. When very dry, or so 
humid as to be actually wet, the hydrate of lime absorbs this gas with much 
less avidity than when of a certain degree of dryness, in which it is not so 
dry as to be dusty, but at the same time not sensibly damp. The dry hy- 
drate may be brought at once to this condition, by mixing it intimately with 
an equal weight of glauber's salt, in fine powder; and this mixture in a stratum 
of not more than an inch in thickness intercepts carbonic acid most completely, 
and may rise in temperature to above 200° from the rapid absorption of the 
gas. It is quite possible to respire through a cushion of that thickness, filled 
with this mixture, and such an article might be found useful by parties enter- 
ing an atmosphere overcharged with carbonic acid, like that of a coal mine 
after the occurrence of an explosion of fire damp. 

Carbonic acid is the highest degree of oxidation of which carbon is suscep- 
tible; but another oxide of carbon exists containing less oxygen. 



CARBONIC OXIDE. 
Eq. 176, or 14.13; CO; density 972.85 



Priestley is the discoverer of this gas, but its true nature was first pointed 
out by Cruikshanks, and about the same time by Clement and Desormes. 

Preparation. — Carbonic acid is readily deprived of half its oxygen, at a red 
heat, by a variety of substances, and so reduced to the state of carbonic oxide. 
The latter gas may therefore be obtained by transmitting carbonic acid over 
red hot fragments of charcoal contained in an iron or porcelain tube; or by cal- 
cining chalk mixed with 1— 4th of its weight of charcoal in an iron retort. It 
is likewise prepared by gently heating crystallized oxalic acid with 5 or 6 
times its weight of strong oil of vitriol in a glass retort. The latter process 
affords a mixture of equal volumes of carbonic acid and carbonic oxide, the 
elements of oxalic acid being carbon and oxygen in the proportion to form 
these gases, and this acid being incapable of existing except in combination 
with water or some other base. Now the sulphuric acid unites with the water 
of the cr. oxalic acid, and the acid being set free is instantly decomposed. 
The gas of all these processes contains much carbonic acid, of which it may 
be deprived, by washing it with milk of lime, or by transmitting the gas 
through a tube filled with the mixture of hydrate of lime and glauber's salt. 

Properties. — This gas, as has already been stated, is presumed to contain 
2 volumes of carbon, and 1 volume of oxygen, condensed into 2 volumes so 
that its combining measure is 2 volumes. It is not more soluble in water than 
atmospheric air, and has never been liquefied. It is easily kindled and burns 
with a pale blue flame, like that of sulphur, combining with half its volume of 
oxygen, and forming carbonic acid, which retains the original volume of the 
carbonic oxide. This combustion is often witnessed in a coke or charcoal 
fire. The carbonic acid produced in the lower part of the fire, is converted 
into carbonic oxide, as it passes up through the red hot embers, and afterwards 
burns above them with a blue flame, where it meets with air. 

Carbonic oxide is a neutral body, like water, and combines directly with 
only a very few substances. It unites with an equal volume of chlorine under 
the influence of the sun's rays, and forms phosgene gas or chlorocarbonic acid. 
It is also absorbed by potassium gently heated, and that metal is employed to 
separate carbonic oxide from a mixture of hydrogen and gaseous hydrocar- 
burets, as in the analysis of coal gas. But carbonic oxide is supposed to 



228 BORON. 

exist in a greater number of compounds, and to be the radical of a series, of 
which the following substances are imagined to be members: 



CARBONIC OXIDE SERIES. 

Carbonic oxide. - - - - - CO 

Carbonic acid. CO-fO 

Chlorocarbonic acid. - CO-fCl 

Oxalic acid. 2CO + 

Oxamide. - - - - - - 2CO + NH 2 

Oxicarburet of potassium. - 7CO-J-3K 

Croconic acid. 5CO + H 

Mellitic acid - - - - - - 4CO+H 

In these compounds carbonic oxide is represented as playing the part of a 
simple substance, and forming a variety of products by uniting with oxygen, 
chlorine, hydrogen and other elements. 

Oxalic, mellitic and croconic acids are sometimes enumerated as oxides of 
carbon, along with carbonic acid and carbonic oxide, but as the former bodies 
always exist in a state of combination and cannot be isolated, they have not 
an equal claim to the same early consideration as the latter compounds. 



SECTION V. 

BORON. 
Eq. 136.25, or 10.91; B; density of vapour (hypothetical) 751; 



Boron is an element having some analogy to carbon, but sparingly diffused 
in nature. It is never found, except in combination with oxygen as boracic 
acid, of which the salt of soda has long been brought to Europe from India in 
a crude state, under the name of tinkal and termed borax when purified. The 
impure borax or tinkal forms a saline incrustation in the beds of certain small 
lakes in an upper province of Thibet, which dry up during summer. But the 
most considerable of the present sources of boracic acid are the hot lagoons of 
a district in Tuscany, which are charged with the free acid, from the conden- 
sation in them of vapours of a volcanic origin. Boracic acid is likewise found 
in the hot springs of Lipari. It is a constituent also of several minerals, of 
which datolite and boracite are the most remarkable. Boron was first disco- 
vered by Sir H. Davy in 1807, by exposing boracic acid to the action of a 
powerful voltaic battery, and was afterwards obtained by Gay-Lussac and 
Thenard in greater quantity, by heating boracic acid with potassium. 

Preparation. — Boron is prepared with greatest advantage from a combina- 
tion of fluoride of boron and fluoride of potassium, which is obtained on satu- 
rating hydrofluoric acid with boracic acid, and adding to it drop by drop, the 
fluoride of potassium. This compound which is of slight solubility, is col- 
lected on a filter, and dried at an elevated temperature, but which should not 
reach a red heat. Equal weights of this compound and potassium are mixed 
together in a cylinder or tube of iron, closed at one end, which is gently 
heated, and the mixture stirred with an iron rod, till the potassium is melted. 
Heated more strongly by a spirit lamp, the mass evolves heat and becomes 
red hot; the potassium combines with the fluorine, and a mixture is obtained 



BORACIC ACID. 229 

of boron and the fluoride of potassium. On treating this with water, the 
fluoride of potassium dissolves, and the boron remains insulated. In washing 
it farther, instead of pure water, which acts upon boron, a solution of sal-am- 
moniac should be employed, which does not dissolve that body, and the sal- 
ammoniac remaining in the boron may be taken up by alcohol. 

Properties. — Thus prepared, boron is obtained in the form of a greenish 
brown powder, without the metallic lustre, which becomes hard and assumes 
a deeper colour, when ignited in vacuo, or in gases which do not combine 
with it, but undergoes no farther change. Heated in atmospheric air or oxy- 
gen it burns with a vivid light, scintillating powerfully, and forms boracic 
acid. Nitric acid and many other substances also oxidate it easily, and always 
produce that compound. Fused with carbonate of potash, it decomposes the 
carbonic acid, and gives borate of potash, carbon being liberated. Boron is 
not known to possess any other degree of oxidation. Boron combines with 
sulphur, with the disengagement of light, when heated in the vapour of that 
substance; and it takes fire spontaneously in chlorine, and forms a gaseous 
chloride of boron, of which the formula is BC1 3 , and the density 4035. This 
gas is formed of 2 vols, of boron vapour and 6 of chlorine, condensed into 3 
vols, which are its combining measure. It may likewise be formed, by trans- 
mitting chlorine gas over a mixture of boracic acid and charcoal, ignited in a 
porcelain tube. A corresponding fluoride of boron is evolved from boracic 
acid, ignited with the fluoride of calcium or fluor spar, with the formation of 
borate of lime. The density of this fluoride is 2308. 

Boracic acid. — This acid is generally prepared by dissolving the salt borax 
at 212° in four times its weight of water, the solution is filtered hot, and a 
quantity of oil of vitriol immediately added to it, equal to one fourth of the weight 
of the borax. The sulphuric acid unites with the soda, and forms sulphate of 
soda, which continues in solution, while the boracic acid separates in thin shining 
crystalline plates, on cooling. These plates are drained, and being sparingly 
soluble, may be washed with cold water, and afterwards redissolved in boiling 
water and made to crystallize anew. The boracic acid still retains a small 
quantity of sulphuric acid, probably in a state of chemical combination, and if 
required of absolute purity must be fused at a red heat in a platinum crucible, 
then dissolved again and crystallized. The density of the vitrefied acid is 1.83. 
Boracic acid has a weak taste, which is scarcely acid, and affects blue litmus 
like carbonic acid, imparting to it a wine- red tint, and not that clear red, free 
from purple, which the stronger acids produce. It renders yellow turmeric 
paper, brown, like the alkalies. The crystals are a hydrate, and contain three 
equivalents of water, of which the formula is HO, BO., 4-2HO. At 60° it re- 
quires 25.66 times its weight of water to dissolve it, but only 2.97 times at 212°. 
With the assistance of the vapour of water, it is said to be slightly volatile, but 
alone it is fixed, and fuses, under a red heat, into a transparent glass. The 
hydrated acid dissolves in alcohol, and the solution burns with a fine green 
flame. At the temperature of the air, boracic acid is relatively a feeble acid, 
but at a red heat it displaces the greater number of those acids which are more 
volatile than itself It communicates fusibility to many substances in uniting 
with them, and generally forms a glass. On this account borax is much used 
as a flux. 

Borates. — Boracic acid is remarkable for the variety of proportions in which 
it unites with the alkalies; all these borates have an alkaline reaction like the 
carbonates. The relative proportions of oxygen and boron in boracic acid are 
known, but the number of equivalents of these elements in this acid is not so 
certain. Dumas inferred from the density of the chloride that it is a terchloride, 
and boracic acid, which corresponds, will therefore consist of 3 eq. oxygen to 1 
eq. boron, and its formula be B0 3 . This makes borax the biborate of soda. 
20 



230 SILICON. 

SECTION VI. 

SILICON. 

Syn. Silicium. Eq. 27? '-31 or 22.22; Si; density of vapour {hypothetical) 

1529; rn- 

Silica or siliceous earth, the oxide of the present element, is the most abundant 
of all the matters which compose the crust of the globe. It constitutes sand, the 
varieties of sandstone and quartz rock, and enters into felspar, mica and a pro- 
digious variety of minerals, which form the basis of other rocks. 

Preparation. — Silica may be decomposed by heating it with potassium, which 
deprives it of oxygen ; but a better process for obtaining silicon, is to heat the 
double fluoride of silicon and potassium, with 8 or 9-10ths of its weight of po- 
tassium, with the same precautions as in the preparation of boron. The ma- 
terials, however, in this case may be heated in a glass tube, as well as in an 
iron cylinder. The double fluoride employed, is prepared by neutralizing 
fluosilicic acid with potash. A different process is suggested by Berzelius, 
which consists in heating potassium in a tube of hard glass with a small bulb 
blown upon it, which is filled with the vapour of the fluoride of silicon, supplied 
from the ebullition of that liquid contained in a small retort connected with the 
glass tube. The potassium burns in this vapour, and at the end, silicon is found, 
with fluoride of potassium, in the place of the metal (Traite, t. 1, p. 137.) But 
the silicon from all these processes is always in combination with a little po- 
tassium, and mixed with a little fluoride of silicon and potassium unreduced. 
Hence, on applying cold water to the mass, hydrogen gas is disengaged, and 
potash formed, and the silicon separates. The potash thus produced can, with 
the aid of hot water, dissolve the silicon, which then oxidates and becomes 
silica, so that cold water only must be employed to wash the silicon, which may 
be thrown upon a filter. After a time, the liquid which passes has an acid re- 
action, which arises from its dissolving an acid double fluoride of silicon and 
potassium, of sparing solubility, which has escaped decomposition, and is mixed 
with the silicon. The washing is continued so long as the water dissolves any 
thing. 

Properties. — The silicon which is thus obtained is, in its pure state, a dull 
brown powder, which soils the fingers, and when heated in air or oxygen, in- 
flames and burns, but is never more than partially converted into silica. It 
may be ignited strongly in a covered crucible without loss, and then shrinks in 
dimensions, acquires a deep chocolate colour, and becomes so dense as to sink 
in oil of vitriol. By this ignition the properties of silicon are altered to a degree 
which is very remarkable in a simple substance. It was previously readily 
soluble in hydrofluoric acid, with evolution of hydrogen, and in caustic potash, 
but it is now no longer acted upon by that or any other acid, nor by alkalies. 
The ignited silicon also refuses to burn in air or oxygen even when intensely 
heated by the blow-pipe flame. Charcoal, it will be remembered, is more dense 
and less combustible after being strongly heated ; but that substance is not 
altered by heat to the same extent as silicon. Mixed and heated with dry car- 
bonate of potash, silicon in any condition is oxidated completely, its action upon 
the carbonic acid of the salt being attended with ignition, and carbon liberated. 
Silicon burns when heated in sulphur vapour, and forms a sulphuret, which 
water dissolves, but decomposes at the same time, sulphuretted hydrogen and 
silica being produced, and the last, despite its usual insolubility, retained in 
solution. Silicon likewise burns in chlorine; and the chloride of silicon may be 



SILICA. 231 

otherwise formed by transmitting chlorine over a mixture of charcoal and silica 
ignited in a porcelain tube. The silica is decomposed by neither charcoal nor 
chlorine singly, but acting together upon the silica, these bodies produce car- 
bonic oxide and chloride of silicon. This compound is a volatile liquid, of which 
the formula is SiCl 3 ; that of the sulphuret of silicon SiS 3 . 

Silica or Silicic Acid, Si0 3 . — This earth, which is the only oxide of silicon, 
constitutes a number of minerals, nearly in a state of purity, such as rock- 
crystal, quartz, flint, sandstone, the amethyst, calcedony, cornelian, agate, opal, 
&c. The first chemical examination of its properties and compounds is due to 
Bergman. 

Preparation. — Silica may be had very nearly, if not absolutely pure, by 
heating a colourless specimen of rock crystal to redness and throwing it into 
water, after which treatment the mineral may easily be pulverized. It is ob- 
tained in a state of more minute division, by transmitting the gaseous fluoride 
of silicon (fluosilicic acid) into water ; or by the action of acids upon some of 
the alkaline compounds of silica. Equal parts of carbonate of potash and car- 
bonate of soda may be fused in a platinum crucible, at a temperature which is 
not high ; and pounded flint or any other siliceous mineral, thrown by little and 
little into the fused mass, dissolves in it with an effervescence due to the escape 
of carbonic acid gas. The addition of the mineral may be continued so long 
as it determines this effervescence. The mass being allowed to cool, is after- 
wards dissolved in water acidulated with hydrochloric acid, which takes up the 
silica as well as the alkalies; the liquor is filtered and then evaporated to dry- 
ness. The silica may contain a little peroxide of iron or alumina, to dissolve 
which the saline mass, when perfectly dry, is moistened with concentrated 
hydrochloric acid, and after two hours the acid mass is washed with hot water. 
The silica remains undissolved ; it may be dried well and ignited. 

Properties. — Silica so prepared is a white, tasteless powder, which is rough 
to the touch, and feels gritty between the teeth. It is extremely mobile when 
heated, and is thrown out of a crucible, at a high temperature, by the slightest 
breath of wind. It is absolutely insoluble in water, acids and most liquids. Its 
density is 2.66. The heat of the strongest wind-furnace is not sufficient to fuse 
silica, but it melts into a limpid colourless glass in the flame of the oxihydrogen 
blow-pipe. Silica is found frequently crystallized, its ordinary form being a 
six-sided prism terminated by a six-sided pyramid, as in rock-crystal. Some- 
times the prism is very short or disappears entirely, and the pyramid only is 
seen, as in ordinary quartz. 

Soluble Silicic Acid. — The preceding description applies to silica after it 
has been dried or heated, but silica can also be obtained in a state in which it 
is soluble in dilute acids and even in water. The oxidation of the sulphuret 
of silicon, in water, gives silica in this condition; the solution when concen- 
trated, becomes a gelatinous mass, like size. When the gaseous fluoride of 
silicon is absorbed by water, silica separates in large quantity in that gelatinous 
condition, and this jelly is soluble in water although it requires a large quan- 
tity to dissolve it. The solution of silica was found by Berzelius to be insipid, 
and not to redden litmus; by evaporation of the liquor the silica is deposited 
in the form of an earthy mass without a trace of crystallization, and capable 
of dissolving again in water. It is observed, however, that when sulphuric 
or hydrochloric acid is added to the solution during evaporation, the silica ob- 
tained is no longer the soluble, but the former insoluble variety. The fixed 
alkalies and their carbonates, it is curious, effect a transmutation of the oppo- 
site kind, for when insoluble silica is boiled with them, it is gradually con- 
verted into the soluble species and dissolves. Berzelius finds that this change 
supervenes, without decomposition of the alkaline carbonate or any escape of 
carbonic acid. The alkali in this solution may be saturated completely with 



232 SULPHUR. 

an acid, without any silica precipitating, which proves that that body is dis- 
solved in the water and not in the alkaline carbonate. 

The water of springs and wells always contains a little soluble silica, which 
can only be obtained by evaporating the water to dryness. In some mineral 
waters the proportion of silica is very considerable, and it is often associated 
with an alkaline carbonate, as in the hot alkaline spring of Reikum in Iceland, 
and in the boiling jets of the Geyser, which deposite about their crater an in- 
crustation of silica. There can be no doubt likewise that much of the crys- 
talline quartz in nature besides all the agates, calcedonies and siliceous petri- 
factions have been formed from an aqueous solution. 

The soluble silica seems to exist in the class 'of minerals called zeolites, 
which also contain water, and many of which dissolve entirely in dilute hy- 
drochloric acid. But it may be obtained from any silicate by fusing it with an 
alkaline carbonate, and afterwards dissolving in dilute acid. The solution, on 
concentration, gives a transparent jelly, which is highly tenacious, and cracks 
on drying, forming a mass like gum. When completely dried in the air, the 
mass is no longer soluble in water or acids. It contains a small quantity of 
water, which, however, according to Berzelius is hygroscopic; silica affording 
him no definite hydrates, like those of other acids. But I should still be dis- 
posed to look to the state of hydration, however feebly the water may be re- 
tained, for an explanation of the differences between the soluble and insoluble 
varieties of silica. Hydrofluoric acid is the only acid which dissolves silica 
in both conditions. 

Silicates. — Although silica has no acid reaction, it is certainly an acid, and 
is indeed capable of displacing the most powerful of the volatile acids at a 
high temperature. It is capable of uniting with metallic oxides, by way of 
fusion, in a great variety of proportions. Its compounds with excess of alkali, 
are caustic and soluble, but those with an excess of silica are insoluble, and 
form the varieties of glass, which will be noticed under the silicate of soda. 
With alumina it forms the less fusible compounds of porcelain and stoneware 
which will be noticed under that earth. A large number of mineral species 
are also earthy silicates. It seems probable that silicic, like phosphoric acid, 
forms several classes of salts, of which those containing the largest number of 
atoms of base are the most soluble, and afford, when decomposed, the soluble 
silica. At the same time some difference may exist between the silicic acid 
itself, as it exists in these different classes of salts, such as there is between 
ignited and unignited silicon. 



SECTION VII. 

SULPHUR. 

Eq. 201.17 or 16.12; S; density 6648; combining measure l-3rd. volume. 

This element is exhaled in large quantity from volcanoes, either in a pure 
state or in combination with hydrogen, and by condensing in fissures forms 
sulphur veins, from which the greater part of the sulphur of commerce is de- 
rived. It exists also in combination with many metals, as iron, lead, copper, 
zinc, &c; and is extracted in considerable quantity from bisulphuret of iron 
or iron pyrites. Sulphur is classed with oxygen; and the higher sulphurets 
resemble peroxides in losing a portion of their sulphur, as we have seen some 
of the latter lose a portion of their oxygen, when strongly heated. Sulphur 
is likewise extensively diffused, as a constituent of the sulphuric acid in gyp- 



SULPHUR. 233 

sum and other native sulphates. This element also enters the organic king- 
dom, being invariably associated in minute quantity with albumen, whether 
fluid in the egg or solid in the hair. 

Properties. — Sulphur is found in commerce in rolls, which are formed by 
pouring melted sulphur into cylindrical moulds, and also in the form of a fine 
crystalline powder, the flowers of sulphur, which are obtained by throwing 
the vapour of sulphur into a close apartment, of which the temperature is below 
the point of fusion of that substance, and in which the sulphur therefore con- 
denses in the solid form and in minute crystals, just as watery vapour does in 
the atmosphere below 32°, in the form of snow. The purity of the flowers 
is more to be depended upon than that of roll sulphur. Sulphur is insipid, 
and generally inodorous, but acquires an odour when rubbed; it is very friable, 
a roll of it generally emitting a crackling sound, and sometimes breaking, when 
held in the warm hand. Its specific gravity is 1.98. It fuses at 226°, and 
between that temperature and 280° forms a clear liquid of an amber colour. 
But about 320° it begins to thicken, assumes a reddish tint, and if the heat be 
continued, becomes so thick that the vessel may be inverted without the sul- 
phur flowing out. This change is not occasioned by an increase of density, 
for fluid sulphur continues to expand with the temperature. Thrown into 
water, while in this condition, sulphur forms a mass which remains soft and 
transparent for some time after it is perfectly cool, and may be drawn into 
threads which have considerable elasticity. From 482° to its boiling point 
601°, it becomes again more fluid, and if allowed to cool returns through the 
same conditions, becoming again very fluid, before freezing. Sulphur has 
considerable volatility, beginning to rise in vapour before it is completely 
fused. At its boiling point it forms a vapour of an orange colour, and distils 
over unchanged. The density of this vapour is very considerable, being ob- 
served to lie between 6510 and 6617 by Dumas, and to be 6900 by Mi&cher- 
lich. It is allowed that the combining measure of this vapour is l-3rd of a 
volume, which gives the theoretical density 6648. 

Sulphur and many other substances may be obtained in distinct crystals, 
on passing from a state of fusion, by operating in a particular manner. A 
considerable quantity of sulphur is fused in a stoneware crucible, and allowed 
to cool till it begins to solidify; the solid crust, with whieh its surface is co- 
vered, is then broken, and the portion remaining fluid poured out. On after- 
wards breaking the crucible, when it has become quite cold, the sulphur is 
found to have a considerable cavity which is lined with fine crystals, like a 
geode in quartz. Sulphur is dimorphous, the form which it assumes at a 
high temperature, and consequently in its passage from a state of fusion, is a 
secondary modification of an oblique prism with a rhomboidal base. Sulphur 
is also soluble in the sulphuret of carbon, the chloride of sulphur and oil of 
turpentine, and is deposited from solution in these menstrua at a lower tempe- 
rature, and of its second form, which is an elongated octohedron with a rhom- 
boidal base. That is likewise the form of the grains of flowers of sulphur, 
and of the fine transparent crystals of native sulphur, which are also formed 
by sublimation. 

Sulphur is not soluble in water or in alcohol. It combines readily with 
most metals, some of them, such as copper and silver in very thin plates, 
burning in its vapour, as iron does in oxygen gas. When iron and some 
other metals are mixed in a state of division with flowers of sulphur and heat 
applied, the sulphur first melts, and after a few seconds combination ensues 
with turgescence of the mass, which becomes red hot. Sulphur unites with 
bodies generally in the same multiple proportions as oxygen, and sometimes 
in additional proportions, particularly with potassium and the metals of the 

20* 



234 SULPHUR. 

alkalies and alkaline earths. When boiled with caustic potash or lime, red 
solutions are formed which contain a large quantity of sulphur, a considerable 
proportion of which is deposited as a white hydrate of sulphur, upon the ad- 
dition of an acid. With hydrogen, sulphur unites in single equivalents, and 
forms sulphuretted hydrogen gas, which is the analogue of water in the sul- 
phur series of compounds, and also another compound the persulphuret of 
hydrogen, which is deficient in stability, like the peroxide of hydrogen, and 
is decomposed or preserved by similar agencies. 

Sulphur is readily inflamed, taking fire below its boiling point and burning 
with a pale blue flame, and the formation of suffocating fumes, which are sul- 
phurous acid gas. It exhausts the oxygen of a confined portion of air by its 
combustion, more completely than carbonaceous combustibles, and on that ac- 
count, and partly also from a negative influence which sulphurous acid has 
upon the combustion of other bodies, it maybe employed in particular circum- 
stances to extinguish combustion; a handful of lump sulphur being dropt into 
a burning chimney as the most effectual means of extinguishing it. Sulphur 
unites directly with oxygen only in the proportions of sulphurous acid, but 
several compounds of the same elements may be formed which are all acids; 
namely 

Hyposulphurous acid S 2 2 

Sulphurous acid. ........ S0 2 

Hyposulphuric acid. . . . . . . . S 2 5 

Sulphuric acid S0 3 

Uses. — From its ready inflammability sulphur has long been applied to 
wood-matches. But its most considerable applications are in the composition of 
gunpowder and other deflagrating mixtures, and in the manufacture of sul- 
phuric acid, which there will again be occasion to notice in a more particular 
manner. 

SULPHUROUS ACID. 

Eq. 401.IT, or 32.12; S0 2 ; density 2210.6; combining measure^ []. 



Sulphurous acid was distinguished as a particular substance by Stahl, and 
first recognised as a gas by Dr. Priestley. It was subsequently analyzed 
with accuracy by Gay-Lussac and by Berzelius. 

Preparation. — When sulphur is burned in dry air or oxygen gas, sul- 
phurous acid is the sole product, and the gas is found to have undergone no 
change in volume. But sulphurous acid is more conveniently prepared by 
heating oil of vitriol upon mercury or copper, either of which becomes an ox- 
ide at the expense of one portion of the sulphuric acid, and thereby causes 
the formation of sulphurous acid. Charcoal, chips of wood, straw and such 
bodies occasion a similar decomposition of sulphuric acid, when heated with 
it, but the gas is then mixed with a large quantity of carbonic acid. If the 
sulphurous acid, however, is to be used to impregnate water, or in making 
alkaline sulphites, the presence of that gas is immaterial. With that object, a 
quantity of oil of vitriol, equal in volume to 4 ounce measures of water, 
which for brevity may be spoken of as 4 ounce measures of oil of vitriol, may 
be introduced into a flask (see fig. 78) with | ounce of pounded charcoal, and 
the two substances well mixed with agitation. Effervescence takes place, upon 
applying heat to the flask, from the evolution of gas, which may be conducted 
in the first instance into an intermediate phial, through the cork of which a 
stout tube passes, open at both ends and about 3-8ths of an inch in internal 



SULPHUROUS ACID. 



235 




diameter. This phial contains about an ounce of water, into which the tube 
dips, and serves the purpose of condensing any sulphuric acid vapour, that 
may be carried over by the gas, or of intercepting the p m 78< 

liquid material in the flask, if thrown out by ebulli- 
tion, and also of preventing the liquid in the second 
bottle from passing back, by the gas tube, into the 
generating flask, on the occurrence of a contraction of 
the air in that flask, by cooling or any other cause. 
When that contraction happens in this arrangement, 
the external air enters the intermediate phial by its 
open tube. The second bottle is nearly filled with 
the liquid to be impregnated by the gas. This is the 
form in most frequent use of the Wolfe's bottles, em- 
ployed in transmitting a stream of gas through a li- 
quid. 

Water at 60° is capable of dissolving 37 times its 
volume of sulphurous acid, which makes it necessary 
to collect this gas for examination in jars filled with 
mercury in the mercurial trough, and not over water. 
Its density is 2210.6, and it contains 2 volumes of oxygen with l-3rd of a 
volume of sulphur vapour, condensed into 2 volumes, which form its com- 
bining measure. It may eas'ily be obtained in the liquid state by transmitting 
the dry gas through a tube surrounded by a freezing mixture of ice and salt, 
and forms a colourless and very mobile liquid, of sp. gr. 1.45, which boils at 
14°. The volatility of this liquid is small at considerably lower temperatures, 
and it is not applicable with advantage to produce intense cold by its evapora- 
tion (Mr. Kemp.) With a little water, it forms a crystalline hydrate, which 
contains 20 per cent, of acid, and perhaps therefore 14 equivalents of water. 

Sulphurous acid is not decomposed by a high temperature; but several sub- 
stances such as carbon, hydrogen and potassium, which have a strong affinity 
for oxygen, decompose it at a red heat. This acid blanches many vegetable 
and animal colours, and the vapours of burning sulphur are therefore employed 
to whiten straw, and to bleach silk, to which they also impart a peculiar gloss. 
The colours are not destroyed, and may in general be restored by the application 
of a stronger acid or an alkali. Dry sulphurous acid exhibits no affinity for 
oxygen, but in contact with a little water, these gases slowly combine and 
sulphuric acid is formed. From the same affinity for oxygen, sulphurous acid 
deprives the solution of chameleon mineral of its red colour, and throws down 
iodine from iodic acid. It decomposes the solutions of those metals which have 
a weak affinity for oxygen, such as gold, silver and mercury (with heat,) and 
throws down these bodies in the metallic state. Sulphurous acid is conveniently 
withdrawn from a gaseous mixture by means of peroxide of lead, which is con- 
verted by absorbing this gas into the white sulphate of lead. By nitric acid, 
sulphurous acid is immediately converted into sulphuric acid. 

Sulphites. — The alkaline sulphites have a considerable resemblance to the 
corresponding sulphates. Their acid is precipitated by the chloride of barium, 
but the sulphite of barytes is dissolved by hydrochloric acid. Sulphurous acid 
is a weak acid and its salts are decomposed by most other acids. 

Uses. — Besides the application of which sulphurous acid is susceptible in 
bleaching, it is likewise employed in French hospitals, in the treatment of diseases 
of the skin. The gas is then applied in the form of a bath. (Dumas, Traite de 
Chimie appliquee aux Arts, t. 1, p. 151.) 

This oxide of sulphur, besides acting as an acid, appears to play the part of a 
radical, like carbonic oxide, and to pervade a class of compounds, in which hy- 
posulphurous acid and sulphuric acid are included. 



236 



SULPHUR, 



SULPHUROUS ACID SERIES. 

Sulphurous acid. 

Sulphuric acid. 

Hyposulphurous acid. 

Chlorosulphuric acid. 

Iodosulphuric acid. 

Nitrosulphuric acid. 

Crystals of the leaden chambers (de la Provostaye) 

Oxichloride of sulphur (H. Rose.) 



S0 2 

so 2 +o 

so 2 + s 

S0 2 -fCl 
S0 2 -fI 
S0 2 -fN0 2 
S0 2 +Cl-f-S0 2 
S0 2 -fCl + S0 2 



SULPHURIC ACID. 



Eq. 501.17, or 40.12; SO 3 ; density 2762; 



Chemists have been in possession of processes for preparing this acid since 
the end of the fifteenth century. It is of all reagents the one in most frequent 
use, being the key to the preparation of most of the other acids, which, in con- 
sequence of its superior affinities, it separates from their combinations, and 
being the acid preferred to others from its cheapness, for various useful and im- 
portant purposes in the arts. 

Preparation. — Sulphuric acid was first obtained by the distillation of green 
vitriol or copperas, a native sulphate of iron, and this process is still followed at 
Nordhausen in Saxony, for the preparation of a highly concentrated acid. The 
sulphate of iron contains seven equivalents of water, and is first dried, by which 
its water is reduced considerably below a single equivalent, and then distilled 
in a retort of stoneware at a red heat. When the experiment is performed on 
a small scale, the heat of an argand spirit lamp is sufficient : and in the place of 
copperas, the sulphate of iron previously peroxidized, the sulphate of bismuth, 
of antimony, or of mercury may be employed. The first effect of heat upon the 
dried copperas, is to cause an evolution of sulphurous acid gas, a portion of 
sulphuric acid being decomposed in converting the protoxide of iron of that salt 
into peroxide. Vapours afterwards come over, which condense into a fuming 
liquid, generally of a black colour, and of a density about 1.9, which is the 
Nordhausen acid, and contains less than one equivalent of water to two of 
sulphuric acid. This acid is preferred for dissolving indigo, and for some other 
purposes in the arts, and is the best source of anhydrous sulphuric acid. 

But sulphuric acid is prepared, in vastly greater quantity, by the oxidation 
of sulphur. When burned in air or oxygen, sulphur does not attain a higher 
degree of oxidation than sulphurous acid, but an additional proportion of 
oxygen may be communicated to it by two methods, and sulphuric acid 
formed. 

1°. When a mixture of sulphurous acid and air is made to pass over spongy 
platinum at a high temperature, the sulphurous acid is converted into sulphuric 
acid at the expense of the oxygen of the air. Mr. Peregrine Phillips, who 
first made this observation, has founded upon it a method of preparing sul- 
phuric acid on the large scale, which, although not yet sufficiently tried to es- 
tablish its advantage as a manufacturing process, is still of great interest in a 
scientific point of view, and deserves consideration. Sulphur is burned, or 
iron pyrites in place of it, and the sulphurous acid produced, is mixed with an 
excess of air, by a blowing apparatus, and carried through a tube filled with 
the platinum sponge or balls of fine platinum wire. The vapours of sulphuric 
acid formed, which are mixed with the nitrogen of the air, are condensed in a 



SULPHURIC ACID. 237 

long and narrow vessel of lead, in an upright position, filled with pebbles, 
which are kept constantly wet by a small stream of water, admitted at the top 
and which percolates downwards. 

2°. Sulphurous acid mixed with air may likewise be converted into sul- 
phuric acid, by the agency of nitric oxide, which is the process generally 
pursued in the manufacture of that acid. The theory of this latter method, 
which is by no means obvious, was established by the researches of Clement 
Desormes and of Sir H. Davy. When nitric oxide mixes with air in excess, 
it instantly combines with oxygen, and becomes in a great measure peroxide 
of nitrogen, or N0 4 . If dry sulphurous acid gas, S0 2 , be mixed with that 
compound, no change occurs, the two gases when dry having no action upon 
each other. But if a little moisture, in the state of vapour be admitted to the 
mixture, then oxygen is transferred from the peroxide of nitrogen to the sul- 
phurous acid, the former becoming nitrous acid N0 3 ; and the latter sulphuric 
acid S0 3 ; and these two acids, in combination with each other and with a por- 
tion of water, precipitate as a crystalline solid, a kind of sulphate of nitrous 
acid, of which the exact composition has been already given (page 215.) 
The effect of an additional small quantity of water upon this crystalline solid 
is remarkable, occasioning its decomposition with effervescence; a hydrate of 
sulphuric acid remains behind, and the nitrous acid is expelled in a state of 
decomposition, as nitric oxide and peroxide of nitrogen. The result then of 
these changes has been the formation of a certain quantity of sulphuric acid; 
and the nitric oxide is again restored to the gaseous atmosphere; where if it 
meets a second time with oxygen, sulphurous acid and moisture, it may give 
occasion to a repetition of the same changes, and the formation of an addi- 
tional proportion of sulphuric acid, and do so again and again, so long as it 
continues to meet with both oxygen, sulphurous acid, and moisture. The ni- 
tric oxide is thus a medium of transference, by which the oxygen of the air 
reaches the sulphurous acid, and a small portion of the former may be the 
means of converting a large quantity of the latter into sulphuric acid. 

In the manufacture upon the large scale, the sulphurous acid is converted 
into sulphuric acid, in oblong chambers of sheet-lead, supported by an external 
frame work of wood. Sulphurous acid from burning sulphur, nitric acid va- 
pour and steam are simultaneously admitted into the leaden chamber; and the 
sulphuric acid formed accumulates in the liquid state upon the floor of the 
chamber. The diagram below represents one of the most improved forms of 
the chamber, with its appendages. 

Fig. 79. 



a represents the water boiler, with its furnace for supplying the chamber 
with steam; b, the section of a small chamber in brickwork, or furnace, called 
the burner, upon the floor of which the sulphur burns, and in which there is a 
tripod supporting an iron capsule, which contains the materials for nitric acid, 
namely oil of vitriol and either nitre or nitrate of soda. The heat of the burn- 
ing sulphur evolves the nitric acid from these materials, and consequently the 
sulphurous acid becomes mixed with nitric acid vapour, which it carries for- 
ward with it, by a tube represented in the figure, into the chamber, where 
these acid vapours meet with the steam admitted near the same point, and the 
formation of sulphuric acid takes place. The nitric acid vapour is equivalent 



238 SULPHUR. 

to nitric oxide or peroxide of nitrogen, as the first effect of the sulphurous 
acid is to reduce the nitric acid to a lower state of oxidation. From 8 to 19 
parts of sulphur are consumed in the burner for 1 part of nitre decomposed 
there, so that the quantity of nitrous fumes is small compared with the quantity 
of sulphurous acid thrown into the chamber. The chamber itself is 72 feet 
in length by 14 in breadth and 10 in height, and is divided into three com- 
partments, by leaden curtains placed across it, two of which, d and/, are sus- 
pended from the roof, and reach to within six inches of the floor, and one e 
rises from the floor to within six inches of the roof, g is a leaden conduit 
tube, for the discharge of the uncondensible gases, which should communicate 
with a tall chimney, to carry off these gases and to occasion a slight draught 
through the chamber. The curtains serve to detain the vapours, and cause 
them to advance in a gradual manner through the chamber, so that the sulphuric 
acid is deposited as completely as possible, before the vapours reach the dis- 
charge tube. When the oxygen of the chamber is exhausted, the admission 
of acid vapours is discontinued, till the air in it is renewed. But the admission of 
air to the chamber is sometimes so regulated, that a continuous current is 
maintained through the chamber, and the combustion proceeds without inter- 
ruption. When steam is admitted in proper quantity, as in this method, it is 
not necessary to begin by covering the floor with water, as the sulphuric acid 
is condensed without it. 

The acid may be drawn off from the floor of the chamber of a sp. gr. as high 
as 1.6. It is further concentrated in open leaden pans, till it begins to act upon 
the metal and afterwards in retorts of platinum or glass. It still retains small 
quantities of nitrous acid and sulphate of lead, from which it can be completely 
purified by dilution with water and a second concentration. The acid thus 
obtained in its most concentrated state is a definite compound of one atom acid 
and one atom of water, which last cannot be separated by heat, the hydrate 
distilling over unchanged. It is the oil of vitriol of commerce. 

Properties.— Anhydrous sulphuric acid is obtained by gently heating the 
fuming acid of Nordhausen in a retort, and receiving its vopour in a bottle 
artificially cooled, which can afterwards be closed by a glass stopper. It con- 
denses in solid fibres, like asbestos, which are tenacious and may be moulded 
by the fingers like wax. Its density at 68° is 1.97. At 77° it is liquid, and a 
little above that temperature it enters into ebullition, affording a colourless vapour, 
which produces dense white fumes on mixing with air, by condensing the 
moisture in it. The dry acid does not redden litmus, an effect, which requires 
the presence of moisture. It combines with sulphur, and produces compounds 
which are of a brown, green and blue colour, and with one tenth of its weight 
of iodine forms a compound of a fine green colour, which assumes the crystal- 
line form. Heated in the acid vapour, caustic lime or barytes inflames and 
burns for a few seconds ; the vapour is absorbed, and sulphate of lime or barytes 
formed. The anhydrous acid has a great affinity for water, and when dropped 
into that liquid, occasions a burst of vapour, from the heat evolved. The density 
of its vapour was found to be 3000 by Mitscherlich, but it is probably 2762, 
and formed of 3 volumes of oxygen and l-3rd of a volume of sulphur vapour, 
condensed into 2 volumes, which constitute its combining measure. This 
vapour is resolved by a strong red heat into sulphurous acid and oxgen. 

When the Nordhausen acid is retained below 32°, well formed crystals appear 
in it, which Mitscherlich finds to be a compound of two equivalents of acid, and 
one of water, or 2S0 3 -fHO.* This compound is resolved by heat into the 
anhydrous acid, which sublimes, and the first hydrate, or oil of vitriol. 

The most concentrated oil of vitriol of the leaden chambers (HO-f S0 3 ) is a 

* Elemens de Chimie, par E. Mitscherlich, t. 2, p. 57. 



SULPHURIC ACID. 239 

dense, colourless fluid, of an oily consistence which boils at 620°, and freezes at 
— 29°, yielding often regular six-sided prisms of a tabular form. It has a 
specific gravity at 60° of 1.847 or a little higher, but never exceeding 1.850. 
It is a most powerful acid, supplanting all others from their combinations, with 
a few exceptions, and when undiluted is highly corrosive. It chars and destroys 
most organic substances. It has a strong sour taste, and reddens litmus even 
though greatly diluted. Sulphur is soluble to a small extent in the concentrated 
acid, and communicates a blue, green or brown tint to it ; so are selenium and 
tellurium. Charcoal also appears to be slightly soluble in this acid, imparting 
to it a pink tint, which afterwards becomes reddish brown. The concentrated 
acid has a great affinity for water, which it absorbs from the atmosphere ; and 
is usefully employed to dry substances placed near it in vacuo. Considerable heat 
is evolved in its combination with water ; when 4 parts by weight of the concen- 
trated acid were suddenly mixed with 1 part of water, the temperature was ob- 
served by Dr. Ure to rise to 300°. The density of this acid becomes less in 
proportion to its dilution. N 

Acid of sp. gr. 1.78 is a second hydrate, containing two atoms of water to 
one of acid. This hydrate forms large and regular crystals, even above the 
freezing point of water, and remains solid, according to Mr. Keir, till the tem- 
perature rises to 45°. If the dilute acid is evaporated at a heat not exceeding 
400° its water is reduced to the proportion of this hydrate. This second 
atom of water is expelled by a higher temperature, but the first atom can only 
be separated from the acid by a stronger base. Sulphuric acid forms still a 
third hydrate, of sp. gr. 1.632, containing three atoms of water, the proportion 
to which the water of a more dilute acid is reduced, by evaporation in vacuo 
at 212°. It is also in the proportions of this hydrate, that the acid and water 
undergo the greatest condensation, or reduction of volume, in combining. 
The following then are the formulae of the definite hydrates of this acid, in- 
cluding that derived by Mitscherlich from the Nordhausen acid: — 



HYDRATES OF SULPHURIC ACID. 

Hydrate in the Nordhausen acid - - HO,2S0 3 

Oil of vitriol (sp. gr. 1.850.) - - - HO, S0 3 

Acid of sp. gr. 1.78 HO, S0 3 -fHO 

Acid of sp. gr. 1.632 .... HO, S0 3 -f2HO 

Sulphuric acid acts in two different modes upon metals, dissolving some, 
such as copper and mercury, with the evolution of sulphurous acid, and others, 
such as zinc and iron, with the evolution of hydrogen gas. The metal is oxi- 
dated at the expense of the acid itself in the one case, and of the water in com- 
bination with the acid in the other. The acid acts with most advantage in the 
first mode, when concentrated, and in the second when considerably diluted. 

The presence of sulphuric acid in a liquid may always be detected by means 
of chloride of barium, which produces with this acid a white precipitate of 
sulphate of barytes, insoluble in both acids and alkalies. 

Sulphates. — Of no class of salts do chemists possess a more minute know- 
ledge than of the sulphates. The sulphates of zinc, magnesia, and other 
members of the magnesian family correspond closely with the hydrate of sul- 
phuric acid. Thus of the seven atoms of water which the crystallized sul- 
phate of magnesia possesses, it retains one at 400°, and is then analogous to 
the sulphate of water of sp. gr. 1.78; the formula of these two salts being, 

MgO, S0 3 +HO, 
HO, SO3 + HO, 



240 SULPHUR. 

and the atom of water in both salts may be replaced by sulphate of potash, 
when the sulphate of water forms the salt called the bisulphate of potash, and 
the sulphate of magnesia forms the double sulphate of magnesia and potash, 
of which the formulae also correspond: — 

HO, S0 3 +KO, SO, 
MgO, SO3 + KO, S0 3 . 

In all these sulphates, there is one atom of acid to one of base. But with 
potash, sulphuric acid forms a second salt, in which two of acid are combined 
with one of base, and which has lately been obtained in a crystallized state by 
M. Jacquelin.* The sulphates are known to correspond with the chromates, 
and this new salt corresponds with red chromate or bichromate of potash. A 
third sulphate of potash is to be looked for, corresponding with the terchro- 
mate of potash. The series of anhydrous sulphates of potash, admitting the 
latter, will therefore be 

Sulphate of potash KO + S0 3 KO+S0 3 K-fS0 4 

Bisulphate of potash KO-f2S0 3 KO + S 2 6 K+S 2 7 

Tersulphate of potash KO + 3S0 3 KO + S 3 9 K-j-S 3 O 10 

Sulphuric acid appears by the first column to be capable of combining with a 
base in three multiple proportions, and so also does chromic and probably also 
manganic and selenic acids which are isomorphous with sulphuric acid, while 
nitric acid and carbonic acid, so far as is known, combine with bases only in 
one proportion. Iodic acid, it will afterwards be found, corresponds with sul- 
phuric acid in this respect, there being an anhydrous iodate, biniodate and 
teriodate of soda (Mr. Penny.) The composition of such salts is not easily 
reconciled with the doctrine of the constitutional neutrality of salts, or with 
the salt-radical theory, as has already been remarked (page 139.) In the 
second column these sulphates are represented in a different manner, suggested 
by the relation in composition to each other of certain organic acids, particu- 
larly of the class including cyanic, fulminic and cyanuric acids, in the second 
and third of which, respectively, the atom of cyanogen is doubled and trebled. 
A similar duplication and triplication of the atom in compounds, seems to be 
not an uncommon cause of isomerism, as in the hydrocarburets (page 127, 
and table of densities, page 114.) The acid itself is supposed in the second 
column to be different in these three salts, namely, S0 3 , S 2 6 , S 3 9 ; and the 
salts cease to be anomalous, being all represented as neutral salts, containing 
one atom of acid, to one of base. In the third column, the same view of the 
constitution of these sulphates is accommodated to the salt radical theory. 

These duplicated and triplicated sulphuric acids are supposed above, to 
form each a monobasic class of sulphates; but if, moreover, it be assumed that 
one of them, the duplicated sulphuric acid S 2 6 , with the corresponding 
chromic acid Cr 2 6 , is also capable of forming a bibasic class of salts, then 
some other salts of the same class will be brought more in accordance with 
the general views entertained respecting salts, than those salts at present are, 
as their constitution is generally represented. The salts named will be re- 
presented as follows: 

Gypsum, or hydrated sulphate of lime 2CaO,S 2 6 +HO+3HO 

Johnston's hydrated sulphate of lime 2CaO,S 2 6 -f-HO 

NaO? 
Glauberite (sulphate of soda and lime) ^ q > -f S 2 6 

KO } 

Chromate of potash and soda N O C "^" ^ r 2^e 



* An. de Ch. et de Pa. t. 70, p. 311. 



HYPOSULPHUROUS ACID. 241 

Uses.— Sulphuric acid is employed to a large extent in eliminating nitric 
acid from nitrate of potash, and in the preparation of hydrochloric acid and 
chlorine, from chloride of sodium, and also in the processes of bleaching. 
But the greatest consumption of this acid is in the formation of sulphates, par- 
ticularly of sulphate of soda, by the decomposition of which salt, nearly all 
the carbonate of soda of commerce is at present procured. 



HYPOSULPHUROUS ACID. 
Eq. 602.34; S 2 2 or S0 2 +S; not isolable. 

The hyposulphites are better known than hyposulphurous acid itself, which 
is a body of little stability, quickly undergoing decomposition, when liberated 
by a stronger acid from a solution of any of its salts, and resolving itself into 
sulphurous acid, sulphuretted hydrogen and sulphur. These salts, long con- 
sidered as a species of double salts, and called sulphuretted sulphites, were 
first supposed to contain a peculiar acid by Dr. Thomson and by Gay-Lussac, 
a conjecture afterwards verified by Sir John Herschel, whose early researches 
upon this acid form the subject of a memoir of great interest.* 

Preparation. — The sulphite of soda, prepared by saturating a solution of 
carbonate of soda by sulphurous acid (page 234,) is converted into hyposul- 
phite, by digesting it upon flowers of sulphur at a high temperature, but with- 
out ebullition. The sulphurous acid assumes an atom of sulphur, and remains 
in combination with the soda; or, in symbols — 

NaO + S0 2 and S = NaO + S0 2 , S. 

The solution may afterwards be evaporated, (ebullition being always avoided, 
as the hyposulphites are all partially decomposed at 212°;) and affords large 
crystals of the hyposulphite of soda. When solution of caustic soda is di- 
gested upon sulphur, the latter is likewise dissolved, and a mixture of 1 eq. 
of hyposulphite of soda with 2 eq. of sulphuret of sodium results, of which 
the last may dissolve an excess of sulphur: — 

3NaO and 4S = NaO+ S,0 2 and 2 NaS. 

Exposed to the air, this solution slowly absorbs oxygen, and if it contains a 
certain excess of sulphur, passes entirely into hyposulphite of soda. 

The hyposulphite of lime is also formed, by digesting together one part of 
sulphur and 3 of hydrate of lime at a high temperature, when changes of the 
same nature occur as with sulphur and caustic soda, and the solution becomes 
red ; a stream of sulphurous acid gas is conducted through the solution after it 
has cooled, and converts the whole salt into hyposulphite, occasioning at the 
same time a considerable deposition of sulphur. The reaction here is rather 
complicated, the sulphurous acid uniting with one portion of sulphur, to form 
hyposulphurous acid, and also liberating another portion of the same element 
from the sulphuret of calcium. It is expressed in the following formula : 

2CaS and 3SO, = 2CaO + 2S 2 2 , and S. 

Zinc and iron also dissolve in the solution of sulphurous acid in water, with 
little or no effervescence, deriving the oxygen necessary to convert them into 
oxides, not from water, but from the sulphurous acid, two-thirds of which are 
thereby converted into hyposulphurous acid, which combines with half of the 
oxide produced ; while the other third, remaining as sulphurous acid, unites with 
the other moiety of the same oxide : — 

* Edinburgh Philosophical Journal, Vol. I. pp. 8 and 396. 
21 



242 SULPHAS. 

3S0 3 and 2Zn = ZnO, S 2 2 and ZNO, S0 2 . 
The hyposulphite obtained by this process is, therefore, mixed with a sulphite. 

Properties. — The acid of these salts undergoes decomposition when they are 
strongly heated, or treated with an acid. It forms soluble salts with lime and 
strontian, in which respect it differs from sulphurous and sulphuric acids ; the 
hyposulphite of barytes is insoluble. It also forms a remarkable salt with silver, 
which has no metallic flavour, but tastes extremely sweet. The existence of a 
hyposulphite in a solution, is easily recognised, by its possessing the power to 
dissolve freshly precipitated chloride of silver, and become sweet. 

Uses. — The hyposulphite of soda is employed to distinguish between the 
earths strontian and barytes, the latter of which it precipitates, and not the 
former. It is also applied, in certain circumstances, to dissolve the insoluble salts 
of silver. 

CHLOROSULPHURIC ACID. 
Eq. 843.8 or 67,6; SO,Cl; 4652; r~T~|. 



A compound which contains sulphur, oxygen, and chlorine, has lately been 
discovered by M. Regnault, which he considers as a combination of sulphurous 
acid with chlorine, and therefore a member of the sulphurous acid series * The 
circumstances of the formation of this compound are singular. Chlorine and 
sulphurous acid gases, dry or humid, may be mixed and even transmitted 
through a glass tube, containing pounded glass or spongy platinum, at all tem- 
peratures, without combining. But when chlorine, which should be perfectly 
dry, is allowed to meet in a glass balloon at once sulphurous acid and olefiant gas, 
perfectly dry, a chloride of sulphurous acid, and a chloride of olefiant gas are si- 
multaneously formed, with the evolution of much heat, and condense together as 
an extremely mobile liquid, of a sharp and suffocating odour. Regnault has ob- 
served that neither of these compounds can be produced without the other, 
although they are produced in a variable relation to each other as to quantity. 
The olefiant gas, evolved upon heating 6 parts of oil of vitriol with 1 part of con- 
centrated alcohol, passed through two vessels containing oil of vitriol, to dry it, 
contains enough of sulphurous acid for the preceding experiment. The liquor 
produced, thrown into water, falls first to the bottom, in the form of oily drops, 
but soon dissolves partially with elevation of temperature, and the chloride of 
olefiant gas separates unaltered. The chlorosulphuric acid itself, in dissolving, 
decomposes 1 atom of water, and changes into hydrochloric acid and sulphuric 
acid, a reaction which demonstrates the original compound to consist of 1 
atom of sulphurous acid with 1 atom of chlorine. 

The density of the vapour of chlorosulphuric acid, was found by experiment 
to be 4703, which agrees with the theoretical density 4652. It consists of 2 
volumes of sulphurous acid and 2 volumes of chlorine condensed into 2 volumes, 
which form the combining measure of the vapour. In its condensation, it re- 
sembles the vapour of anhydrous sulphuric acid. This body also corresponds 
exactly in composition with the compound hitherto called chlorochromic acid, 
of which the true formula is Cr0 2 Cl, chromium being substituted in the latter 
for the sulphur of the former. 

With dry ammoniacal gas, chlorosulphuric acid forms a white powder, which 
is a mixture of the hydrochlorate of ammonia (sal ammoniac) and the true 
sulphamide, S0 2 +NH 2 . It does not combine, as an acid, with bases. 

Mr. Lyon Playfair has also lately formed a corresponding zWosulphuric acid, 

* An. de Ch. et de Ph. t. 69, p. 170. 



NITROSULPHURIC ACID. 243 

by distilling 2 equivalents of iodine with 1 eq. of sulphite of lead, and by trans- 
mitting sulphurous acid through a solution of iodine in wood-spirit, in which 
this compound is soluble. It is a dense liquid, decomposed by water. Mr. 
Playfair is likely to add other acids to this class. 



NITROSULPHURIC ACID. 

Eq. 778.2 or 62.3; SN0 4 or S0 2 , N0 2 ; not isolable. 

Sir H. Davy made the observation that nitric oxide is absorbed by a mixture 
of sulphite of soda and caustic soda, and that a compound is produced, of which 
the principal characteristic is to disengage abundance of nitrous oxide, upon the 
addition of an acid to it. He , concluded that the nitrous oxide, which then 
escapes, was previously united with soda, and gave this as an instance of the 
combination of that neutral oxide with an alkali. As the sulphite of soda be- 
came at the same time sulphate, the conversion of the nitric oxide into nitrous 
oxide appeared to be explained. It has, however, been lately proved by Pelouze, 
that a new acid is formed in the circumstances of the experiment, to which he 
has given the name nitrosulphuric, and which may be considered a compound 
of sulphurous acid and nitric oxide, or another member of the sulphurous acid 
series.* 

Preparation. — If a mixture be made over mercury of 2 volumes of sulphurous 
acid, and 4 volumes of nitric oxide, which are combining measures of these 
gases, no change occurs: but on throwing up a strong solution of caustic pot- 
ash into the gases, they disappear entirely after some hours, combining with a 
single equivalent of potash, and forming together the nitrosulphate of potash. 
But it is better to prepare the nitrosulphate of ammonia. A concentrated solution 
is made of sulphite of ammonia, which is mixed with 5 or 6 times its volume of 
solution of ammonia, and into this, nitric oxide is passed for several hours. A 
number of beautiful crystals are gradually deposited : they are to be washed 
with a solution of ammonia previously cooled, which besides the advantage of 
retarding their decomposition, offers that of dissolving less of them than pure 
water. When the crystals are desiccated, they should be introduced into a well 
closed bottle; in this state they undergo no alteration. The same process is 
applicable to the corresponding salts of potash and soda. When a strong acid 
is added to a solution of these salts, for the purpose of isolating the nitrosulphuric 
acid, the latter on being set free, decomposes spontaneously into sulphuric acid 
and nitrous oxide, which comes off with effervescence. 

Properties. — The acid of the nitrosulphates is not precipitated by barytes. 
The nitrosulphate of potash, when heated, becomes sulphite, and evolves nitric 
oxide; but the salts of soda and ammonia become sulphates, and evolve nitrous 
oxide. No nitrosulphates of the metallic oxides which are insoluble in water, 
have been formed, or appear capable of existing ; for when such salts as chloride 
of mercury, the sulphate of zinc or of copper, the persulphate of iron and the 
nitrate of silver are added to the nitrosulphate of ammonia, they produce a brisk 
effervescence of nitrous oxide, with the formation of sulphate of ammonia, or they 
decompose the nitrosulphate of ammonia as free acids do. Indeed the only 
nitrosulphates which have been formed are those of potash, soda and ammonia. 
These are neutral, and have a sharp and slightly bitter taste, with nothing of 
that of the sulphites. 

These salts vie with the peroxide of hydrogen in facility of decomposition. 
The nitrosulphate of ammonia resists 230°, but is decomposed with explosion a 

* Pelouze in Taylor's Scientific Memoirs, vol. 1, p. 470; or An. de Ch. et de Ph. t. 60, p. 151, 



244 



SULPHUR. 



few degrees above that temperature, caused by the rapid disengagement of 
nitrous oxide. Solutions of the nitrosulphates are not stable above the freezing 
point, but their stability is much increased by an excess of alkali. They are re- 
solved into sulphate and nitrous oxide, by the mere contact of certain substances, 
which do not themselves undergo any change, such as spongy platinum, silver 
and its oxide, charcoal powder and peroxide of manganese, by acids, even car- 
bonic acid, and by metallic salts. 



HYPOSULPHURIC ACID. 

^.902.3 or 72.24; S 2 5 ; not isolable. 

Preparation. — This acid of sulphur was discovered by Gay-Lussac and 
Welter, in 1819. To prepare it, a quantity of peroxide of manganese, which 
must not be hydrated, is reduced to an extremely fine powder, suspended by 
agitation in water, and sulphurous acid gas is transmitted through the water. 
The temperature is apt to rise during the absorption of the gas, but must be 
repressed, otherwise much sulphuric acid is produced, the formation of which, 
indeed, it is impossible to prevent entirely, but of which the quantity is re- 
duced almost to nothing, when the liquor is kept cold during the operation. 
The peroxide of manganese disappears, and a solution of hyposulphate of the 
protoxide of manganese is formed; 2 equivalents of sulphurous acid, and 1 of 
peroxide of manganese, forming one of hyposulphuric acid and one of pro- 
toxide of manganese, or 

2S0 2 and Mn0 2 = MnO + S 2 5 . 

The solution is filtered, and then mixed with a solution of sulphuret of barium, 
which occasions the precipitation of the insoluble sulphuret of manganese, 
with the transference of the hyposulphuric acid to barytes. From this hypo- 
sulphate of barytes, the hyposulphates of other metallic oxides may be pre- 
pared, by adding their sulphates to that salt, when the insoluble sulphate of 
barytes will precipitate, and the hyposulphate of the metallic oxide added 
remain in solution. But to procure the hyposulphuric acid itself, the solution 
of hyposulphate of barytes may be evaporated to dryness, and being perfectly 
pure, it is reduced to a fine powder, weighed and dissolved in water; for 100 
parts of it 18.78 parts of oil of vitriol are taken, which after dilution with 3 or 
4 times as much water, are employed to decompose the salt of barytes. The 
liberated hyposulphuric acid solution is filtered, and evaporated in vacuo over 
sulphuric acid, till it attains a density of 1.347, which must not be exceeded, 
as the acid solution begins then to decompose spontaneously into sulphurous 
acid, which escapes, and sulphuric acid which remains in the liquor. 

Properties. — This acid has not been obtained in the anhydrous condition. 
Its aqueous solution has no great stability, being decomposed at its tempera- 
ture of ebullition. The same solution exposed to air in the cold slowly ab- 
sorbs oxygen, according to Heeren, and becomes sulphuric acid. But neither 
nitric acid, nor chlorine, nor peroxide of manganese oxidize this acid, unless 
they are boiled in its solution. Its salts are perfectly stable, either when in 
solution, or when dry, and are in general very soluble, having some analogy 
to the nitrates. A hyposulphate, when heated to redness, leaves a neutral 
sulphate, and allows a quantity of sulphurous acid to escape, which would be 
sufficient to form a neutral sulphite with the base of the sulphate. This class 
of salts was particularly examined by Heeren.* Hyposulphuric acid is ima- 

* PoggendorfTs Annalen, v. vii, p. 77, 



SELENIUM. 245 

gined to exist in acid compounds produced by the action of sulphuric acid on 
some principles of organic chemistry, in the sulpho-napthalic acid, for in- 
stance. 

SECTION VIII. 

SELENIUM. 

Eq. 494.58 or 39.63; Se; density of vapour unknown. 

This element was discovered by Berzelius in 1817, in the sulphur of Fah- 
lun, employed in a sulphuric acid manufactory in Sweden, and was named by 
him selenium, from SeAsjvjj, the moon, on account of its strong analogy to ano- 
ther element tellurium, which derives its name from tellus, the earth. It is 
one of the least abundant of the elements, but is found in minute quantity in 
several ores of copper, silver, lead, bismuth, tellurium and gold in Sweden 
and Norway; and in combination with lead, silver, copper and mercury in the 
Hartz. It is extracted from a seleniferous ore of silver of a mine in the latter 
district, and supplied for sale in little cylinders of the thickness of a goose- 
quill, and three inches in length; or in the form of small medallions of its dis- 
coverer. It has also been found in the Lipari islands in combination with 
sulphur, and can sometimes be detected in the sulphuric acid, both of Ger- 
many and England. It is separated from its combinations with sulphur and 
metals by a very complicated process, for which I must refer to the works of 
Berzelius.* 

Properties of selenium. — This element is allied to sulphur, and like that 
body, exhibits considerable variety in its physical characters. When it cools 
after being distilled, its surface reflects light like a mirror, has a deep reddish 
brown colour, with a metallic lustre resembling that of polished blood-stone. 
Its density is between 4.3 and 4.32. When cooled slowly after fusion, its 
surface is rough, of a leaden gray colour, its fracture fine-grained, and the 
mass resembles exactly a fragment of cobalt. But as selenium does not con- 
duct electricity, and its metallic characters are not constant, it is better classed 
with the non-metallic bodies. Its powder is of a deep red colour. By heat 
it is softened, becoming semifluid at 212°, and fusing completely a few degrees 
higher. It remains a long time soft on cooling, and may then be drawn out 
like sealing wax into thin and very flexible threads, which are gray and ex- 
hibit a metallic lustre by reflected light, but are transparent and of a ruby red 
colour by transmitted light. It boils about 650°, and gives a vapour of a yel- 
low colour, less intense than that of sulphur, but more so than that of chlorine. 
The density of this vapour has not been ascertained. 

Selenium combines in three proportions with oxygen, forming selenic acid, 
which corresponds with sulphuric acid, selenious acid corresponding with 
sulphurous acid, and a protoxide, to which there is no oxide of sulphur ana- 
logous. 

Oxide of selenium, SeO. — This is a colourless gas, sparingly soluble in 
water, formed when selenium is heated in air without burning freely. It has 
a powerful odour, suggesting that of decaying horse-radish, by means of which 
the smallest trace of selenium may be detected in minerals, when heated be- 
fore the blow-pipe, this gas being then formed. 

Selenious acid, SeO z .— Selenium strongly heated in a glass bulb, with a 
current of oxygen passing over it, takes fire and burns with a flame, white at 

* Annals of Philosophy, vol. 13, p. 401 ; or An.de Ch. et de Phys. t.9, p. 160; also Ber- 
zelius's Traite, t. 1, p. 334, BrusseU's edition, 1833. 

21* 



246 PHOSPHORUS. 

the base, and of a bluish green at the point and edges, but not strongly lumi- 
nous; selenious acid at the same time condenses as a white sublimate, in long 
quadrilateral needles. Its vapour has the colour of chlorine. The same acid 
is the sole product of the action of nitric or nitro-muriatic acid upon selenium, 
and is obtained on slowly cooling the liquor, in large prismatic crystals, 
striated lengthwise, which have a considerable resemblance to nitre. These 
crystals are hydrated selenious acid. This acid is largely soluble, both in 
water and alcohol. It is decomposed when in solution and selenium precipi- 
tated by zinc, iron or sulphite of ammonia, with the assistance of a free acid. 
The selenite of ammonia is also decomposed by heat and leaves selenium. 
The selenious is a strong acid, displacing nitric and hydrochloric acids from 
their combinations, but is displaced in its turn by the more fixed acids, sul- 
phuric, boracic, &c. 

Selenic acid, Se0 3 . — Selenium is brought to this superior state of oxidation 
at a high temperature, by fusion with nitre, a process which affords the sele- 
niate of potash. The selenic acid is precipitated from that salt by the nitrate 
of lead; and the insoluble seleniate of lead, after being washed, is diffused 
through water and decomposed by a stream of sulphuretted hydrogen gas, 
which converts the lead into insoluble sulphuret of lead and liberates selenic 
acid. A solution of this acid may be concentrated till its boiling point rises 
to 536°, but above that temperature it changes rapidly into selenious acid, 
with disengagement of oxygen. Its density is then 2.60, and it contains little 
more than a single equivalent of water, and therefore corresponds with the 
protohydrate of sulphuric acid, or oil of vitriol. Selenic acid has never been 
obtained in the anhydrous condition. Zinc and iron are dissolved by this 
acid, with the evolution of hydrogen gas; and with the aid of heat it dissolves 
copper and even gold, an operation in which it is partially converted into se- 
lenious acid. But it does not dissolve platinum. To precipitate its selenium, 
the acid may be digested with hydrochloric acid, which occasions the forma- 
tion of selenious acid and the evolution of chlorine, and then sulphurous acid 
throws down the selenium. The compounds of selenic acid with bases, so 
much resemble the corresponding sulphates, in their crystalline form, colour 
and external characters, that they can only be distinguished from them by the 
property which the seleniates have of detonating when ignited with charcoal, 
and causing a disengagement of chlorine when heated with hydrochloric acid. 
To separate the selenic from the sulphuric acid, Berzelius recommends the 
saturation of the acids with potash, and the ignition of the dried salt, mixed 
with sal-ammoniac; the selenic acid is decomposed by the ammonia and re- 
duced to the state of selenium. 



SECTION XL 

PHOSPHORUS. 

Eq. 392.28 or 31.44 (196.14 or 15.72 according to Berzelius and Turner;) 
P; density of vapour 4325; | I . 

This remarkable element appears to be essential to the organization of the 
higher animals, being found in their fluids, and forming in the state of phos- 
phate of lime, the basis of the solid structure of the bones. It is also found 
in most plants, and in a few minerals. Phosphorus was first obtained by 
Brand of Hamburgh in 1660, but Kunkel first made public a process for pre- 
paring it, which was afterwards improved by Margraff and by Scheele. Its 



PROPERTIES. 247 

ready inflammability, from which phosphorus derived its name, has always 
made this substance an object of popular interest; while the singularity, im- 
portance and variety of the phosphoric compounds have drawn to them no or- 
dinary share of the attention of chemists. 

Preparation. — Phosphorus is not a substance that can be easily prepared on 
a small scale, but ever since the time of Godfrey Hankwitz, to whom Mr. 
Boyle communicated a process for preparing it, phosphorus has been manu- 
factured in London, in considerable quantity and of great purity, for the use 
of chemists. The earth of bones is decomposed by 2-3rds of its weight of 
sulphuric acid, and the insoluble sulphate of lime separated by filtration from 
the soluble phosphoric acid, which passes through with a quantity of phos- 
phate of lime in solution. The acid liquor is then evaporated to the consis- 
tence of a syrup, and mixed with charcoal to form a soft paste, which is 
rubbed well in a mortar, and then dried in an iron pot with constant stirring 
till the mass begins to be red hot. It is allowed to cool, and introduced as 
rapidly as possible into a stoneware retort, previously covered with a coating 
of fire clay. The beak of the retort is inserted into a wider copper tube of a 
few feet in length, the free end of which is bent downwards a few inches from 
its extremity; and the descending portion introduced into a wide-mouthed bottle, 
containing enough of water to cover the extremity of the tube to the extent of 
t line or two. The heat of the furnace in which the retort is placed, is slowly 
laised for three or four hours, and then urged vigorously till phosphorus ceases 
t» drop into the water from the copper tube, which may continue from fifteen 
tc thirty hours, according to the size of the retort. Carbon at a high tempera- 
tire takes oxygen from the phosphoric acid, and becomes carbonic oxide, so 
that the phosphorus is all along accompanied by that gas. 

Vohler recommends, instead of the preceding process, to calcine ivory 
blaci, which is a mixture of phosphate of lime and charcoal, with fine quartzy 
sand and a little more ordinary charcoal, in cylinders of fire clay, at a very 
high temperature. Each cylinder has a bent copper tube adapted to it, one 
branch of which descends into a vessel containing water. The efficiency of 
Wohler's process depends upon the silica acting as an acid, and combining 
with the lime of the phosphate, at a high temperature, while the liberated phos- 
phoric acid is decomposed by the carbon. 

Properties. — At the usual temperature phosphorus is a translucent soft solid 
of a light amber colour, which may be bent or cut with a knife, and the cut 
surface has a waxy lustre. Its density is 1.77. Phosphorus melts at 108°, 
undergoing a remarkable dilatation of 0.0314 of its volume and becoming 
transparent and colourless immediately before fusion. It forms a transparent 
liquid, possessing like most combustible bodies, a high refracting power. 
At 217° it begins to emit a slight vapour, and boils at 550°, being con- 
verted into a vapour which is colourless, of sp. gr. 4355, according to the 
experiment of Dumas, which coincides almost with the theoretical density 
4325. Its combining measure, like that of oxygen, is 1 volume, allowing its 
equivalent to be 392. When fused and left undisturbed, it sometimes remains 
liquid for hours at the usual temperature, particularly when covered by an al- 
kaline liquid, but becomes solid when touched. Thenard has observed that 
when cooled very suddenly, as by throwing it melted into ice-cold water, it 
becomes absolutely black. Light causes it, in all circumstances, to assume a 
red tint; to avoid which action phosphorus is usually preserved in an opaque 
bottle. From its solution in hot naphtha it may be obtained, in cooling, in re- 
gular dodekahedral crystals. It is quite insoluble in water, but soluble to a 
small extent, with the aid of heat, in fixed and volatile oils, in sulphuret of 
carbon, of which 100 parts dissolve 20 of phosphorus, in chloride of sulphur, 
sulphuret of phosphorus, and ether. 

Phosphorus undergoes oxidation in the open air, and diffuses white vapours. 



248 PHOSPHORUS. 

which have a peculiar odour, suggesting to some that of garlic, and are lu- 
minous in the dark; and at the same time the phosphorus becomes covered 
with acid drops, which arise from the phosphorus acid, produced in these cir- 
cumstances, attracting the humidity of the air. This slow combustion is at- 
tended with a sensible evolution of heat, and may terminate in the fusion of 
the phosphorus, and its inflammation with combustion at a high temperature. 
There is a necessity for caution, therefore, in handling phosphorus, a burn from 
this body in a state of ignition being in general exceedingly severe. It is 
preserved under the surface of water. The low combustion of phosphorus 
has been particularly studied. It is not observed a few degrees below 32 c , 
but is sensible at that temperature, and increases perceptibly a few degrees 
above it. The presence of certain gaseous substances, even in minute quan- 
tity, has a remarkable effect in preventing the slow combustion of phosphorus; 
thus at 66°, it is entirely prevented by the presence, 

Volumes of air. 

of 1 volume of olefiant gas in 450 

of 1 volume of vapour of sulphuric ether in . .150 

of 1 volume of vapour of naphtha in . . . . 1820 
of 1 volume of vapour of oil of turpentine in . . 4444 

and the influence of these gases or vapours is not confined to low temperatures, 
a certain admixture of all of them defending phosphorus from oxidation ever 
at 200°. But on allowing such a gaseous mixture to expand, by diminishing 
the pressure upon it to a half or a tenth, the phosphorus becomes luminou?, 
and the proportion of foreign gas required to prevent the slow combustion 
must be greatly increased. The only explanation of this phenomenon, whbh 
can be offered at present, is that the gases \v T hich exert this influence have an 
attraction for oxygen, and there is reason to believe are themselves undergoing 
a slow oxidation at the same time. Now when two oxidable bodies art in 
contact, one of them often takes precedence in combining with oxygen, to the 
entire exclusion of the other. Potassium is defended from oxidation in air, 
by the same vapours, although to a less degree .* It is curious that in pure 
oxygen, phosphorus may remain without oxidating at all, at temperatures be- 
low, 60°, but an inconsiderable rarefaction of the gas, from diminution of the 
pressure upon it, will cause the phosphorus to burst into the luminous condi- 
tion. The dilution of the oxygen with nitrogen, hydrogen or carbonic acid 
produces the same effect. When gradually heated in air, phosphorus generally 
catches fire, and begins to undergo the high combustion, before its temperature 
has risen to 140°; of this high combustion, the sole product is phosphoric 
acid. 

- Phosphorus is susceptible of four different degrees of oxidation, the highest 
of which is a powerful acid, while the acid character is not absent even in the 
lowest. These compounds are: 

Oxide of phosphorus 2P+0 

Hypophosphorous acid . . . . . . P4-0 

Phosphorous acid ... ... P+30 

Phosphoric acid ... ... P-f50 



OXIDE OF PHOSPHORUS. 

Eq. 884.56 or 70.88, P 2 0. 
When burned in air or oxygen, phosphorus generally leaves behind it a 
* Quarterly Journal of Science, N. S. vol. vi. p. 83. 



HYPOPHOSPHOROUS ACID. 249 

small quantity of a red matter, which is an oxide of phosphorus. The same 
compound is obtained, in larger quantity, by directing a stream of oxygen gas, 
upon melted phosphorus, under hot water, and was found by Pelouze to con- 
tain 3 equivalents of phosphorus to 2 of oxygen.* 

But this oxide is impure, and the definite oxide appears to have been first 
obtained by Leverrier, who has carefully examined itt His process is to ex- 
pose to the air small fragments of phosphorus covered by the liquid chloride 
of phosphorus (P Cl 3 ,) in an open bolt-head. Phosphoric acid is formed, and 
also a yellow matter, which he finds to be a phosphate of the oxide of phos- 
phorus, and which gives a yellow solution with water. This solution is de- 
composed about 176°, and a flocculent yellow matter subsides, which is a hy- 
drate of the oxide of phosphorus, nearly insoluble in water. This compound 
abandons its combined water, when dried in vacuo over sulphuric acid, or when 
cooled below 32°, when the water separates as ice, and oxide of phosphorus 
remains perfectly pure. 

The oxide of phosphorus is a powder of a canary yellow colour, denser 
than water, and soluble neither in water, alcohol, nor ether. It may be kept 
in dry air without change. It resists a temperature of 570° without decom- 
position, but assumes a lively red colour; and does not take fire in air till heated 
a little above the boiling point of mercury. This oxide absorbs dry aramo- 
niacal gas, and appears to form feeble combinations with the fixed alkalies. 
Leverrier assigns to its hydrate the composition P o 0+2H0, and its phosphate, 
2P 2 0+3P0 5 . 



HYPOPHOSPHOROUS ACID. 

Eq. 492.28 or 39.44; PO; not isolable. 

This acid was discovered in 1816 by Dulong.J It was obtained by the ac- 
tion of water upon the phosphuret of barium, of which the phosphorus of 
one portion oxidates and becomes the acid in question, at the expense of the 
water, while the phosphorus of another portion, combining with the hydrogen 
of the water, produces phosphuretted hydrogen gas. Rose prepares the same 
hypophosphite of barytes, by boiling phosphorus and caustic barytes together, 
till all the phosphorus disappears and the vapours have no longer the smell of 
garlic.§ This solution is filtered, and to separate the hyphosphorous acid from 
barytes, diluted sulphuric acid is added which precipitates the latter. The 
acid remaining in solution may be concentrated with caution, to the consistence 
of a thick syrup, but affords no crystals. More strongly heated, this hydrate 
of hypophosphorous acid undergoes decomposition, being converted into 
phosphoric acid, with the evolution of phosphuretted hydrogen and a deposi- 
tion of phosphorus (Dulong.) 

The hypophosphites are all soluble in water, and like the salts of the mag- 
nesian family, such as those of magnesia and cobalt, easily crystallized. The 
dry salts are permanent in the air, but their solutions evaporated by heat, absorb 
oxygen. They contain l£ equivalents of water, which are essential to their 
constitution (Rose.) 

Considering the disposition of the acids of phosphorus to be bibasic and 
tribasic, it is not impossible that the real equivalent of this acid may be either 

* An. de Ch. et de Ph. t. 50, p. 83. 

t An. de Ch. et de Ph. t. 65, p. 257. 

* An. de Ch. et de Ph. t. 2, p. 141. 

§ H. Rose, sur les Hypophosphites, An. de Ch. et de Ph. t. 38, p. 258. 



250 PHOSPHORUS. 

2P+20, like hyposulphurous acid, or 3P-f 30, instead of PO. The subject 
requires farther investigation. 



PHOSPHOROUS ACID. 
Eq. 692.28, or 55.44; P0 3 . 

Preparation. — This acid is the principal product of the slow combustion of 
phosphorus, but changes after its formation into phosphoric acid, from the ab- 
sorption of oxygen. It may be obtained in the anhydrous condition by burn- 
ing phosphorus with imperfect access of air. Berzelius recommends for this 
operation a tube of glass, about 10 inches in length and I inch in diameter, 
which is nearly closed at one end, an opening no greater than a large pin hole 
being left there, and at a distance of an inch from this extremity the tube is 
bent at an obtuse angle. A small fragment of phosphorus is introduced into 
the angle of the tube, and heated till it takes fire. It burns with a pale green- 
ish flame, and the phosphorous acid produced is carried along by the feeble 
current of air. and condenses in the ascending part of the tube, as a white 
powder, not in the slightest degree crystalline. The phosphorus must not be 
so much heated as to cause it to sublime unchanged. In contact with air, 
phosphorous acid is apt to inflame, from the heat occasioned by the condensa-" 
tion of moisture, and is converted into phosphoric acid. The phosphorous 
acid itself is immediately soluble in water, while the phosphoric acid, which it 
sometimes contains, remains for a short time undissolved, in the form of white 
translucent flocks. 

Hydrated phosphorous acid, which is the source of pure phosphuretted hy- 
drogen gas, cannot be obtained without some trouble. When a few drops of 
water are thrown on the chloride of phosphorus (PC1 3 ) that compound evolves 
hydrochloric acid gas, and gives hydrated phosphorous acid. But it is more 
conveniently obtained by the method of Droquet. Two or three ounces of 
phosphorus are melted in a cylindrical glass receiver or sealed tube, of 8 or 
10 inches in length and nearly an inch in diameter, and the tube nearly filled 
with water. This tube, which will contain a column of fluid phosphorus of 
5 or 6 inches in height is then properly disposed in a basin or bolt-head of 
warm water, so as to retain the phosphorus fluid. Chlorine gas is conveyed 
by a quill tube, from the flask in which it is generated, to the bottom of the 
fluid phosphorus, where combination takes place with ignition, and the chlo- 
ride of phosphorus is formed. This chloride is dissolved by the water cover- 
ing the phosphorus, and converted into hydrochloric acid and phosphorous 
acid. The chlorine must be transmitted very slowly through the phosphorus, 
as any portion of that gas which reaches the water, converts the phosphorous 
into phosphoric acid; and the absorption of the chlorine by the phosphorus is 
most complete, when it is free from any other gas. When the remaining 
phosphorus fixes, upon cooling, the acid fluid may be poured off, and concen- 
trated by boiling, till it becomes sirupy and the volatile hydrochloric acid is 
entirely expelled. Phosphuretted hydrogen may also be obtained from the" 
iodide of phosphorus, which is more easily prepared. 

Properties. — In its most concentrated state, the hydrate of phosphorous 
acid contains three equivalents of water, its formula being 3HO+P0 3 ; and 
when heated it is resolved into hydrated phosphoric acid, and pure phosphu- 
retted hydrogen gas, which is not spontaneously inflammable. The solution 
of phosphorous acid absorbs oxygen from the air, slowly, if concentrated, but 
quickly when dilute. Like sulphurous acid, it takes oxygen from the salts of 



PHOSPHORIC ACID. 251 

mercury and the less oxidable metals, and precipitates the latter, particularly 
when aided by heat. It is one of the feeblest acids known. 

Phosphites,— The class of phosphites, which has been examined is certainly 
tribasic, that is, they contain 3 atoms of base to 1 of phosphorous acid. The 
hydrated acid is the tribasic phosphite of water. All our information respect- 
ing them is contained in the papers of Berzelius.* 



PHOSPHORIC ACID. 

Eq. 892.28, or 71.44; P0 5 ; forms three hydrates and three classes of 

Its: 

Monobasic phosphate of water, or metaphosphate of water HO-f-P0 5 

Bibasic phosphate of water, or pyrophosphate of water . 2HO-fP0 5 

Tribasic phosphate of water, or phosphate of water . 3HO+P0 5 

Preparation. — To obtain this acid in a state of purity, the most convenient 
process is to set fire to about a drachm of phosphorus upon a little metallic 
capsule, placed in the centre of a large stone-ware plate, and immediately 
cover it by a dry bell jar of the largest size. The phosphorous is converted 
into white flakes of phosphoric acid which are retained, with very little loss, 
within the bell-jar, and fall upon the plate like snow. The dry phosphoric 
acid is distinguished by the same shade of white, absence of crystallization, 
and perfect opacity, as solid carbonic acid. Exposed for a few minutes to the 
air, it deliquesces; and when the solid acid is collected in a wine-glass, and 
a few drops of water are thrown upon it, it is converted into a hydrate with 
explosive ebullition, from the heat evolved. The anhydrous acid is perfectly 
fixed, unless in the presence of aqueous vapour, when it sublimes away, pro- 
bably in the state of a hydrate. 

Phosphorus may likewise be oxidated by means of nitric acid. In this ope- 
ration, the fuming nitric acid should be diluted with an equal bulk of water, 
to avoid accidents from the violent action of the acid, which may cause the 
phosphorus to be projected in a state of ignition; the diluted acid is boiled upon 
the phosphorus, and being afterwards evaporated to dryness, it yields a hy- 
drated phosphoric acid. 

Phosphoric acid is also obtained in large quantity from calcined bones, 
which are reduced to a fine powder and mixed with 4-5ths of their weight of 
oil of vitriol, previously diluted with 4 or 5 times its bulk of water, as in the 
preparation of phosphorus (page 247.) Carbonate of ammonia is then added 
to the filtered solution of phosphoric acid and the resulting phosphate of am- 
monia being evaporated to dryness and heated to low redness in a platinum 
crucible, a hydrated phosphoric acid remains, in a fused state, which is known 
as glacial phosphoric acid, from its resemblance to ice. 

To exhibit many of its properties phosphoric acid must be first dissolved in 
water, when the compound will be found to be marked by an inconstancy and 
variableness in its characters, most unusual in a strong acid. This arises from 
the circumstance that it is not actual phosphoric acid which dissolves in water, 
any more than it is true sulphuric acid, which dissolves in water, when oil of 
vitriol is added to that fluid. It is a hydrate of both acids, which is soluble; 
the phosphate of water in the one case and the sulphate of w T ater in the other. 
But the phosphoric acid differs from the sulphuric, in a singular and almost 
peculiar capacity to form three different salts of water, instead of one only; 
and these three phosphates of water are all soluble without change, and exhi- 

* Ad. de Ch. et de Ph. L 2, pp. 151, 217, 329; and 10, p. 278. 



252 PHOSPHORUS. 

bit properties so different that they might be supposed to contain three diffe- 
rent acids. When the dry acid from the combustion of phosphorus is thrown 
into water, it produces a mixture, in variable proportions, of the three hydrates; 
but each of them may be had separately and in a state of purity by a particu- 
lar process. 

Terhydrate, or tribasic phosphate of water, 3HO-fP0 5 . — The common 
phosphate of soda of pharmacy may be had recourse to for all the hydrates of 
phosphoric acid; but it should be first dissolved and crystallized anew to purify 
it. To a warm solution of the pure phosphate of soda in a basin, add a solu- 
tion of acetate of lead in distilled water, so long as it occasions a precipitate; 
the phosphate of soda requires rather more than an equal weight of acetate of 
lead. The dense insoluble phosphate of lead, which precipitates, is washed, 
and being afterwards suspended in cold water, is decomposed by a stream of 
sulphuretted hydrogen gas sent through it. The liquor may then be warmed, 
to expel the excess of sulphuretted hydrogen, and filtered from the black sul- 
phuret of lead: it is very sour, and contains the terhydrate of phosphoric acid. 
The characters of this acid solution are, to give a yellow precipitate with 
nitrate of silver, to yield the common phosphate of soda when neutralized 
with carbonate of soda, to form salts which have invariably 3 atoms of base to 
1 of phosphoric acid, and to be unalterable by boiling its solution or keeping 
it for any length of time. The class of salts which this hydrate forms are the 
old phosphates, which have been long known, and it is convenient to allow 
them to be particularly distinguished as the phosphates or the common phos- 
phates. 

Deuto-hydrate of phosphoric acid, or bibasic phosphate of water, 2HO-f- 
P0 5 . — Dr. Clark first discovered that when the phosphate of soda is heated 
to redness, it is completely changed, and after being dissolved in water affords 
crystals of a new salt, which he named the pyrophosphate of soda, an obser- 
vation which led to the most important results.* If a solution of this salt, 
which it is not necessary to crystallize, be precipitated by acetate of lead, the 
insoluble salt of lead washed and decomposed by sulphuretted hydrogen, as 
before, an acid liquor is obtained which contains the deuto-hydrate of phos- 
phoric acid. It must not be warmed to expel the excess of sulphuretted hy- 
drogen, but be left in a shallow basin for 24 hours to permit the escape of 
that gas. This acid, when neutralized with carbonate of soda, gives Dr. 
Clark's pyrophosphate of soda. It also gives a white precipitate with nitrate 
of silver; all the sails which it forms, have uniformly two atoms of base. 
Their trivial name is the pyrophosphates, and since that term has come into 
general use, it is not likely to be superseded by the systematic, but rather 
cumbrous designation of bibasic phosphates. A dilute solution of the deuto- 
hydrate of phosphoric acid may be preserved for many months without change, 
but when the solution is exposed for some time to a high temperature, it 
passes entirely into the terhydrate. 

Protohydrate of phosphoric acid. — If the biphosphate of soda be heated to 
redness, a salt is formed, which treated in a similar manner with the last, gives 
an acid liquor, containing the protohydrate of phosphoric acid. To prepare 
the biphosphate itself, a solution of the terhydrate of phosphoric acid is added 
to a solution of common phosphate of soda, till it is found that a drop of the 
latter is no longer precipitated by chloride of barium. The biphosphate of 
soda, which is now in solution, can only be crystallized in cold weather. 
The glacial phosphoric acid also, is in general almost entirely the protohy- 
drate. This hydrate is characterized by producing a white precipitate in so- 

* Edinburgh Journal of Science, Vol. VII. p. 298, (1826;) or An. de Ch. et de Ph. t. 41. 
p. 27G. 



PHOSPHATES. 253 

lution of albumen, and in solutions of the salts of earths and metallic oxides 
precipitates which are remarkable semifluid bodies, or soft solids, without 
crystallization. 4 All these salts contain only one atom of base to one of acid, 
like the protohydrate of the acid itself. The trivial name mete/phosphates was 
applied to the class by myself, to mark the cause of the retention of peculiar 
properties by their acid, when free and in solution, namely, that it was not 
then simply phosphoric acid, but phosphoric acid together with water.* 
This is the'least stable of the hydrates of phosphoric acid being converted 
rapidly, by the ebullition of its solution, into the terhydrate. If the terms 
metaphospfwric acid and pyrophosphoric acid are employed at all, it is to be 
remembered that they are applicable to the proto and deutohydrates, and not 
to the acid itself, which is the same in all the hydrates. But to prevent the 
chance of misconception, metaphosphate of water and pyrophosphate of water 
might be substituted for these terms. 

A solution of the terhydrate of phosphoric acid, evaporated in vacuo over 
sulphuric acid, crystallizes in thin plates, which are extremely deliquescent. 
When heated to 400°, that hydrate loses a portion of water, and becomes a 
mixture of the deuto and protohydrates; and by heating it to redness for some 
time, the proportion of water may be reduced to one equivalent, or perhaps 
even less than this. But at that high temperature much of the hydrated phos- 
phoric acid passes off" in vapour. The solution of phosphoric acid is not poi- 
sonous, nor when concentrated does it act as a cautery, but it injures the teeth 
from its property of dissolving phosphate of lime. A solution of the latter 
salt in phosphoric acid has been prescribed in rickets, a disease which indi- 
cates a deficiency of earthy phosphates in the system. The phosphate of soda 
also is administered as a mild aperient; its taste is saline, but not disagreeably 
bitter. 

Phosphates. — The formation of three classes of phosphates from the three 
basic hydrates of phosphoric acid, affords an excellent illustration of the for- 
mation of compounds by substitution. The quantity of fixed base, such as 
soda, with which phosphoric acid combines in the humid way, being entirely 
regulated by the proportion of water previously in union with the acid, which 
is simply replaced by the fixed base. Thus, the protohydrate of phosphoric 
acid combines with no more than one, and the deutohydrate with no more 
than two proportions of soda, although three or a larger number of proportions 
of alkali be added to it. The excess of alkali remains free. Again, sup- 
posing an equivalent quantity of the terhydrate of phosphoric acid in solution, 
and one equivalent of soda added to it, one equivalent only of water is dis- 
placed, and two retained, and a phosphate formed, containing one of soda and 
two of water as bases, which is the salt alreadyadverted to under its old name 
of biphosphate of soda. Let a second equivalent of soda be added to this salt, 
and a second basic atom of water is displaced, and a tribasic salt produced, 
containing two of soda and one of water as bases, which is the common phos- 
phate of soda of pharmacy. A third equivalent of soda added to the last salt 
displaces the remaining atom of basic water, and a tribasic phosphate is formed, 
of which the whole three atoms of base are soda, and which has had the name 
of subphosphate of soda. But this last salt can unite with no more soda. 
The same three salts may be formed by means of the tribasic phosphate of 
water, in another manner. That acid hydrate decomposes chloride of sodium, 
but only to a certain extent, expelling hydrochloric acid, so as to acquire one 
of soda, and becoming 2HO, NaO + P0 5 , or the biphosphate of soda (apply- 
ing the old trivial terms;) the same acid hydrate applied to the carbonate or 

* Researches on the arseniates, phosphates and modifications of phosphoric acid. Phil. 
Trans. 1833, p. 253; or Phil. Mag. 3rd series, vol. 4, p. 401. 
22 



254 



PHOSPHORUS. 



the acetate of soda, can assume two proportions of soda, displacing- twice as 
much of the weaker carbonic and acetic acids, as of the hydrochloric acid, and 
so becomes HO, 2NaO-fP0 5 , or the common phosphate of soda; and the 
same acid hydrate applied to the hydrate of soda (caustic soda,) assumes three 
of soda, and becomes 3NaO-fP0 5 , or the subphosphate of soda. 

From soluble tribasic phosphates, such as those mentioned, insoluble salts 
may be precipitated, which are likewise tribasic, by adding solutions of most 
metallic salts. Tims 1 equivalent of the common phosphate of soda, added to 
the nitrate of silver in excess, decomposes 3 equivalents of it, and produces 
the yellow tribasic phosphate of silver, as explained in the following diagram, 
in which the name of a substance is understood to express one equivalent of 
it, and the figures, numbers of equivalents: — 

Before decomposition. After decomposition. 

2 Soda . . . . , 2 nitrate of soda 



{ 



Phosphate of soda *{ Water . . . 
Phosphoric acid 

f 2 Nitric acid. . 

Nitrate of silvers Nitric acid. . 

^3 Oxide of silver 




nitrate of water 



Phosphate of silver 
(Tribasic phosph. silv.) 



Here then, is exact mutual decomposition, but it is attended with a phenomenon 
which does not occur when other neutral salts decompose each other. The 
liquid does not remain neutral, but becomes highly acid after precipitation ; the 
reason is, that one of the new products is the nitrate of water, or hydrated nitric 
acid ; and consequently the products, although neutral in composition, are not 
neutral to test paper. 

The pyrophosphate of soda, which is bibasic, decomposes, on the other hand, 
two proportions of nitrate of silver, and gives a pyrophosphate or bibasic phos- 
phate of silver, which is a white precipitate; thus — 



Before decomposition. 

Pyrophosphate $ 

of soda / 



2 Nitrate 
silver 



of 



2 Soda ... 
Phosphoric acid 

2 Nitric acid . 
2 Oxide of silver 




After decomposition. 
2 nitrate of soda 



Pyrophos. of silver 
(Bibasic phos. silv.) 



Here there is no salt of water, among the products, and consequently the liquid 
is neutral after precipitation. 

The metaphosphate of soda, which is monobasic, like the sulphates, nitrates 
and other familiar salts, decomposes, like them, but one proportion of nitrate of 
silver, and forms a white precipitate ; thus — 



Before decomposition. 
Metaphosph. C Soda . . . . 

of soda I Phosphoric acid . 
Nitrate of C Nitric acid . . 

silver ? Oxide of silver . 




After decomposition. 

Nitrate of soda 



Metaphosphate of silv. 
(Monobasic phos. silv.) 



If acetate or nitrate of lead be substituted for nitrate of silver in these decom- 
positions, a tribasic, bibasic or monobasic salt of lead is obtained in the same 
manner ; and these salts, again, decomposed by sulphuretted hydrogen, afford 



PHOSPHATES. 255 

respectively the terhydrate, deutohydrate and protohydrate of phosphoric acid. 
The statement of the decomposition of the metaphosphate of lead by sulphuretted 
hydrogen, will be sufficient to explain how a hydrate of phosphoric acid comes 
to be formed in all these cases : — 

Before decomposition. After decomposition. 

, c C Phosphoric acid 7 Metaphosph. of water 

Metaphosph.on 0xygen > . # 217 (Protohydr . of phos . ac<) 



lead 



^Lead 




Sulphuretted C Hydrogen 
hydrogen ^Sulphur . . ,^___^ Sulphuret of lead. 

It will be observed that the sulphuretted hydrogen forms an equivalent of 
water, at the same time that it throws down the sulphuret of lead; in this phos- 
phate of lead, there is only one equivalent of oxide of lead, and consequently 
only one equivalent of water formed, but if there were two or three equivalents 
of oxide, there would be two or three equivalents of water formed; or the phos- 
phoric acid is always left in combination with as many proportions of water as 
it previously possessed of oxide of lead. Thus the different hydrates of phos- 
phoric acid are obtained, from the decomposition of the corresponding phos- 
phates of lead. 

In no decomposition of this kind, is there any transition from one class of 
phosphates into another, because the decompositions are always mutual, and 
the products of a neutral character. Hence an argument for retaining the trivial 
names, common phosphates, pyrophosphates and metaphosphates, for there is 
no changing, in decompositions by the humid way, from one to the other, and 
the salts comport themselves so far quite as if they had different acids. The 
circumstances may now be noticed, in which a transition from the one class to 
the other does occur : 

1st. — Changes without the intervention of a high temperature. When so- 
lutions of the metaphosphate and pyrophosphate of water are warmed, they pass 
gradually into the state of common phosphate, combining with an additional 
quantity of water ; and the metaphosphate of water appears then to become at 
once common phosphate, without passing through the intermediate state of hy- 
dration of the pyrophosphate. The metaphosphate of barytes also, which is an 
insoluble salt, is gradually dissolved, when boiled in water, and becomes com- 
mon phosphate. The easy transition from the one class of phosphates to the 
other, then witnessed, forbids the supposition that they contain different acids. 
It is remarkable that we may have pyrophosphates of potash and of ammonia 
in solution, and perfectly stable, but not in the dry state. These salts do not 
crystallize. The pyrophosphate, of ammonia, indeed, when allowed to evaporate 
spontaneously, appears to crystallize, but in the act of becoming solid, it passes 
into common phosphate (the biphosphate of ammonia, 2HO, NH 4 0+P0 5 ,) 
which is the salt that forms crystals. 

2nd. — Changes with the intervention of a high temperature. If a single 
equivalent of phosphoric acid, anhydrous, or in any state of hydration, be cal- 
cined, at a temperature which may fall a little short of red heat, (1°) with a 
single equivalent of soda or its carbonate, the metaphosphate of soda will be 
formed ; (2°) with two equivalents of soda or its carbonate, the pyrophosphate 
of soda will be formed ; and (3° ) with three equivalents of soda or its carbonate, 
a common phosphate of soda will be formed. Hence, the formation of none of 
these classes is peculiarly the effect of a high temperature. Again, a tribasic 
phosphate, containing one or two equivalents of a volatile base, such as water 
or ammonia, loses the volatile base, when ignited, and the acid remains in com- 



256 CHLORINE. 

bination with the fixed base. Hence, common phosphate of soda (HO, 2NaO 
+P0 5 ) is converted by heat into pyrophosphate (2NaO-fP0 5 ,) the original 
observation of Dr. Clark; and the biphosphate of soda (2HO, NaO+P0 5 ) into 
metaphosphate of soda (Na04-P0 5 .) The acid remains in combination with 
the fixed base left with it, and the salt produced may be dissolved in water 
without assuming basic water. 

The metaphosphate of soda is susceptible of a remarkable conversion, by the 
agency of a certain temperature, and exhibits a change of nature, without a 
change of composition, such as often occurs in organic compounds, but rarely 
admits of so satisfactory an explanation. This particular salt, in common with 
all the other phosphates, combines with water, which becomes attached to the 
salt, in the state of constitutional water, or water of crystallization. The meta- 
phosphate of soda, so hydrated, when dried at 212°, retains one equivalent of 
water, but that water is not basic, for on dissolving the salt again, it is found 
still to be a metaphosphate. But let this hydrated metaphosphate be heated to 
300°, and without losing any thing, it changes completely, and becomes a 
pyrophosphate, the water which was constitutional before, being now basic. 
The formulae of the salt in its two states, exhibits to the eye the nature of the 
internal change which has occurred in it : 

1. — Hydrated metaphosphate of soda . NaO, P0 5 +HO, 
2. — Pyrophosphate of soda and water . NaO, HO-f-P0 5 . 

In describing the three classes of phosphates, with their relations to each other, 
I have been thus minute, partly because considerable explanatory detail was 
required, from the extent of the subject, but principally that we might avail our- 
selves of the light which the phosphates have thrown upon the constitution of 
the class of organic acids, and upon the function of water in many compounds. 
Indeed, phosphoric acid is one of the links by which mineral and organic com- 
pounds are connected. And it may be reasonably supposed that it is that pliancy 
of constitution, which we have studied, that peculiarly adapts this, above all 
other mineral acids, to the wants of the animal economy. 



SECTION X. 

CHLORINE. 

Eq. 442.65 or 35.47; CI; density 2440; 



This body was discovered by Seheele in 1774, but was believed to be of a 
compound nature till Gay-Lussac and Thenard in 1809, showed that it might 
reasonably be considered a simple substance. It is to the powerful advocacy 
of Davy, however, who entered upon the investigation shortly afterwards, that 
the establishment of the elementary character of chlorine is principally due, and 
to him it is indebted for the name it now bears, which is derived from x^apos, 
yellowish green, and refers to its colour as a gas, elementary bodies being gene- 
rally named from some remarkable quality or important circumstance in their 
history. Chlorine is the leading member of a well-marked natural family, to 
which also bromine, iodine and fluorine belong. Phosphorus, carbon, hydrogen, 
sulphur, and most of the preceding elementary bodies, have little or no action 
upon each other, or upon the mass of hydrogenous, carbonaceous and metallic 
bodies to which they are exposed in the material world ; all these substances 
being too similar in nature, to have much affinity for each other. But the class 
to which chlorine belongs, ranks apart, and, with a mutual indifference to each 
other, they exhibit an intense affinity for the members of the other great and 



PREPARATION. 



257 



prevailing class, an affinity so general as to give the chlorine family the character 
of extraordinary chemical activity, and to preclude the possibility of any member 
of the class existing in a free and uncombined state in nature. The compounds 
again of the chlorine class, with the exception of those of fluorine, are remarka- 
ble for solubility, and consequently find a place among the saline constituents of 
sea water, and are of comparatively rare occurrence in the mineral kingdom ; 
with the single exception of chloride of sodium, which besides being present in 
large quantity in sea water, forms extensive beds of rock salt in certain geological 
formations. 

Preparation. — The fuming hydrochloric acid or muriatic acid (as it is also 
called) of commerce, is a solution in water of hydrochloric acid gas, a compound 
of chlorine and hydrogen, from which chlorine gas is easily procured. The 
liberation of chlorine results from contact of the acid named with peroxide of 
manganese, and the reaction which then occurs is made most obvious in the 
following mode of conducting the experiment. A few ounces of the strongly 
fuming hydrochloric acid, are introduced into a flask «, with a perforated cork 
and tube b, upon which a bulb or two have been expanded; and that tube is 

Fig. 80. 




Tfcgpftfffift^^ 




Jk 



connected by means of a short caoutchouc tube or adopter, with the tube c, 
containing fragments of chloride of calcium, and the last is connected in a 
similar manner with the exit tube d, which descends to the bottom of a dry 
and empty bottle e. Upon applying the spirit lamp, burning with a small 
flame to a, the liquid in the flask soon begins to boil, and the hydrochloric gas 
passes off, depositing perhaps a little moisture in the bulbs of 6, which may 
be kept cool by wet blotting paper, and being completely dried in passing 
through c. It is conveyed by d, to the bottom of the bottle e, and finally 
escapes and produces white fumes in the atmosphere, after displacing the air of 
that bottle. The hydrochloric gas is obtained in e unchanged, and will redden 
and not bleach a little blue infusion of litmus poured into e. But between the 
tube c and d, let another tube be now interposed having a pair of bulbs blown 
upon it/ and g, (Fig. 81) one of which/ contains a quantity of pounded 
anhydrous peroxide of manganese; the bottle e remaining as before. Then 
upon applying heat to the manganese bulb/, the hydrochloric gas will be found to 
suffer decomposition as it traverses that bulb, its hydrogen uniting with the 
oxygen of the manganese and forming water, which will condense in drops in 
g, which may be kept cool, and disengaged chlorine proceeds on to e, in 
which that gas will be perceptible from its yellow tint, and more so by bleach- 
ing the infusion of reddened litmus remaining in e. If the transmission of 

22* 



258 



CHLORINE. 
Fig. 81. 




hydrochloric acid over the peroxide of manganese be continued for sufficient 
time, the latter loses all its oxygen, and the metal remains in the state of pro- 
tochloride. Indeed only one half of the chlorine of the decomposed hydrochlo- 
ric acid gas, is obtained as gas, the other half being retained by the manganese, 
as will appear by the following diagram: 

Process for chlorine from hydrochloric acid and peroxide of manganese. 



Before decomposition. 

Hydrochloric J 

acid / 



C Chlorine. 
I Hydrogen. 
f Oxygen. . 
< Manganese 
^Oxygen. . 
C Chlorine. . 
I Hydrogen. 

Or in symbols; Mn0 2 + 2HC1 = MnCl and 2HO 



Peroxide of man- 
ganese 

Hydrochloric 
acid 




After decomposition. 
— Chlorine. 
Water. 



Chloride of manganese. 

Water. 
ndCl. 



Fig. 82. 



The most convenient method of preparing chlorine gas is by mixing in a 
flask 2 ounces of peroxide of manganese, with 6 ounce measures of hydro- 
chloric acid, diluted with an ounce or two of water to prevent it fuming. Ef- 
fervescence, from escape of gas, takes place in the cold, but is greatly pro- 
moted by the application of a gentle heat. This gas is collected over water, 

of which the temperature should not be 
less than 90°, otherwise a great waste of 
the gas occurs from its solution in the wa- 
ter, and also a consequent annoyance to 
the operator from the escape of the chlo- 
rine into the atmosphere, by evaporation 
from the surface of the water trough. If 
the gas is not to be used immediately, but 
preserved, it should be collected in bottles, 
' into which when filled with gas, their 
stoppers greased, should be inserted before they are removed from the trough. 
Before the gas obtained by this process can be considered as pure, it should 
always be transmitted through water, to remove hydrochloric acid; an interme- 
diate Wolfe's bottle containing water, may be employed to wash the gas, as 
was done with sulphurous acid. If the gas is to be dried, it must be sent 
through a tube containing chloride of calcium, of two or three feet in length, 
great difficulty being experienced in drying this gas in a perfect manner, owing 




PROPERTIES. 



259 



to its low diffusive power: it is three times more difficult to dry than carbonic 
acid. Chlorine cannot be collected over mercury, as it combines at once with 
that metal. 

A somewhat different process for the preparation of chlorine is generally 
followed on the large scale. About 6 parts of manganese with 8 of common 
salt are introduced into a large leaden vessel, of a form nearly globular, as re- 
presented in the figure, and 5 or 6 feet in diameter, and to these are added as 
much of the unconcentrated sulphuric acid of the leaden chambers, as is equi- 
valent to 13 parts of oil of vitriol. The leaden vessel is placed in an iron pan, 
or has an outer casing d c, as represented in the figure, and to heat the mate- 
rials, steam is admitted by d into the space between the bottom and outer case- 



Fig. 



ing. In the figure, which is a section of the 
leaden retort, a represents the tube by which 
the chlorine escapes, b a large opening for in- 
troducing the solid material covered by a lid, 
or water valve, from the edges dipping into a 
channel containing water, e a twisted leaden 
funnel for introducing the acid, / a wooden 
agitator, and c a discharge tube, by which the 
waste materials are run orf after the process is 
finished. A retort of lead cannot be used with 
safety, with peroxide of manganese and hydro- 
chloric acid for chlorine, owing to the action of 
the acid upon the lead, and the evolution of 
hydrogen gas, which produces a spontaneously 
explosive mixture with chlorine. A material 
for the vessel, which might be substituted for glass, is still a desideratum in 
that process. Vessels of silver are acted upon, the chloride of silver appear- 
ing not to be absolutely insoluble in hydrochloric acid. In the reaction which 
occurs in the leaden retort, it may be supposed, either that hydrochloric acid is 
first liberated from chloride of sodium by sulphuric acid, and afterwards de- 
composed by peroxide of manganese, as in the preceding experiment; or that 
sulphates of manganese and soda are simultaneously formed, and chlorine libe- 
rated in consequence, as stated in the following diagram, in which the names 
express (as usual) single equivalents : 

Process for chlorine from chloride of sodium (common salt,) peroxide of 
manganese and sulphuric acid : 




Before decomposition. 
Chloride of C Chlorine 

sodium ^ Sodium 

Sulphuric acid . . Sulphuric acid. . 
Peroxide of C Oxygen 

manganese ^Protox. manganese 
Sulphuric acid . . Sulphuric acid. . .. 

Or in symbols; 



After decomposition. 
. Chlorine. 

Sulphate of soda. 



Sulphate of manganese. 



NaCl and 2S0 3 and Mn0 2 = NaO.SO, and MnO,S0 3 and CL 

Properties.--- Chlorine is a dense gas of a pale yellow colour, having a pe- 
culiar suffocating odour, absolutely intolerable even when largely diluted with 
air. and occasioning great irritation in the trachea, with coughing, and oppres- 
sion of the chest. Some relief from these effects is experienced from the in- 



260 CHLORINE. 

halation of the vapour of ether or alcohol. The density of chlorine gas is, by- 
experiment 2470, by theory 2440. Under a pressure of about 4 atmospheres, 
chlorine condenses into a limpid liquid of a bright yellow colour, of a sp. gr. 
about 1.33, and which has not been frozen. Water at 60° dissolves twice its 
volume of this gas, and acquires the yellowish colour, odour and other pro- 
perties of chlorine. To form chlorine water, a stout bottle filled with the gas 
at the tepid water trough, may be closed with a good cork and removed to a 
basin of cold water; on loosening the cork with the head of the bottle under 
water, a little water will enter it, from the contraction of the gas by cooling; 
and this water may be agitated in contact with the gas, by a lateral movement 
of the bottle, without removing it from the water; on loosening the cork again 
more water will be found to enter the bottle, and by repeating the agitation 
and admission of water, the whole gas (if pure) is absorbed, and the bottle is 
in the end filled with water, which of course contains an equal volume of 
chlorine gas. With water near its freezing point, chlorine combines and forms 
a crystalline hydrate, which Faraday found to contain 10 atoms of water. 
Hence, chlorine gas cannot be collected at all over water, below 40°. Ex- 
posed to light, chlorine water soon loses its properties, water being decom- 
posed and hydrochloric acid formed, -with the evolution of oxygen gas. But 
it may be preserved for a long time in a stoneware bottle. When diluted so 
far that the water does not contain above 1 or 1§ per cent, of its bulk of chlo- 
rine, the odour is by no means strong, and such a solution may be employed 
in bleaching, without inconvenience to the workmen, although a combination 
of chlorine with hydrate of lime, called the chloride of lime, is generally pre- 
ferred for that purpose. 

Chlorine does not in any circumstances unite directly with oxygen, although 
several compounds of these elements can be formed; nor does it combine di- 
rectly with nitrogen or carbon. Chlorine and hydrogen gases may be mixed 
and preserved in the dark without uniting, but combination is determined with 
explosion by spongy platinum or the electric spark, or by exposure to the 
direct rays of the sun; even under the diffuse light of day, combination of the 
gases takes place rapidly, but without explosion. Chlorine indeed has a 
strong affinity for hydrogen, and decomposes most bodies containing that ele- 
ment, hydrochloric acid being always formed. In plunging an ignited taper 
into chlorine gas, its flame is extinguished, but the column of oily vapour 
risihg from the wick is rekindled by the chlorine, and the hydrogenous part 
of the combustible continues to burn with a red and smoky flame, which ex- 
pires on removing the taper into air. Paper dipped in oil of turpentine takes 
fire spontaneously in this gas, and the oil burns with the deposition of a large 
quantity of carbon. The affinity of chlorine for most metals'is equally great: 
antimony, arsenic and several others, showered in powder into this gas, take 
fire and produce a brilliant combustion. Chlorine is absorbed by alcohol and 
many other organic substances, when it generally eliminates more or less hy- 
drogen, as hydrochloric acid, and enters also. by substitution into the original 
compound, in the place of that hydrogen, thus producing many new com- 
pounds, such as chloral from alcohol. It bleaches all vegetable and animal 
colouring matters, and is believed then to act in that manner. The colours 
are destroyed and cannot be revived by any treatment. 

Chlorine when free is easily recognised by its odour and bleaching power, 
and in the soluble chlorides, by producing with nitrate of silver, a white curdy 
precipitate of chloride of silver, which is soluble in ammonia, but not soluble 
in cold or boiling nitric acid. 

Uses. — Chemistry has presented to the arts few substances of which the 
applications are more valuable. Chlorine is the discolouring agent of the mo- 
dern process of bleaching, which as it is generally conducted with cotton 



CHLORIDES. 



261 



goods, consists of the following operations. The cloth, after being well 
washed, is boiled first in lime-water and then in caustic soda, which remove 
from it certain resinous matters soluble in alkali. It is then steeped in a solu- 
tion of chloride of lime, so dilute as just to taste distinctly, which has little or 
no perceptible effect in whitening it: but the cloth is afterwards thrown into 
water acidulated with sulphuric acid, of sp. gr. between 1.010 and 1.020, 
when a minute disengagement of chlorine takes place throughout the substance 
of the cloth, and it immediately assumes a bleached appearance. The cloth 
is boiled a second time with caustic soda, and digested again in dilute chloride 
of lime, and in dilute sulphuric acid as before. The acid favours the bleaching 
action, and is required besides to remove the caustic alkali, a portion of which 
adheres pertinaciously to the cloth. The fibre of the cloth is not injured by 
dilute sulphuric acid, although digested in it for days, provided the cloth is not 
allowed to dry with the acid in it, or left above the surface of the liquor. But 
it is very necessary to wash well after the last souring, to get rid of every 
trace of acid, with which view the cloth may be passed through warm water, 
as a precautionary measure to finish with. 

When employed for the purpose of disinfecting the wards of hospitals, 
chlorine is most conveniently evolved from chloride of lime, of which a pound 
may be mixed with water in a hand-basin, and a pound measure of hydro- 
chloric acid poured upon it. The gas is evolved from these materials without 
heat. * 

Chlorides. — Chlorine combines with all the metals and in the same propor- 
tions as oxygen. With the exception of the chlorides of silver and lead, and 
subchlorides of copper and mercury, these compounds are soluble and sapid, 
and they possess in an eminent degree the saline character. Indeed common 
salt, the chloride of sodium, has given its name to the class of salts, and chlo- 
rine is the type of salt-radicals or hulogenous (salt-producing) bodies. Chlo- 
rides of metals belonging to different classes often combine together and form 
double chlorides; the chlorides of the potassium family, in particular, with 
some chlorides of the inagnesian family, as with chloride of copper, with chlo- 
ride of mercury, with both the chlorides of tin, and with perchlorides gene- 
rally. A chloride and oxide of the same metal (excepting the potassium 
family) often combine together, forming oxic/dorides, which are in general of 
slight solubility. 

Chlorine is also absorbed by alkaline solutions, and combinations are formed 
which bleach and exhibit many of the properties of the free element. The 
state of the chlorine in these compounds and also in dry chloride of lime, 
formed by exposing hydrate of lime to chlorine gas, is still matter of uncer- 
tainty. But they are not permanent compounds, and the chlorine eventually 
acts upon the metallic oxide, so as to produce a chloride, and a chlorate of 
the metal as will be afterwards explained. 

The following chlorides of the non-metallic elements will now be particu- 
larly described: 

Hydrochloric acid. . . H CI 

Hypochlorous acid. . . CI 

Peroxide of chlorine. . . CI 4 

Chloric acid CI 5 

Hyperchloric acid. . . . CI O- 

Chloride of nitrogen. . . N Cl 3 

Perchloride of carbon. . . C 4 C1 6 

Protochloride of carbon. . C 4 C1 4 



Subchloride of carbon. 


. c 4 ci 2 


Chlorocarbonic acid. . 


. CO,Cl 


Chloride of boron. 


. BC1 3 


Chloride of silicon. 


. SiCl 3 


Chloride of sulphur. . 


. S 2 C1 


Bichloride of sulphur. 


. SC1 2 


Terchl. of phosphorus. 


. PCL 


Perchl. of phosphorus. 


. pci 5 



262 



CHLORINE. 



HYDROCHLORIC ACID. 
Syn. chlorhydric acid (Thenard,) (Hare,) muriatic acid. Eq, 455.15 
or 36.47; C1H; density 1269.5; 



This acid is one of the most frequently employed re-agents in chemical 
operations, and has long been known under the names of spirit of salt, marine 
acid, and muriatic acid (from murias, sea-salt.) It was first obtained by 
Priestley in its pure form of a gas, in 1772. 

Preparation. — Hydrochloric acid is always obtained by the action of oil of 
vitriol upon common salt. When the process is conducted on a small scale 
and in a glass retort, equal weights of common salt, oil of vitriol and water 
may be taken. The oil of vitriol being mixed with l-3rd of the water in a 
thin flask, and cooled, is poured upon the salt contained in a capacious retort. 
A clean flask containing the remaining 2-3rds of the water is then adapted to 
the retort as a condenser, as in the distillatory apparatus figured at page 63. 
Upon applying heat to the retort, hydrochloric acid gas comes off and is con- 
densed in the receiver, affording an aqueous solution of the acid, of sp. gr. 
1.170, and which contains about 37 per cent, of dry acid; while a mixture of 
sulphate and bisulphate of soda remains in the retort. Supposing single equi- 
valents of oil of vitriol and chloride of sodium to be employed, to which the 
preceding proportions approximate, then the rationale of the action is as fol- 
lows: 



Process for hydrochloric acid : 

Before decomposition. 
733 Chloride of C Chlorine 
sodium / Sodium 



442 
291 



f Hydrogen. 12^ 
613| Oil of vitr. < Oxygen . 100 
(_Sulphu. acid 501 




After decomposition. 
454i hydroc. acid 



892 sulph. of soda 



1346A 



13461 



13461 



Or in symbols; NaCl and HO,S0 3 == HC1 and NaO, S0 3 . 

This process is more economically conducted on the large scale in a cast iron 
cylinder, about 5 feet in length and 2<| in diameter, laid upon its side, which has 
moveable ends, generally composed of a thin paving, stone cut into a circular 
disc and divided into two unequal segments. A charge of three or four cwt, 
of salt is introduced into the retort, and after the bottom is heated, undiluted 
oil of vitriol is added in a gradual manner by means of a long funnel, and in 
proportion not exceeding the equivalent for the chloride of sodium. In such 
circumstances, the lower part of the cylinder exposed to the sulphuric acid is 
not much acted upon, while the roof of the cylinder is protected from the hy- 
drochloric acid fumes by a coating of fire-clay or thin split bricks. The hydro- 
chloric acid gas is conducted by a strong glass tube into a series of large jars of 
salt-glaze ware, connected with each other like Wolfe's bottles, and containing 
water in which the acid condenses. 

Properties.— Hydrochloric acid is obtained in the state of gas by boiling an 
ounce or two of the fuming aqueous solution, in a small retort, or by pouring 



HYDROCHLORIC ACID. 



263 



oil of vitriol upon a small quantity of salt in a retort, and is collected over mer- 
cury. It is an invisible gas, of a pungent acid odour, and produces white fumes 
when allowed to escape, by condensing the moisture in the air. By a pressure 
of 40 atmospheres at 50° it is condensed into a liquid, of sp. gr. 1.27. It is quite 
irrespirable but much less irritating than chlorine ; it is not decomposed by heat 
alone, nor when heated in contact with charcoal. Hydrochloric acid extin- 
guishes combustion, and is not made, to unite with oxygen by heat ; but when 
electric sparks are passed through a mixture of this gas and oxygen, decompo- 
sition takes place to a small extent, water being formed and chlorine liberated. 
It is composed by volume, of one combining measure or two volumes of each 
of its constituents, united without condensation ; so that its combining measure 
is 4 volumes, and its theoretical density 1269.5. It may be formed directly by 
the union of its elements. 

If a few drops of water or a fragment of ice be thrown up into a jar of hydro- 
chloric acid over mercury, the gas is completely absorbed in a few seconds ; or 
if a stout bottle filled with this gas be closed with the thumb and opened under 
water, an instantaneous condensation of the gas takes place, water rushing into 
the bottle as into a vacuum. Dr. Thomson finds that 1 cubic inch of water 
absorbs 418 cubic inches of gas, at 69°, and becomes 1.34 cubic inch. He has 
constructed the following table, from experiment, of the specific gravity of hy- 
drochloric acid of determinate strengths.* 



HYDROCHLORIC ACID. 



Atoms of Water 


Real Acid in 100 


Specific 


! Atoms of Wa'er 


Real Acid in 100 


Specific 


to 1 of Acid. 


of the liquid. 


Gravity. 


to 1 of Acid. 


of the liquid. 


Gravity. 


6 


40.66 


1.203 


14 


22.700 


1.1060 


7 


37.00 


1.179 


15 


21.512 


1.1008 


8 


33.95 


1.162 


16 


20.442 


1.0960 


9 


31.35 


1.149 


17 


19.474 


1.0902 


10 


29.13 


1.139 


18 


18.590 


1.0860 


11 


27.21 


1.1285 


19 


17.790 


1.0820 


12 


25.52 


1.1197 


20 


17.051 


1.07S0 


13 


24.03 


1.1127 









To this may be added the following useful table, for which we are indebted 
to Mr. E. Davy : — 

HYDROCHLORIC ACID. 



Specific 


Quantity of Acid 


Specific 


Quantity of Acid 


Gravity. 


per cent. 


Gravity. 


percent. 


1.21 


42.43 


1.10 


20.20 


1.20 


40.80 


1.09 


18.18 


1.19 


38.38 


1.08 


16.16 


1.18 


36.36 


1.07 


14.14 


1.17 


34.34 


1.06 


12.12 


1.16 


32.32 


1.05 


10.10 


1.15 


30.30 


1.04 


8 08 


1.14 


28.28 


1.03 


6.00 


1.13 


26.26 


1.02 


4.04 


1.12 


24.24 


1.01 


2.02 


1.11 


22.22 







* First Principles of Chemistry. 



264 CHLORINE. 

It thus appears that the strongest hydrochloric acid that can be easily formed 
contains six atoms of water; this liquid allows acid to escape when evaporated 
in air, and comes according to an observation of my own, to contain 12 atoms 
of water to 1 of acid. Distilled in a retort, it was found, by Dr. Dalton, to lose 
more acid than water till it attained the specific gravity 1.094, when its boiling 
point attained a maximum 230°, and the acid then distilled over unchanged. 
Dr. Clark finds by careful experiments that the acid which is unalterable by 
distillation, contains 16.4 equivalents of water. 

The concentrated acid is a colourless liquid, fuming strongly in air, highly 
acid, but less corrosive than sulphuric acid; not poisonous when diluted. 
It is decomposed by substances which yield oxygen readily, such as metallic 
peroxides and nitric acid, which cause an evolution of chlorine, by oxidating 
the hydrogen of the hydrochloric acid. A mixture of 1 measure of nitric and 
2 measures of muriatic acid forms aqua regia, which dissolves the less oxidable 
metals, such as gold and platinum, through the agency of the disengaged chlorine. 

The hydrochloric acid of commerce has a yellow or straw colour, which is 
generally due to a little iron, but may be occasionally produced by organic 
matter, as it is sometimes destroyed by light. This acid is rarely free from 
sulphuric acid, the presence of which is detected by the appearance of a white 
precipitate of sulphate of barytes, on the addition of chloride of barium to the 
hydrochloric acid diluted with 4 or 5 times its bulk of distilled water. Sulphu- 
rous acid is also occasionally present in commercial hydrochloric acid, and is 
indicated by the addition of a few crystals of protochloride of tin, which salt de- 
composes sulphurous acid and occasions, after standing some time, a brown 
precipitate containing sulphur in combination with tin (Girardin.) To purify 
hydrochloric acid, it should be diluted till its sp. gr. is about 1.1, for which the 
strongest acid requires an equal volume of water ; and with the addition of a 
portion of chloride of barium, the acid should then be redistilled. As the acid 
brings over enough of water to condense it, Liebig's condensing apparatus 
(page 64) can be used in this distillation. The pure acid thus obtained is strong 
enough for almost every purpose, and has the advantage of not fuming in the 
air. Hydrochloric acid, like chlorine and the soluble chlorides, gives with nitrate 
of silver a white curdy precipitate, the chloride of silver, soluble in ammonia, but 
not dissolved by hot or cold nitric acid. 

Hydrochloric acid belongs to the class of hydrogen acids, or hydracids, which 
do not exist in salts. On neutralizing this acid with soda or any other basic 
oxide, no hydrochlorate of soda is formed, but the hydrogen of the acid with 
the oxygen of the soda forming water, the chlorine and sodium combine and 
produce a metallic chloride. Zinc and the other metals which dissolve in dilute 
sulphuric acid, with evolution of hydrogen, dissolve with equal facility in this 
acid, with the same evolution of hydrogen, and a chloride of the metal is formed. 



COMPOUNDS OF CHLORINE AND OXYGEN. 

Chlorine and oxygen gases exhibit no disposition to combine with each other 
in any circumstances, but this is not inconsistent with their forming a series of 
compounds, as nitrogen and oxygen, which exhibit a similar indifference to each 
other also do. The oxides of chlorine are four in number, and all bear acid 
appellations, namely : 

Hypochlorous acid . . . . CI O 

Chlorous acid . . . . CI 4 

Chloric acid CI 5 

Hyperchloric acid CI 7 



HYPOCHLOROUS ACID. 265 

Hypochlorous and chloric acids are always primarily formed by a reaction 
occurring between chlorine and two different classes of metallic oxides; and the 
chlorous and hyperchloric acids again are derived from the decomposition of 
chloric acid. 

Hypochlorous acid. — The discovery of this compound was made by M. 
Balard in 1834.* It is formed by the action of chlorine upon the red oxide 
of mercury. If to a two-pound bottle of chlorine gas, 6 drachms of red oxide 
of mercury in fine powder be added with H ounce of water, the chlorine will 
be found to be rapidly absorbed on agitation. One portion of the chlorine 
unites with the oxygen of the metallic oxide, and becomes hypochlorous acid, 
which is dissolved by the water, while another portion forms a chloride with 
the metal, which chloride unites with a portion of undecomposed oxide, and 
forms an insoluble oxichloride. The liquid may be poured off and allowed 
to settle; it is a solution of hypochlorous acid, with generally a little chloride 
of mercury. This reaction is expressed in the following diagram: — 



FORMATION OF HYPOCHLOROUS ACID. 

Before decomposition. After decomposition. 

Chlorine Chlorine . . . Hypochlorous acid 



Oxide of Merc. 5°*yg en 
I Mercury 



Chlorine Chlorine . . "-*-» Chloride of Merc. 

Oxide of Merc. . Oxide of Mercury, Oxide of Mercury 



combined. 



Or in symbols; 2 CI and 2 HgO == CIO and HgCl, HgO. But the oxichlo- 
ride formed, seems not always to contain the same proportion of oxide. The 
proportion of hypochlorous acid in the liquid may be increased, by intro- 
ducing the same solution in a second bottle of'chlorine, with an additional 
quantity of red oxide of mercury. The oxide of "zinc and black oxide of cop- 
per, diffused through water, and exposed to chlorine, give rise to a similar 
formation of hypochlorous acid. 

The pure hypochlorous acid is a gas, which Balard succeeded in disen- 
gaging by passing up fragments of nitrate of lime into the liquid acid above 
mercury, in a jar of the mercurial trough. By dissolving in the water, that 
salt causes the evolution of the gas, which collects in the upper part of the 
jar, and is defended from contact with the mercury, which absorbs it, by the 
intervention of the saline solution. 

The gas is of a pale yellow colour, very similar to chlorine. It is com- 
posed of 2 volumes of chlorine and 1 volume of oxygen, condensed into 2 
volumes, and is resolved by a slight elevation of temperature into its consti- 
tuent gases. This decomposition is attended with an explosion of such vio- 
lence as to project the jar from the trough, but not to break it to pieces, and 
may occur on transferring the gas from one jar into another. Water dissolves 
about 100 volumes of this gas. 

The original solution of hypochlorous acid may be distilled, but much of 
the acid is decomposed unless the operation be conducted in vacuo. It is then 
obtained as a transparent liquid of a slightly yellow colour. It displaces the 
carbonic acid of alkaline carbonates, but has not much analogy to other acids. 
Its taste is extremely strong and acrid, but not sour, and its odour penetrating 
and different from, although somewhat similar to chlorine. It attacks the epi- 

* An. de Ch. et de Ph. t. 57, p. 225, or Taylor's Scientific Memoirs, vol. I, p, 269. 
23 



266 CHLORINE. 

dermis like nitric acid, and is exceedingly corrosive. It bleaches instantly? 
like chlorine, and is a powerful oxidizing agent. When concentrated it is ex- 
ceedingly unstable, small bubbles of chlorine gas being spontaneously evolved 
and chloric acid formed. This decomposition is promoted by the presence 
of angular bodies, such as pounded glass, and also by heat and light. 

Of the elementary bodies, hydrogen has no action upon hypochlorous acid. 
Sulphur, selenium, phosphorus and arsenic act upon it with great energy, and 
are all of them raised to their highest degree of oxidation, with the evolution 
of chlorine gas; selenium even being converted into selenic acid, although it 
is only converted into selenious acid by the action of nitric acid. Iodine is 
also converted into iodip acid. Iron filings decompose it immediately and 
chlorine comes off. Copper and mercury combine with both elements of the 
acid and form oxichlorides. Many other metals are not acted upon by it, 
unless another acid be present, such as zinc, tin, antimony and lead. Silver 
has a different action upon hypochlorous acid from that of most bodies, com- 
bining with its chlorine and causing an evolution of oxygen gas. Hydrochlo- 
ric and hypochlorous acids mutually decompose each other, water being 
formed, and chlorine liberated; the presence of soluble chlorides is equally in- 
compatible with the existence of hypochlorous acid. 

Hypochlorites. — The direct combination of hypochlorous acid with pow- 
erful bases is accompanied by heat, which is apt to convert the hypo- 
chlorite into a mixture of chlorate and chloride; but by adding the acid in 
a gradual manner to the alkaline solution, hypochlorites of potash, soda, 
lime, barytes and strontian may be formed, and may even be obtained in a 
solid state by evaporation in vacuo, if a considerable excess of alkali be pre- 
sent, which appears to give a certain degree of stability to these salts. They 
bleach powerfully, and their odour and colour are identically the same as the 
corresponding decolourizing compounds of chlorine, from which it is impos- 
sible to'distinguish them by their physical properties. They are salts of a 
very changeable constitution; a slight increase of temperature, the influence 
of solar light, even of diffused light, converts them into chlorides and chlo- 
rates. It is the opinion of M. Balard that bleaching powder, formed by ex- 
posing hydrate of lime to chlorine, is a mixture of hypochlorite of lime and 
chloride of calcium; but to this subject I shall again return under the salts of 
lime. 

The euchlorine gas of Davy, to which he assigned the composition of hy- 
pochlorous acid, has been found to be a mixture of chlorine and chlorous acid 
gases. That mixture is obtained by the action of hydrochloric acid of sp. gr. 
1.1 upon chlorate of potash, aided by a gentle heat. It has a very yellow 
colour (euchlorine,) and explodes feebly when a hot wire is introduced into 
it, becoming nearly colourless, when the chlorous acid is decomposed. 

Chloric acid, C10 5 . — When a stream of chlorine gas is transmitted through 
a strong solution of caustic potash, the gas is absorbed, and a solution is 
formed which bleaches at first, but loses that property without any escape 
of gas, and becomes a mixture of chloride of potassium and chlorate of potash, 
the latter of which, being the least soluble, separates in shining tabular crys- 
tals. Five equivalents of potash (the oxide of potassium) are decomposed by 
6 of chlorine, 5 of which unite with the potassium and form 5 equivalents of 
chloride of potassium, while the 5 of oxygen form chloric acid with the re- 
maining equivalent of chlorine, as stated in the following diagram: — 



CHLORIC ACID. 267 



ACTION OF CHLORINE UPON POTASH. 

Before decomposition. After decomposition. 

5 Chlorine. . 5 Chlorine 5 Chloride of potassium. 



5 Potassium. 



5 Potash.. J 5 



Chlorine . . . Chlorine _^^ Chloric acid > Chlorate of 

Potash .... Potash . . Potash $ potash. 

Or in symbols: 6 Cl and 6 KO = KO, C10 5 and 5KC1. Stfch is the nature 
of the action of chlorine upon the soluble and highly alkaline metallic oxides. 

The chlorate of barytes may be formed by transmitting chlorine through 
caustic barytes in the same manner; and from a solution of the pure chlorate 
of barytes, chloric acid may be obtained by the cautious addition of sulphuric 
acid, so long as it occasions a precipitate of sulphate of barytes. The solu- 
tion may be evaporated by a very gentle heat till it becomes a sirupy liquid, 
which has no odour, but a very acid taste, is decomposed above 100°, and 
when distilled at a still higher temperature gives water, then a mixture of 
chlorine and oxygen gases, and hyperchloric acid, which may be prepared in 
this way without difficulty. Chloric like nitric acid, is not isolable, being in- 
capable of existing, except in combination with water or a fixed base. This 
acid first reddens litmus paper, but after a time the colour is bleached, and if 
the acid has been highly concentrated, the paper often takes tire. It dissolves 
zinc and iron with disengagement of hydrogen. Chloric acid is decomposed 
by hydrochloric acid, with escape of chlorine, and by most combustible bodies 
and acids of the lower degrees of oxidation, such as sulphurous and phospho- 
rous acids, which oxidate themselves at its expense. 

This acid when free, or in combination, may be recognised by several pro- 
perties. It is not precipitated by chloride of barium or nitrate of silver, and 
has no bleaching power; sulphuric acid causes the disengagement from it of a 
yellow gas, having a peculiar odour, which bleaches strongly; and its salts 
when heated to redness afford oxygen, and deflagrate witli combustibles. 

Chlorates. — This class of salts is remarkable for a general solubility, like 
the nitrates. Those of them which are fusible detonate with extreme violence 
with combustibles. The chlorate of potash, of which the preparation and 
properties will be described under the salts of potash, has become a familiar 
chemical product, being largely consumed in the manufacture of deflagrating 
mixtures. The chlorates were at one time termed hyperoxy muriates, and their 
acid, the existence of which was originally observed by Mr. Chenevix, was 
first obtained in a separate state by Gay-Lussac. 

Hyperchloric acid, C10 7 . — This acid, which is also called perchloric and 
oxichloric acid, is obtained from chlorate of potash in different ways. At that 
particular point of the decomposition of chlorate of potash by heat, when the 
evolution of oxygen is about to become very violent, the fused salt is in a 
pasty state, and contains, as was first observed by Serullas, a considerable 
quantity of hyperchlorate, the oxygen extricated from one portion of chlorate 
being retained by another portion of the same salt. This salt is rubbed to 
powder, and dissolved in boiling water, from which the hyperchlorate is first 
deposited, on cooling, owing to its sparing solubility. The same salt may 
also be prepared by throwing chlorate of potash in fine powder and well dried, 
into oil of vitriol gently heated in an open basin, by a few grains at a time, 
when the liberated chloric acid resolves itself into chlorous acid and hyper- 
chloric acid, the former coming off as a yellow gas; thus: — 



268 CHLORINE. 



RESOLUTION OF CHLORIC ACID INTO CHLOROUS ACID AND HYPER- 

CHLORIC ACID. 

Before decomposition. After decomposition. 

f2 Chlorine ~ _^- ■ 2 Chlorous acid. 

3 Chloric acid J ^Oxygen 
j 7 Oxygen 
L Chlorine - ' — ■ Hyperchloric acid. 

Of the 3 equivalents of potash, previously in combination with the chloric acid, 
one remains with hyperchloric acid as hyperchlorate of potash, and the other 
two are converted into bisulphate of potash. The whole reaction between the 
acid and salt may, therefore, be thus expressed : — 

3(KO, C10 5 ) and 4(HO, S0 3 ) = 2C10 4 and KO, C10 7 
and 2(HO, S0 3 -f KO, S0 3 ) and 2HO. 

In conducting this operation, the greatest caution is necessary, owing to the 
explosive property of chlorous acid ; for if the order of mixing the substances 
be reversed, and the acid poured upon the chlorate, or if too much chlorate be 
added at a time to the acid, a most violent and dangerous detonation may oc- 
cur. But this reaction is chiefly interesting as affording chlorous acid ; for 
hyperchlorate of potash may be obtained from chlorate by the action of nitric 
acid, lately observed by Professor Penny, without danger or inconvenience. 
The chlorate is tranquilly decomposed in nitric acid gently heated upon it, 
the chlorine and oxygen of 3 equivalents of chlorous acid being evolved in a 
state of mixture and not of combination ; the saline residue consists of 3 equiva- 
lents of nitrate and one of hyperchlorate of potash, which may be separated by 
dissolving them in the smallest adequate quantity of boiling water. On cooling, 
the hyperchlorate separates in small shining crystals, which may be dissolved 
a second time to obtain them perfectly pure. 

Hyperchloric acid may be prepared from this salt by boiling it with an excess 
of fluosilicic acid, which forms with potash, a salt nearly insoluble. After cool- 
ing, the clear liquid is decanted and evaporated by a water bath. To eliminate 
a small excess of hydrofluoric acid, a little silica in fine powder is added to the 
liquid, which at a certain degree of concentration carries off the former as fluo- 
silicic acid. After being still further concentrated, the acid liquid may be dis- 
tilled in a retort by a sand-bath heat. A very dilute acid comes over first, but 
the temperature of ebullition rises till it attains 392°, after which the receiver 
should be changed, because what then passes over is a concentrated acid of sp. 
gr. 1.65. This acid is a colourless liquid which fumes slightly in the air. It 
may be still farther concentrated by distilling it with 4 or 5 times its weight of 
strong sulphuric acid, when the greater part of it is decomposed into chlorine 
and oxygen, but a portion condenses in a mass of small crystals, and also in 
long four-sided prismatic needles terminated by dihedral summits, which accord- 
ing to Serullas are two different hydrates of the acid, the last containing least 
water and being most volatile. The crystals and the concentrated solution of 
the acid have a great affinity for water ; the acid itself appears not to be 
isolable. 

The hyperchloric acid is much the most stable of the oxides of chlorine ; it 
does not bleach, is not altered by the presence of sulphuric acid, and is not de- 
composed by sulphurous acid or by sulphuretted hydrogen. It dissolves zinc 
and iron with effervescence, and in point of affinity, is one of the most powerful 
acids. Hyperchloric acid is recognised by producing, with potash, a salt of the 



CHLOROUS ACID. 269 

same sparing solubility as bitartrate of potash. It is an interesting acid from its 
composition, and as being the most accessible of the small class containing 
hyperiodic and hypermanganic acids, to which it belongs. The alkaline hyper- 
chlorates emit much oxygen, when heated, and leave metallic chlorides ; they 
do not deflagrate so powerfully with combustibles as the chlorates. 

Chlorous acid or peroxide of chlorine, C10 4 . — This acid cannot be obtained 
in a state of purity without considerable danger. Gay-Lussac recommends, in 
preparing it to mix chlorate of potash into the state of a paste with sulphuric 
acid previously diluted with half its weight of water and cooled, and to distil the 
mixture in a small retort by a water-bath. It comes off as a gas, of a yellow 
colour considerably deeper than chlorine, which must be collected over mercury. 
It is composed of 2 volumes of chlorine with 4 volumes of oxygen, condensed 
into 4 volumes, which gives it a density of 2337.5. This gas is decomposed 
gradually by light, but between 200° and 212° its elements separate in an in- 
stantaneous manner, with the disengagement of light and a violent explosion 
which breaks the vessels. Water dissolves 7 volumes of this gas, and the gas 
itself may be liquefied by pressure. It bleaches damp litmus paper, without first 
reddening it, and is absorbed by alkaline solutions with the formation according 
to Martens of a peculiar class of decolourizing salts.* These, however, readily 
pass into chlorates and chlorides, like the hypochlorites of Balard, when their 
solutions are heated. 

Chlorous acid has a violent action upon combustibles, kindling phosphorus, 
sulphur, sugar and other combustible substances in contact with which it is 
evolved. Its action upon phosphorus may be shown by 
throwing a drachm or two of crystallized chlorate of pot- 
ash into a deep foot-glass or ale-glass (see figure 84) filled 
with cold water, to the bottom of which the salt falls with- 
out much loss by solution. Oil of vitriol is then conducted 
to the salt, in a small stream, from a tube funnel, the lower 
end of which has been drawn out into a jet with a minute 
opening. A gas of a lively yellow colour is evolved with 
slight concussions, and immediately dissolved by the water, 
to which it imparts the same colour. If while this is occur- 
ring a piece of phosphorus be thrown into the glass, it is ig- 
nited by every bubble of gas, and a brilliant combustion is 
produced under the water, forming a beautiful experiment 
wholly without danger. If a few grains of chlorate of pot- 
ash in fine powder and loaf-sugar, be mixed upon paper by the fingers, (rubbing 
these substances together in a mortar may be attended with a dangerous explo- 
sion,) and a single drop of sulphuric acid be allowed to fall from a glass rod 
upon the mixture, an instantaneous deflagration takes place, occasioned by the 
evolution of the yellow gas which ignites the mixture. Captain Manby used 
to fire in this manner the small piece of ordnance, which he proposed as a life- 
preserver, to throw a rope over a stranded vessel from the shore ; and the same 
mixture was afterwards employed, with sulphuric acid, in various forms of the 
instantaneous light match, all of which, however, are now superseded by other 
mixtures ignited by friction without sulphuric acid. 



OTHER COMPOUNDS OF CHLORINE. 
Chloride of nitrogen, N Cl 3 . — This is one of the most formidable of explosive 




* An. de Ch. et de Ph. t. 61, p. 293. 
23* 



270 



CHLORINE. 



compounds, and great caution is necessary in its preparation, to avoid accidents. 
Four ounces of sal-ammoniac, which must not smell of animal matter, are dis- 
solved in a small quantity of boiling water, filtered, and made up to 3 pounds 
with distilled water ; a two pound bottle of chlorine is inverted in a basin con- 
taining this solution at 90°, being supported by the ring of a retort stand, with 
its mouth over a small leaden saucer. The chlorine gas is absorbed, and upon 
the surface of the liquid, which rises into the bottle, an oily substance condenses, 
which when it accumulates, precipitates in large drops, and is received in the 
leaden saucer. During the whole operation, the bottle must not be approached, 
unless the face is protected by a sheet of wire gauze, and the hands by thick 
woollen gloves ; agitation of the bottle, to make the suspended drop fall, is a 
most common cause of explosion. The leaden saucer, when it contains the 
chloride, may be withdrawn from under the bottle, without disturbing the latter, 
and then no harm can result from the explosion, if it does not occur in contact 
with glass. 

M. Balard finds that this compound may also be produced by suspending a 
mass of sulphate of ammonia in a strong solution of hypochlorous acid. 

The chloride of nitrogen is a volatile oleaginous liquid of a deep yellow colour, 
and sp. gr. 1.653, of which the vapour is irritating like chlorine and attacks the 
eyes. It may be distilled at 160°, but effervesces strongly at 200° and explodes 
between 205° and 212°, producing a very loud detonation, and shattering to 
pieces glass or cast-iron, but producing merely an indentation in a leaden cup. 
It is resolved into chlorine and nitrogen gases, the instantaneous production of 
which with heat and light, is the cause of the violence of the explosion. The 
chloride of nitrogen is decomposed by most organic matters containing hydro- 
gen ; and may be safely exploded by touching it with the point of a cane-rod, 
which has been previously dipped in oil of turpentine. 

The properties of this compound render its accurate analysis almost impos- 
sible, and the correctness of the formula usually assigned to it is very doubtful. 
M. Millon has shown that it may contain hydrogen, and is possibly a com- 
pound of chlorine with amidogen, NH 2 C1. He formed from it corresponding 
compounds, containing bromine, iodine and cyanogen, by double decomposi- 
tion, a bromide, iodide or cyanide of potassium being introduced into the 
chloride of nitrogen for that purpose.* 



CHLORIDES OF CARBON. 

Perchloride of carbon, C 4 C1 6 . — The compounds of these elements are not 
formed directly, but were produced by Mr. Faraday by the action of chlorine 
upon a certain compound of carbon and hydrogen, and the circumstances of 
their formation have been explained lately with singular felicity by M. Regnault. 
Chlorine and oleriant gas C 4 H 4 combine together in equal volumes, and con- 
dense as an oily looking body, of an ethereal odour, which is known as the 
Dutch liquid, from having been first formed by certain associated Dutch che- 
mists, and also as the chloride of olefiant gas, although the latter term is objected 
to as incorrect in theory. Chemists have now agreed, after much discussion, 
that the formula of this liquid is not C 4 H 4 -f-2Cl, but that its elements are thus 
arranged: — 

Dutch liquid C 4 H 3 ,Cl-f-HCl. 

It is a combination of hydrochloric acid IIC1, with the chloride of acetyl 
C 4 H 3 ,C1. Acetyl, or as it is also called aldehydene (C 4 H 3 ) pervades an ex- 



* An. de Ch. et de Ph. t. 69, p. 75. 



CHLORIDES OF CARBON. 271 

tensive series of compounds, aldehydic and acetic acids, for instance, being 
oxides of this radical, namely C 4 H 3 -f-20, and C 4 H 3 -f30; and these com- 
pounds may be traced up to alcohol, the substance from the decomposition of 
which, indeed, this whole class of compounds is primarily derived. Thus 
acetyl with two equivalents of hydrogen forms a higher compound radical 
ethyl C 4 H 3 ,H 2 or C 4 H 5 , of which ether is the oxide, and alcohol the hydrate 
of that oxide. - In both the acetyl and ethyl series, it will be observed that the 
proportion of carbon (C 4 ) is constant, being that originally present in the al- 
cohol, and we shall find it in the chloride of carbon, which is the last product 
of reducing processes upon alcohol. Olefiant gas itself is a hydruret of acetyl 
that is, C 4 H 3 ,H. When exposed to chlorine, both the acetyl and hydrogen 
combine with chlorine, giving the Dutch liquor, C 4 H 3 ,CH-HC1. Comparing 
the formula for olefiant gas with the first part of the last formula, C 4 H 3 ,H with 
C 3 H 3 C1, it will be found that in losing an atom of hydrogen the olefiant gas has 
acquired an atom of chlorine; and this is an instance of the law of substitution 
which Dumas has traced to so great an extent in the formation of organic com- 
pounds. When a stream of chlorine gas is transmitted through the Dutch liquor, 
Regnault finds that another atom of hydrogen is carried off, as hydrochloric acid, 
and an atom of chlorine left in its place; thus the Dutch liquor, C 4 H 3 Cl-f- H 
CI becomes 

C 4 H 2 C1 2 + HC1. 

This second product, which is a liquid, being submitted to the action of a 
stream of chlorine, was found to give rise to a third liquid product, in which 
the hydrochloric acid of the last formula had disappeared, and the remaining 
portion had assumed two additional atoms of chlorine, forming — 

C 4 H 2 C1 4 . 

This third liquid, is changed by the prolonged action of chlorine into the 
perchloride of carbon, but to hasten the action, it is convenient to conduct the 
operation in the light of the sun; its two atoms of hydrogen being carried off 
in the form of hydrochloric acid, and two atoms of chlorine left in their place, 
which gives the formula 

Perchloride of carbon. . . . C 4 C1 6 , or C 4 Cl 4 -fCI 2 . 
Now this view of derivation and constitution of the perchloride of carbon, 
is confirmed by the density of its vapour which Regnault found by experi- 
ment to be 8157. It should from its formula contain 

8 volumes carbon vapour. .... 3371 
12 volumes chlorine 29284 



32655 

If these form a combining measure of 4 volumes, the most usual of all com- 
bining measures, the weight of 1 volume or density of the vapour is 8164, 
which almost coincides with the experimental result.* 

The perchloride of carbon is a volatile crystalline solid, having an aromatic 
odour resembling that of camphor, fusible at 320° and boiling at 360° (Fara- 
day,) of sp. gr. 2, soluble in alcohol ether and oils. It was prepared by Fara- 
day by exposing the Dutch liquid to sunlight in an atmosphere of chlorine, 
which was several times renewed, as the chlorine was absorbed. 

Protochloride of carbon* C 4 C1 4 . — This compound was prepared by Mr. 
Faraday by passing the vapour of the perchloride through a glass tube filled 

* Regnault; De l'Action du Chlore sur la liqueur des Hollandais et sur JeChlorure d'Al- 
dehydene. An. de Ch. et de Ph. t. 69, p. 151. Idem, Sur les Chlorures de Carbon, ib. t. 
70, p. 104. 



272 CHLORINE. 

with fragments of glass, and heated to redness. A great quantity of chlorine 
becomes free, and a colourless liquid is obtained, which when purified from 
perchloride of carbon and chlorine as much as possible, boils at 248° (Reg- 
nault,) has a sp. gr. of 1.5526, and in its chemical relations is very analogous 
to the perchloride of carbon. The density of the vapour of the protochloride 
decides the nature of its constitution. It was found by Regnault to be 5820, 
which corresponds to the composition by volume: — 

8 volumes carbon vapour. . . 3371 
8 volumes chlorine. . . . 19522 



22894 

Density = = 5724. 

4 

It must, therefore, contain 4 atoms of carbon and 4 of chlorine, and its for- 
mula be C 4 C1 4 , or we have come at last to defiant gas C 4 H 4 with its whole 
hydrogen replaced by chlorine. It is interesting to observe how a body re- 
tains, after so many mutations, such distinct traces of its origin. From its 
analysis it might be a compound of single equivalents, CC1, of the simplest 
nature, and so it was considered when named protochloride of carbon, but 
there have been found in it the 4 C of alcohol, to which compound we can 
trace it back, by many steps but with perfect certainty. 

Subchloride of carbon. — Another compound of this class exists, of which 
a specimen produced accidentally was examined by Messrs. Phillips and Fara- 
day. Regnault has formed it, by making the preceding liquid compound pass 
several times through a tube at a bright red heat. It condenses in the coldest 
parts of the tube in very fine silky crystals, which may be taken up by ether, 
and obtained perfectly pure by a second sublimation. The analysis of this 
substance proves that its elements are in the proportion of 2 equivalents of 
carbon to 1 of chlorine, but the number of its equivalents is indeterminate, as 
its density is unknown. If it belongs to the foregoing series, its formula will 
beC 4 Cl 2 . 

Chloro carbonic acid gas, CO, CI. — This gas is made by exposing equal 
measures of chlorine and carbonic oxide to sunshine, when rapid but silent 
combination ensues, and they contract to one half their volume. It is decom- 
posed by water, hydrochloric and carbonic acids being formed, and does not 
combine with bases to form salts. It belongs to the carbonic oxide series. 

Chloride of boron, BC1 3 .— A gaseous compound of these elements was 
obtained by Berzelius, by transmitting chlorine over boron heated in a glass 
tube, and by Dumas by transmitting the same gas over a mixture of boracic 
acid and carbon ignited in a porcelain tube. Its density was found to be 4079 
by Dumas, and it is considered a terchloride. 

Chloride of silicon, Si CI 3 ; — This compound is obtained by similar pro- 
cesses as the last. It is a limpid and volatile liquid, boiling at 124°, and is 
converted by water into hydrochloric acid and silica. 

Chloride of sulphur, S 2 C1. — This compound was first obtained by Dr. 
Thomson in 1804. To prepare it, 2 or 3 ounces of flowers of sulphur may 
be introduced into the body of a tubulated retort and gently warmed. Dry 
chlorine is conducted to the sulphur, by a quill tube descending through a per- 
forated cork in the tubulure of the retort, and a flask may be applied to the 
beak of the retort to receive a small portion of the product which distils over 
during the operation. The chlorine is rapidly absorbed and a dark coloured 
dense liquid is obtained, which boils at about 280°, and has a disagreeable 
odour, somewhat resembling that of sea-weed, but much stronger. Rose finds 
that this is a solution of sulphur in a definite chloride of sulphur S 2 C1, which 



BROMINE. 273 

« 

may be obtained pure by distilling the liquid at a moderate temperature,* 
This compound is capable of dissolving a very large quantity of sulphur, 
which may be obtained in crystals from a solution saturated at a high tempe- 
rature. It is decomposed by water, and hydrochloric and hyposulphurous 
acids formed. 

This compound also absorbs a large but indefinite quantity of chlorine. 
But a definite superior chloride of sulphur has lately been obtained by Rose, 
in combination with several metallic perchlorides.f It is a bichloride of sul- 
phur, SC1 2 , but cannot be obtained in a separate state. When chlorine is 
passed over the bisulphuret of tin, the gas is absorbed, the sulphuret fuses, and 
a compound is formed in yellow crystals, which consists of SnCl 2 -f 2SC1 2 . 
The sulphur of the sulphuret of titanium and of the sulphurets of antimony 
and arsenic is converted by chlorine, in the same manner into bichloride, and 
the metal itself obtains the same proportions of chlorine as it had of sulphur 
previously, the new products also remaining in combination with each other. 

Terchloride of phosphorus, PC1 3 . — This chloride, which corresponds with 
phosphorous acid, is obtained by passing the vapour of phosphorous over cor- 
rosive sublimate in a heated tube; a clear and volatile liquid distils over, of sp. 
gr. 1.45. It is capable of dissolving phosphorus; when mixed with water, it 
is resolved into hydrochloric and phosphorous acids. 

Perchloride of phosphorus, PC1 5 . — Phosphorus takes fire spontaneously 
in a vessel of dry chlorine, and produces a snow white woolly sublimate, 
which is very volatile, rising in vapour below 212°. It is converted by water 
into) hydrochloric and phosphoric acids. Compounds also have been formed 
of chlorine, sulphur and phosphorus by Rose and Serullas, to which Berze- 
lius assigns the speculative formulae SCl 3 -f PC1 2 and PS 6 +2S 3 C1. 



SECTION XI. 

BROMINE. 
Eq. 978.31 or 78.39; Br; density 5393; [~~]~) ' 

This element was discovered by M. Balard of Montpellier in 1826. Its 
name is derived from B/w^os, mal-odour, and was applied to it on account of 
its strong and disagreeable odour. Like the other members of the chlorine 
family, it is found principally in solution, being present in an exceedingly 
minute but appreciable proportion in sea water, under the form of bromide of 
sodium or magnesium, also in the water of the Dead Sea, and in nearly all 
the saline springs of Europe, of which that of Theodorshall near Kreuznach 
in Germany is the principal source of bromine, as an article of commerce. 
Although it has not been found applicable to any important purpose of utility, 
bromine is interesting from its chemical relations, particularly from the extra- 
ordinary parallelism in properties with chlorine which it exhibits. 

Preparation. — Bromine in combination is detected by means of chlorine 
water, a few drops of which cause the colourless solution of a bromide to be- 
come orange yellow, like nitrous acid, by disengaging bromine, while an ex- 
cess of chlorine weakens the indication, by forming a chloride of bromine 
which is nearly colourless. Before the application of this test, the saline 
water in which bromine is contained must always be greatly concentrated, 

* An. de Ch. et de Ph. t. 50, p. 92. 
t An. de Ch. et de Ph. t. 70, p. 278. 



274 BROMINE. 

and, indeed, the greater part of its 1 salts separated by crystallization. The 
bromides are highly soluble and remain in the incrystallizable liquor which is 
called the mother-ley, or bittern in the ca3e of sea-water. The bromide of 
magnesium may lose hydrobromic acid during the farther concentration of the 
mother-ley, by evaporation, on which account Desfosses recommends the ad- 
dition of hydrate of lime to the liquid, which throws down magnesia, and pro- 
duces a bromide of calcium which may be evaporated without loss of bromine. 
Instead of using free chlorine, to extricate the bromine, peroxide of manganese 
and a little hydrochloric acid may be added to the liquid. Upon distilling, 
bromine is liberated and comes off completely before the liquid boils. The 
watery vapour which condenses in the receiver along with the bromine, con- 
tains a portion of chloride of bromine, from which the bromine may be sepa- 
rated by adding barytes to the liquid, and forming a chloride of barium and 
bromate of barytes; evaporating the liquor to dryness, and treating with al- 
cohol. 

Properties. — Bromine condenses in the preceding process as a dense liquid 
under the water, the sp. gr. of bromine being 2.966. In mass, it is opaque 
and of a dark brown red, but in a thin stratum, transparent and of a hyacinth 
red. Its odour is powerful and very like that of chlorine. When cooled 10 
or 15 degrees below zero, it freezes, and remains solid at 10°; it then has a 
leaden gray colour and a lustre almost metallic. Bromine at the usual tempe- 
rature is decidedly volatile, and to retard its evaporation, it is generally covered 
by water in the bottle in which it is kept. It boils at 116°. 5, and affords a 
vapour very similar to the ruddy fumes of peroxide of nitrogen. Bromine is 
soluble to a small extent in water, and gives an orange-coloured solution; it is 
a little more soluble in alcohol, and considerably more so in ether. 

Bromine bleaches like chlorine, and acts in a similar manner upon the vola- 
tile oils and many organic substances containing hydrogen, which element it 
eliminates in the form of hydrobromic acid. Many metals combine with bro- 
mine with ignition, as they do with chlorine; it acts as a caustic on the skin 
and stains it yellow, like nitric acid. It forms a combination with starch, 
which is of a yellow colour; like chlorine it forms a crystalline hydrate with 
water at 32°, which is of a beautiful red tint. 

Hydrobromic acid, H Br. — This is a gas, in which 2 volumes of each 
constituent are united without condensation, as in hydrochloric acid, and which 
has the great attraction for water of that acid. Hydrogen and bromine do not 
unite at the usual temperature, and a mixture of them is not exploded by flame, 
but they unite in contact with the flame and form hydrobromic acid. The 
same acid is more readily prepared by the action of bromine upon certain com- 
pounds of hydrogen, such as sulphuretted hydrogen, phosphuretted hydrogen 
and hydriodic acid. The gas may also be obtained by the mutual action of 
bromine, phosphorus and water, and must be collected over mercury. 

Hydrobromic acid, like all the other bromides, is decomposed by chlorine, 
which is more powerful in its affinities than bromine, but it is not decomposed 
by iodine. Its action with metals is precisely similar to that of hydrochloric 
acid. Hydrobromic acid is not decomposed when heated with oxygen, and 
water is not decomposed by bromine, so that the affinity of bromine and oxy- 
gen for hydrogen may be inferred to be nearly equal. This acid, or a soluble 
bromide, produces white precipitates with the nitrates of silver, lead and sub- 
oxide of mercury, which are very similar to the chlorides of these metals. 
The other metallic bromides correspond in solubility with the chlorides. The 
bromide of silver, like the chloride, is soluble in ammonia. 

Bromic acid, Br 5 . — Bromine is dissolved by the strong alkaline bases, 
and occasions a decomposition exactly similar to that produced by chlorine, in 
which a bromide of the metal and bromate of the metallic oxide are formed. 



IODINE. 275 

The bromic acid may be separated from bromate of barytes by sulphuric acid, 
and its solution may be concentrated to a certain point, like chloric acid, be- 
yond which it undergoes decomposition. It has not been isolated. The 
chief points of difference between chloric and bromic acid are, that the latter 
alone is decomposed by sulphurous and phosphorous acids, and by sulphuret- 
ted hydrogen; and while all the chlorates are soluble, it is said, that the bro- 
mates of silver and suboxide of mercury are insoluble, the former being a 
white and the latter a yellowish white precipitate. Bromic acid is the only 
known oxide of bromine. 

Chloride of bromine, Br Cl s . — Chlorine gas is absorbed by bromine, and a 
volatile fluid of a reddish yellow colour produced. This chloride appears to 
dissolve in water without decomposition, but in an alkaline solution, it is con- 
verted into chloride and bromate. 

Bromide, of sulphur. — Bromine combines when mixed with flowers of 
sulphur, forming a fluid of an oily appearance and reddish tint, much resem- 
bling chloride of sulphur in appearance and properties. This bromide dis- 
solves both sulphur and bromine, and has not been obtained in a state of suffi- 
cient purity for analysis. 

Bromides of phosphorus, P Br 3 and PBr s . — If bromine and phosphorus 
are brought into contact in a flask filled with carbonic acid gas, a violent action 
with ignition takes place, of which the products are a volatile crystalline solid, 
and a yellowish liquid. The former, when decomposed by water, affords 
hydrobromic and phosphoric acids, which proves it to be P Br 5 ; and the lat- 
ter affords hydrochloric and phosphorous acids, which proves it to be P Br 3 . 
The liquid bromide does not freeze at 5°, and like the liquid chloride of phos- 
phorus is capable of dissolving a large quantity of phosphorus. 

Bromide of carbon. — It is probable that the compound described as such by 
Serullas is bromoform, C 2 H Br 3 .* 

Bromide of Silicon — Is prepared by a similar process as the chloride of 
silicon. It is a liquid boiling at 302° and freezing at 10°. By water it is re- 
solved into hydrobromic acid and silica. 



SECTION XII. 

IODINE. 



Eq. 1579.5 or 126.57; I; density 8707.7; j 



Iodine was discovered in 1811, by M. Courtois of Paris, in kelp, a substance 
from which he prepared carbonate of soda. Its chemical properties were ex- 
amined by Clement, and afterwards, more completely by Davy and Gay-Lus- 
sac, particularly the latter.t A trace of iodine has been observed in sea-water 
(Schweitzer,) but it is more abundant in the fuci, ulvi and other marine plants, 
and also in sponge, the ashes of which contain iodide of sodium. It is known 
also to exist in one mineral, a silver ore of Albaradon in Mexico. Iodine has 
not as yet, I believe, found any important application in the useful arts, but it 
has proved a valuable addition to the materia medica. 

Preparation. — The greater part of the iodine of commerce is prepared at 
Glasgow from the kelp of the west coast of Ireland, and western islands of 
Scotland. The sea-weed thrown upon the beach is collected, dried, and after- 

* An. de Ch. et de Ph. t. 39, p. 225. 

X Davy in Philosophical Transactions for 1814 and 1815; Gay-Lussac in the Annalesde 
Chimie, t. 88, 90 and 91. 



276 



IODINE. 



wards burned in a shallow pit, in which the ashes accumulate and melt by the 
heat, being of a fusible material. The fused mass broken into lumps forms 
kelp, which was prepared and chiefly valued at one time for the carbonate of 
soda it contains, which varies in quantity from 2 to 5 per cent. It is not all 
equally rich in iodine. According to the observation of Mr. Whitelaw, the 
long elastic stems of the fucus palmatus afford most of the iodine contained in 
kelp, and the kelp prepared from this plant may be recognised by the presence 
of charred portions of the stems; and as that is a deep sea plant, it is found in 
largest quantity in the sea-wreck of exposed coasts. A high temperature in 
the preparation of the kelp, which increases the proportion of alkaline car- 
bonate, diminishes that of the iodine, owing to the volatility of the iodide of 
sodium at a full red heat. The kelp which contains most iodine, generally 
contains also most chloride of potassium, and it is for these two products that 
the substance is now valued, more than for its alkali. 

The kelp broken into small pieces is lixivated in water, to which it yields 
about half its weight of salts. The solution is evaporated down in an open 
pan, and when concentrated to a certain point, begins to deposite its soda salts, 
namely, common salt, carbonate and sulphate of soda, which are removed 
from the boiling liquor by means of a shovel pierced with holes like a colander. 
The liquid is afterwards run into a shallow pan to cool, in which it deposites a 
crop of crystals of chloride of potassium; the same operations are repeated 
upon the mother-ley of these crystals until it is exhausted. A dense dark-co- 
loured liquid remains, which contains the iodine, in the form, it is believed, of 
iodide of sodium, but mixed with a large quantity of other salts, and this is 
called the iodine ley. 

To this ley, sulphuric acid is gradually added in such quantity as to leave 
the liquid very sour, which causes an evolution of carbonic acid, sulphuretted 
hydrogen, and sulphurous acid gases, with a considerable deposition of sul- 
phur. After standing for a day or two, the ley so prepared, is heated with 
peroxide of manganese, to separate the iodine. This operation is conducted 
p IG g5 in aleaden retort a (see figure) 

of a cylindrical form, sup- 
ported in a sand bath, which 
is heated by a small fire be- 
low. The retort has a large 
opening, to which a capital 
b c, resembling the head of 
an alembic, is adapted, and 
luted with pipe-clay. In the 
capital itself there are two 
openings, a larger and a 
smaller, at b and c, closed 
by leaden stoppers. A series 
of bottles (/, having each two 
openings, connected together 
as represented in the figure, 
and with their joinings luted, 
are used as condensers. The 
prepared ley being heated to 
about 140° in the retort, the 
manganese is then intro- 
duced, and b c luted to a. Iodine immediately begins to come off, and 
proceeds on to the condensers, in which it is collected; the progress of its evo- 
lution is watched by occasionally removing the stopper at c; and additions of 
sulphuric acid or manganese are made by b, if deemed necessary. The sue- 




IODINE. 277 

cess of the experiment depends much upon its being slowly conducted, and 
upon the proper management of the temperature, which is more easily regu- 
lated when the quantities of materials are considerable, than when the experi- 
ment is attempted with small quantities in glass flasks. In the latter circum- 
stances, chlorine is often evolved with the iodine, which escapes in acrid fumes, 
as the chloride of iodine, and is lost; but this accident can be avoided in the 
manufacturing process. A little cyanide of iodine often accompanies the 
iodine, which being more volatile, condenses in the form of white, flexible, 
prismatic crystals, in the bottle most distant from the leaden retort. 

In this operation, the peroxide of manganese will be in contact at once 
with hydriodic, hydrochloric and sulphuric acids; and the iodine of the hy- 
driodic acid may be liberated, from the union of its hydrogen with the oxygen 
of the manganese, and the formation of water; or hydrochloric acid may be 
first decomposed by the manganese, and chlorine decompose the hydriodic 
acid and liberate iodine. If a considerable excess of sulphuric acid be em- 
ployed, iodine is obtained without the use of the peroxide of manganese, the 
oxygen required by the hydrogen of the hydriodic acid being supplied by the. 
sulphuric acid, a part of which is converted into sulphurous acid. The pre- 
sence of iodine in the prepared ley may be observed by suddenly mixing it 
with an equal volume of oil of vitriol, when violet fumes of iodine appear. 
But the quantity of iodine may be more accurately estimated by means of a 
solution consisting of 1 part of crystallized sulphate of copper and §| cr. pro- 
tosulphate of iron, which throws down an insoluble subiodide of copper, al- 
most white. 

Properties. — Iodine is generally in crystalline scales of a bluish black colour 
and metallic lustre. It may also be obtained, from solution, in the form of 
elongated octahedrons with a rhomboidal base. The density of iodine is 4.948; 
it fuses at 225°, and boils at 347°; but it evaporates at the usual temperature, 
and more rapidly when damp than when dry, diffusing an odour having con- 
siderable resemblance to chlorine, but easily distinguished from it. Iodine 
stains the skin of a yellow colour, which however disappears in a few hours. 
Its vapour is of a splendid violet colour, which is seen to great advantage when 
a scruple or two of iodine is thrown at once upon a hot brick. Hence its 
name, from 'I*^, violet-coloured. The vapour of iodine is the heaviest of 
gaseous bodies, its density being 8716 according to the experiment of Dumas, 
and 8707.7 according to calculation from its atomic weight 

Pure water dissolves about l-7G00th of its weight of iodine, and acquires a 
brown colour; but when charged with a salt, particularly the nitric or hydro- 
chlorate of ammonia, water dissolves a considerably greater quantity of iodine. 
The solution of iodine does not disengage oxygen in the light of the sun, and 
does not destroy vegetable colours, but after a time it becomes colourless, and 
then contains hydriodic and iodic acids. In other respects, iodine generally 
comports itself like chlorine, but its affinities are much less powerful. Iodine 
is soluble in alcohol and ether, with which it forms dark reddish brown liquors. 
Solutions of iodides, too, all dissolve much iodine. A liquid containing 20 
grains of iodine and 30 grains of iodide of potassium in 1 ounce of water, is 
known as Lugol's solution, and preferred to the tincture in medicine, because 
the iodine is not precipitated from it by dilution with water. 

A solution of starch forms an insoluble compound with iodine, of a deep 
blue colour, the production of w r hich is an exceedingly delicate test of iodine. 
If the iodine be free, starch produces at once the blue precipitate, but if it be 
in combination as a soluble iodide, no change takes place, till chlorine is added 
to liberate the iodine. If more chlorine, however, be added than is necessary 
for that purpose, the iodine is withdrawn from the starch, chloride of iodine 
24 



278 IODINE. 

formed, and the blue compound destroyed. Dr. A. T. Thomson, after adding 
the starch with a drop of sulphuric acid to the liquid containing an iodide, in a 
cylindrical vessel, allows the vapour only from the chlorine- water bottle to fall 
upon the solution, and not the chlorine-water itself. In this way, the danger 
of adding an excess of chlorine is easily avoided, and the test indicates in a 
sensible manner an exceedingly minute quantity of iodine. The iodide of 
starch, in water, becomes colourless when heated, but recovers its blue co- 
lour if immediately cooled. The soluble iodides give, with nitrate of silver, 
an insoluble iodide of silver, of a pale yellow colour, insoluble in ammonia; 
with salts of lead, an iodide of a rich yellow colour, and with corrosive subli- 
mate, a fine scarlet iodide of mercury. 

In ascertaining the quantity of iodine in the mixed chlorides, and iodides of 
mineral waters and other solutions, Rose recommends the addition of nitrate of 
silver, which throws down a mixture of chloride and iodide of silver, which is 
fused and weighed. This is afterwards heated in a tube and chlorine passed 
over it, by which the iodine is expelled, and the whole becomes chloride of sil- 
ver. It is weighed again, and a loss is found to have occurred, owing to the equiv- 
alent of the replacing chlorine being less than that of the replaced iodine. This loss, 
multiplied by 1.389, gives the quantity of iodine originally present, which has 
been expelled by the chlorine.* Dr. Schweitzer employs a similar method in 
estimating the quantity of iodine when mixed with bromine, heating the iodide 
and bromide of silver in an atmosphere of bromine. The difference in weight 
multiplied by 2.627 gives the proportion of iodine, and multiplied by 1.627 the 
proportion of bromine, f 

Uses. — Iodine is employed in the laboratory for many chemical preparations, 
and as a test of starch. It was first introduced into medicine by Coindet of 
Geneva, who employed it with success, in the treatment of goitre, dissolved in 
alcohol, in solution of iodide of potassium, or as iodide of sodium ; and since 
that application, most mineral waters to which the virtue of curing goitre was 
ascribed, have been found to contain iodine. M. Boussingault has adduced 
striking confirmations of the efficacy of iodine in that disease, in his interesting 
memoir on the iodiferous mineral waters of the Andes.J It appears to have a 
specific action in causing the absorption of glandular swellings, and is also ad- 
ministered as a tonic. Iodine swallowed in the solid state may cause ulceration 
of the mucous membrane of the stomach and death. But the iodide of potas- 
sium or sodium is not poisonous in large doses, nor is the iodide of starch hurt- 
ful (Dr. A. Buchanan.) 

Iodides. — Iodine does not form a hydrate like chlorine, but it combines with 
another compound body, ammonia; dry iodine absorbing dry ammoniacal gas 
and running into a brown liquid, which Bineau finds to contain 20.4 ammonia 
for 100 iodine, quantities in the proportion of 3 equivalents of ammonia to 2 of 
iodine. § This liquid dissolves iodine. Iodine does not combine with dry iodide 
of potassium, but with the addition of a small quantity of water, it forms what 
appears to .be a ternary compound of iodide of potassium, water and iodine, 
which is fluid, but was obtained in crystals by Bauer. It forms similar combi- 
nations with other hydrated metallic iodides. With the metals generally iodine 
combines, with the same facility, and nearly with as much energy as chlorine 
does. The iodide of zinc and protiodide of iron, which are very soluble, are 
formed by simply bringing the metals into contact with iodine, in water. All 
the iodides are decomposed by bromine, as well as by chlorine. 



* Handbuch der analytischen Chemie von Heinrich Rose, B. 2, p. 577, Berlin, 1838. 

■j- Phi). Mag. 3rd. series, v. 15, p. 57. 

I An. de Ch. et de Ph. t. 54, p. 163. § An. de Ch. et de Ph. t. 67, p. 226. 



HYDRIODIC ACID. 279 

The compounds of iodine may be shortly described in the following order : 



Hydriodic acid . H I 

Iodic acid . . . 10, 

Hyperiodic acid . I 7 

Iodide of Nitrogen N I, 



Iodide of sulphur. 
Iodides of phosphorus. 
Chlorides of iodine. 
Bromides of iodine. 



COMPOUNDS OF IODINE. 

Hydriodic add, H I. — Hydriodic acid cannot be prepared with advantage by 
treating the iodide of sodium or potassium with hydrated sulphuric acid, as the 
latter is partially converted into sulphurous acid by hydriodic acid, with the 
separation of iodine. It may be obtained in the state of gas, by forming an 
iodide of phosphorus, 9 parts of dry iodine and 1 of phosphorus being introduced 
into a tube sealed at one end, to be used as a retort, and the mixture covered 
by pounded glass, and combination determined by a gentle heat ; and after- 
wards decomposing this iodide of phosphorus by a few drops of water. Hydri- 
odic acid instantly comes off as gas, and hydrated phosphorous acid remains in 
the tube. Or PI 3 and 6H O = ~3H I and 3H + P0 3 . A slight heat may be 
applied to the tube, when the action abates, to expel the last portions of hydri- 
odic acid ; but if the temperature be elevated, the residuary hydrated phospho- 
rous acid is decomposed with the evolution of phosphuretted hydrogen gas, 
which may, therefore, be obtained by the same operation. This gas is very 
soluble in water, and soon decomposed over mercury, which combines with its 
iodine and liberates hydrogen, so that it ought to be collected by the method of 
displacement. The gas is conducted by a tube to the bottom of a dry bottle, the 
air of which it displaces, as in the experiment with hydrochloric acid (fig. 80. 
page 257,) and the bottle is closed with a glass stopper when full of gas. 
Hydriodic gas is colourless, of density 4443 by experiment and 4385 by 
theory, and consists of 2 volumes of iodine vapour and 2 volumes of hydrogen 
gas united without condensation, or forming 4 volumes, which are, therefore, 
the combining measure of the gas. In the combination of its constituents by 
volume, hydriodic acid resembles hydrochloric gas and all the other hydrogen 
acids. Hydriodic gas is gradually decomposed by oxygen, with the formatiojn 
of water ; iodine is liberated. 

The solution of this acid in water may be obtained by transmitting sul- 
phuretted hydrogen gas through water in which iodine is suspended ; the iodine 
combines with the hydrogen of that compound and liberates the sulphur. The 
liquid may afterwards be warmed to expel the excess of sulphuretted hydrogen, 
and filtered. It is colourless at first, but in a few hours becomes red, owing to 
the decomposition of hydriodic acid by the oxygen of the air, and the solution 
of the iodine in the acid. The solution has its maximum boiling point, which 
lies between 257° and 262°, when of sp. gr. 1.7, according to Gay-Lussac. 
Nitric and sulphuric acids decompose it, and are decomposed themselves, 
with the formation of water ; the starch test then indicates free iodine. 

Lniir ad:!, 10 5 . — Iodine does not afford a peculiar acid compound, with red 
oxide of mercury and those metallic oxides which yield hypochlorous acid with 
chlorine. Nor is it absorbed, like chlorine, by hydrate of lime or alkaline so- 
lutions, to form a class of bleaching salts. Such compounds are wanting in the 
series of oxides of iodine, which is at present limited to iodic and hyperiodic 
acids. Sementini imagined that he had formed inferior oxides of iodine, but he 
is evidently mistaken. The iodate of soda combines with iodide of sodium in 
several proportions, one of which was supposed by Mitscherlich, when he dis- 



280 IODINE. 

covered it, to be an iodite of soda, but that this is a double salt of the consti- 
tution first mentioned is now beyond doubt. 

A few grains of iodic acid may easily be prepared by the method of Mr. Con- 
nel, which consists in heating the most concentrated nitric acid upon a little 
iodine, in a wide glass tube, and afterwards evaporating to dryness by a heat 
not exceeding 4 or 500° ; a white crystalline powder remains in the tube, 
which is anhydrous iodic acid. When a larger quantity is required, the most 
convenient process is to form, in the first place, an iodate of soda. An ounce 
or two of iodine may be suspended in a pound of water, with occasional agi- 
tation, and a stream of chlorine be passed through, till the whole iodine is dis- 
solved. Carbonate of soda is added to the liquor, which is of a brown colour 
and strongly acid till it becomes slightly alkaline, when a large precipitation of 
iodine occurs, which may be separated and collected on a filter. This iodine 
may be suspended in water and exposed to a stream of chlorine as before. 
But the filtered solution contains iodate of soda and chloride of sodium, with a 
trace of carbonate, which may be neutralized by hydrochloric acid. On after- 
wards adding chloride of barium to the filtered solution, so long as a precipitate 
is produced, the whole iodic acid will be thrown down as iodate of barytes, 
which may be collected on a filter and dried. This iodate is anhydrous, and 
may be decomposed completely, by boiling 9 parts of it for half an hour with 2 
parts of oil of vitriol, diluted with 10 or 12 parts of water. The liberated iodic 
acid dissolves, and being separated from the sulphate of barytes by filtration, is 
obtained as an anhydrous crystalline mass when evaporated to dryness by a 
gentle heat. 

Iodic acid crystallizes from a strong solution, as a hydrate, in large and trans- 
parent crystals, which are six-sided tables. This acid is not sublimed, but de- 
composed, by a high temperature, and leaves no solid residue. Iodic acid is 
very soluble and after reddening bleaches litmus paper. It oxidates all metals 
with which it has been tried, except gold and platinum. It is deoxidized by 
sulphurous acid, and iodine liberated, but an excess of sulphurous acid causes 
the iodine again to disappear as hydriodic acid, water being decomposed by the 
simultaneous action of sulphurous acid and iodine upon its elements. Morphia 
is said to be the only vegetable alkali which decomposes iodic acid and liberates 
iodine ; and, hence, iodic acid has been recommended as a test for morphia. 

Iodates. — The salts of iodic acid have a general resemblance to the chlorates. 
The iodate of potash is converted by heat into iodide of potassium and oxygen ; 
but the iodate of soda loses iodine as well as oxygen, when heated, and a yellow, 
sparingly soluble, alkaline matter remains, which Liebig imagines to contain the 
salt of an iodous acid, resolvable into an iodate and iodide by solution in water, 
but which requires further investigation. The iodates of metallic protoxides, 
with the exception of the potash family, are all sparingly soluble or insoluble 
salts. The iodate of lime contains water, and when heated affords no iodide of 
calcium, but caustic lime. 

Fixed acids, which have little affinity for water, such as iodic acid, appear 
often to combine in several proportions with oxides of the potash family. The 
ordinary biniodate of potash contains, I find, an atom of basic water, but at a 
high temperature it is made anhydrous, and then a salt remains containing two 
atoms of acid to one of potash. Mr. Penny has crystallized a biniodate and 
teriodate of soda, both anhydrous. 

Iodic acid likewise combines with other acids, an observation, of Davy's, 
which was disputed, but has been confirmed by Berzelius * These are com- 
pounds which generally precipitate in a crystalline form, when another acid is 
added to a hot and concentrated solution of iodic acid. Compounds of sulphuric, 

* Traite de Chimie, t. I. p. 212. 



IODIDES. 281 

nitric, phosphoric and boracic acids with iodic acid were formed by Berzelius. . 
The compound with sulphuric acid may be sublimed without decomposition. 
When vegetable acids are dissolved in iodic acid, they are immediately decom- 
posed by it, carbonic acid being disengaged with effervescence and iodine pre- 
cipitated 

Hyperiodic or Periodic acid, I 7 . — This acid, which was discovered by 
Magnus and Ammermuller, is formed by transmitting a current of chlorine 
through a solution of iodate of soda, to which, at least, three times as much 
caustic soda has been added as there is of soda in the iodate. Two salts are 
formed, the chloride of sodium and a hyperiodate of soda with excess of soda, 
which is sparingly soluble, and precipitated by nitrate of silver, which throws 
down a sub-hyperiodate of silver. This salt may be washed, and afterwards 
dissolved in nitric acid, and the solution evaporated yields orange-yellow crystals 
of neutral hyperiodate of silver. It is remarkable that when these crystals are 
thrown into water they are decomposed, the whole oxide of silver precipitating 
with half the hyperiodic acid, as the former insoluble sub-hyperiodate, while 
half the acid is dissolved by the water without a trace of silver, and obtained in 
a state of purity. This solution when evaporated affords hyperiodic acid in 
crystals, which are unalterable in the air, and of which the solution in water is 
not changed by ebullition. The solution, treated with hydrochloric acid, affords 
chlorine and iodic acid, water being formed. Hyperiodic acid is resolved into 
oxygen and iodine by a high temperature. 

b'uperiodates. — Besides neutral salts of this acid, subsalts of the potash family 
exist which contain two of base to one of acid. If these are subsalts they are 
unique, as no true subsalts of the potash family are known. But it is more 
probable that hyperiodic acid forms a second and bibasic class of salts, to which 
they belong* 

Iodide of nitrogen. — Iodine has* an action similar to that of chlorine upon 
ammonia, and forms when digested in a solution of that substance, an insoluble 
black powder, which is powerfully detonating, and analogous to the chloride of 
nitrogen. The iodide detonates more easily, but less violently than the chloride, 
always exploding spontaneously when it dries. Another process is to mix a 
great excess of ammonia, with a saturated solution of iodine in alcohol, and 
afterwards to add water so long as iodide of nitrogen precipitates. The filter 
with the humid precipitate should be divided into several pieces, otherwise the 
whole may explode, at once, upon drying. The same obscurity hangs over 
the composition and constitution of the iodide as the chloride of nitrogen. 

When caustic soda is added to the solution of iodine in alcohol or wood-spirit, 
a yellow substance of a saffron odour precipitates, which was supposed by Mits- 
cherlich to be the periodide of carbon, but is iodoform, of which the formula is 
C 2 HI 3 . No true iodide of carbon is known. 

Iodide of sulphur. — This compound is formed by fusing together 4 parts of 
iodine and one of sulphur. It has a radiated crystalline structure, but its ele- 
ments are easily disunited, the iodine escaping entirely from this compound 
when it is left exposed in the air. 

Iodides of phosphorus. — Iodine appears to combine with phosphorus in several 
proportions, when they are brought in contact and slightly heated. In all these 
combinations, the mass becomes hot without inflaming, if the phosphorus is not 
at the same time in contact with air. One part of phosphorus with 6, 12 and 
20 parts of iodine forms fusible solids, which may be sublimed without change, 
but which are decomposed by water, all of them yielding hydriodic acid, and 
the first affording besides phosphorus and phosphorous acid, the second phos- 
phorous acid, and the third phosphoric acid. 



* Poggendorff's Annalen, vol. 28, p. 514. 
24* 



2S2 FLUORINE. 

Chlorides of iodine.— Chlorine is readily absorbed by dry iodine and perhaps 
more than one compound formed. Berzelius forms a definite compound by 
distilling a mixture of 1 part of iodine with 4 parts or more of chlorate of potash. 
There is formed in the retort, a mixture of iodate and hyperchlorate of potash, 
at the same time that oxygen gas is disengaged, and a chloride of iodine is 
formed which condenses in the receiver. This chloride of iodine is a yellow or 
reddish liquid, of an oily consistency, of a sharp and peculiar odour, and of a 
taste which is feebly acid, but very astringent and rough. It is soluble in water 
and alcohol ; and ether extracts it from its aqueous solution unaltered, so that 
it is not decomposed by solution in water. It is supposed to consist of single 
equivalents of chlorine and iodine * 

When iodine is completely saturated with chlorine, it forms a compound which 
is solid and yellow, fusible by heat, but which cannot be sublimed without loss 
of chlorine. It fumes in air and has an acrid odour. It is decomposed by water 
and forms a colourless solution, which consists of hydrochloric and iodic acids. 
This proves the composition of this iodide to be I Cl 5 . When treated in the 
dry state with anhydrous alcohol or ether, these menstrua take up hydrochloric 
acid and chloride of iodine, leaving iodic acid white and pulverulent. 

Bromides of iodine. — Iodine likewise forms two bromides, which are both 
soluble in water. The solution bleaches litmus paper without first reddening it. 



SECTION XIII. 

FLUORINE. 

Eq. 233.8 or 18.74; F; density {hypothetical) 1292; 



This elementary body is most frequently found in the mineral kingdom in 
combination with calcium, as fluoride of calcium, which constitutes the mineral, 
fluor spar, and exists in small quantity in amphibole, mica and most of the 
natural phosphates ; a trace of it also occurs in the enamel of the teeth, and in 
the bones of animals. Of all bodies, fluorine appears to possess the most power- 
ful and general affinities, and to be, therefore, the most difficult to isolate, or to 
preserve for the study of its properties. Indeed we have hitherto learned little 
more of fluorine than that it exists and may be isolated. Several of its com- 
pounds, however, are of less difficult preparation and well known. 

Sir H. Davy made several attempts to isolate fluorine. He exposed the 
fluoride of silver in a glass tube to gaseous chlorine, at a high temperature, and 
found that chloride of silver was produced, and fluorine therefore liberated, but 
it was absorbed and replaced by oxygen, which it disengaged from the silica 
and soda of the glass. When Davy repeated the same experiment in a platinum 
vessel, the metal became covered with fluoride of platinum. He proposed after- 
wards to construct vessels of fluor spar for the reception of the fluorine, which 
he expected to disengage from the fluoride of phosphorus by burning it in oxygen 
gas; but he does not appear to have carried this project into execution, and it 
is to be feared that any such operation, in which an excess of chlorine is 
necessarily employed, would yield a chloride of fluorine, rather than pure fluo- 
rine. M. Baudrimont avoided the use of chlorine, and transmitted the volatile 
fluoride of boron over deutoxide of lead (minium) in an ignited porcelain tube. 
Having obtained a gas, supposed to be fluorine, which did not act upon glass, 
mixed with much oxygen, he substituted for this, another operation quite anala- 

* Berzelius, Traite de Chimie, 1. 1, p. 110. 



HYDROFLUORIC ACID. 283 

gous to the usual process for chlorine. Oil of vitriol was heated upon a mixture 
of fluor spar and peroxide of manganese, in a glass retort. The gaseous pro- 
duct was believed to be a mixture of hydrofluoric and fluosilicic acids with 
fluorine vapour, which were not separated from each other, but the latter is 
described as a gas of a yellowish brown colour, having an odour resembling 
chlorine and burnt sugar, and capable of bleaching. Fluorine did not act upon 
glass, but combined at once with gold. The Messrs. Knox have obtained similar 
results * But more than one skilful chemist of name has been less fortunate in 
obtaining indications so decisive of the isolation of fluorine. 

Hydrofluoric acid, HF. — Schwankhardt, of Nuremberg, observed in 1670, 
that it was possible to etch upon glass by means of fluor spar and sulphuric 
acid, but it was not till 1771 that Scheele referred this action to a particular 
acid which sulphuric acid disengaged from fluor spar. Wenzel first obtained 
the true hydrofluoric acid, exempt from silica, by preparing it in proper me- 
tallic vessels, the acid collected by Scheele being the fluosilicic and not the 
hydrofluoric. The preparation and properties of the pure acid were more 
fully studied by Gay-Lussac and Thenard in 1810. It was then known as 
fluoric acid, and was supposed, according to the doctrine of the day, to con- 
tain oxygen. The idea of its being a hydrogen acid was first suggested, a 
few years afterwards, by M. Ampere, whose views in theoretical chemistry 
were often marked by much acuteness and originality. The view of Ampere 
is now generally assented to, although from our imperfect knowledge of fluo- 
rine, the constitution of hydrofluoric acid does not rest upon the same indis- 
putable evidence as that of hydrochloric acid, to which it is assimilated. 

Preparation. — To obtain hydrofluoric acid anhydrous, a specimen of fluor 
spar is selected free from siliceous minerals and galena; this is reduced to an 
impalpable powder and distilled by a gentle heat in a retort of lead, with twice 
its weight of highly concentrated oil of vitriol. The materials become viscid 
and swell considerably, and an acid vapour distils over, which is even more 
acrid and suffocating than chlorine, and produces severe sores if allowed to 
condense upon the hands of the operator. This vapour is received in a flask 
or bottle, likewise of lead, kept cold by ice, in which it condenses without the 
presence of water. The acid, thus obtained, may be preserved in vessels of 
platinum or gold, provided with stoppers of the same metal which fit accu- 
rately, or in vessels of lead formed without tin solder, tin being rapidly acted 
upon by hydrofluoric acid. If the solution of this acid in water is required, 
the extremity of the leaden tube, from the retort, may be allowed to touch the 
surface of water in a platinum crucible or capsule, by which the acid vapour 
is readily condensed; and the dilute acid may be preserved without much con- 
tamination in a glass bottle, which has been previously heated and coated in- 
ternally with melted bees-wax. 

Fluor spar, which is employed in this operation, is the fluoride of calcium, 
upon which the action of hydrated sulphuric acid is similar to its action upon 
chloride of sodium, in which hydrochloric acid is produced. Water is de- 
composed, by the hydrogen and oxygen of which, the fluorine and calcium 
are converted respectively into hydrofluoric acid and lime; and the former 
comes off as vapour, while the latter remains in the retort as sulphate of lime. 
In symbols: 

CaF and HO, S0 3 = HF and CaO, S0 3 . 

Water is, therefore, necessary to the formation of hydrofluoric acid in the pro- 
cess given for its preparation; and the observation of M. Kuhlman, that anhy- 

* Baudrimont, Phil. Mag. 3rd series, v. 10, p. 149; G. J. and the Rev. T. Knox, lb. vols 
9, p. 107 and 12, 105. 



284 FLUORINE. 

drous sulphuric acid vapour has no action upon fluor spar at a high tempera- 
ture, is readily accounted for. Did fluor spar contain an oxygen acid, in com- 
bination with lime, the acid should be equally liberated by the anhydrous or 
hydrated sulphuric acid. 

Properties. — Anhydrous hydrofluoric acid is a colourless, fuming and very 
volatile liquid, boiling not much above 60°; and which does not freeze at 4°. 
Its sp. gr., which is 1.0609, is increased to 1.25 by the addition of a certain 
quantity of water, for which it has an intense affinity. Hydrofluoric like hy- 
drochloric acid, dissolves the more oxidable metals with the evolution of hy- 
drogen gas. Mixed with nitric acid, it dissolves ignited silicon and titanium, 
with disengagement of nitric oxide; but that acid mixture has no action upon 
the noble metals, such as gold and platinum, which are dissolved by aqua regia. 
Several insoluble acid bodies, which are not acted on by sulphuric, nitric or 
hydrochloric acid, are dissolved with facility by hydrofluoric acid; such as 
silica, titanic, tantalic, molybclic and tungstic acids. Water is then formed 
from the oxygen of these acids and the hydrogen of hydrofluoric acid, and 
fluorides of silicon or of the metals of the acids enumerated are likewise pro- 
duced; which fluorides appear to combine with undecom posed hydrofluoric 
acid, when water is present. This acid destroys glass by acting upon its 
silica. If a drop of the concentrated acid be allowed to fall upon a glass plate, 
it becomes hot, enters into ebullition and volatilizes in a thick smoke, leaving 
the spot with which it was in contact deeply corroded, and covered by a white 
powder composed of the elements of the glass excepting a portion of the silica, 
"which has passed off as gaseous fluoride of silicon. 

The diluted solution, or the vapour of hydrofluoric acid is sometimes used to 
etch upon glass. The purity of the acid being of little moment in this applica- 
tion of it, the sulphuric acid and fluor spar may be mixed in a stone ware eva- 
porating basin.. The glass is warmed sufficiently to melt bees' wax rubbed 
upon it, and thereby covered with a coating of that substance, which is after- 
wards removed from the parts to be etched, by a pointed rod of lead or tin, 
employed as a graver. A gentle heat being applied to the basin, acid fumes 
are evolved to which the etched surface of the glass is exposed for a minute or 
two, care being taken not to melt the wax. The wax is afterwards removed 
by warming the glass, and wiping it with tow and a little oil of turpentine, 
when the exposed lines are found engraved to a depth proportional to the time 
they have been exposed to the acid fumes. But in taking impressions upon 
paper from glass plates engraved in this way, as from a copper-plate, they are 
too apt to be broken from the pressure applied in printing. 

To detect the minute quantity of hydrofluoric acid, which exists in many 
minerals, Berzelius recommends that the substance to be examined be reduced 
to fine powder and mixed with concentrated sulphuric acid, in a platinum cru- 
cible covered by a small plate of glass, waxed and engraved as described. 
The crucible is then exposed to a gentle heat, insufficient to melt the wax, and 
in half an hour, the glass plate may be removed and cleaned. If the mineral 
submitted to the test contained fluorine, the design will be perceived upon the 
glass ; when the quantity of fluorine, however, is very small, tl^e engraving does 
not appear immediately, but becomes visible on passing the breath over the 
glass. The presence of silica in the mineral interferes with this operation, but 
an indication may then be obtained by heating a fragment of the mineral to 
redness upon a piece of platinum foil slipped into a glass tube, 8 or 10 inches in 
length and open at both ends. The tube is held obliquely with the mineral 
near the lower end, and so that part of the vapour from the flame passes up the 
tube. The moisture, thus introduced, carries away the gaseous fluoride of 
silicon, and condenses in drops in the upper part of the tube. These drops 
when afterwards evaporated, in drying the tube, leave a white spot, which con- 



FLUOSILICIC ACID. 



2S5 



sists of silica, coming from the decomposition of the fluoride of silicon by the 
water with which it condensed (Berzelius.) Dr. G. O. Rees has lately called 
in question the existence of fluorine in bones, which he finds, contrary to the 
general opinion, not to be indicated in them by this test. 

Fluoride of boron, fluoboric acid, BF 3 . — This compound is gaseous, and is 
obtained when dry boracic acid is brought in contact with concentrated hydro- 
fluoric acid; when boracic acid is ignited with fluor spar; and most conve- 
niently by heating together in a glass retort, 1 part of vitrefied boracic acid, 2 
of fluor spar, and 12 of concentrated sulphuric acid, although this process does 
not give it free from fluosilicic acid. The reaction by which the fluoboric acid 
is then produced may be thus expressed : 

aCaF and B0 3 and 3(HO,S0 3 ) = 3(CaO,S0 3 ) and 3HO and BF 3 . 

Fluoboric gas has no action upon glass, and may be collected in glass vessels 
over mercury. It is colourless, but produces thick fumes when allowed to 
escape into the atmosphere. Its density according to Dr. J. Davy is 2371, and 
2312 according to Dumas, who finds 1 volume of this gas to contain I5 vol. of 
fluorine. Fluoboric gas is not decomposed by iron and the ordinary metals, 
even at a bright red heat, but on the contrary, potassium, with the metals of 
the alkalies and alkaline earths, decompos.es it at a red heat ; boron is liberated 
by potassium, and a double fluoride of boron and potassium also formed. Wa- 
ter absorbs fluoboric acid gas with the greatest avidity, taking up, according 
to J. Davy, 700 times its volume, which increases its bulk considerably and 
raises its density to 1.77. The most ready mode of preparing the solution of 
this acid, is to dissolve crystallized boracic acid in hydrofluoric acid. The acid 
is extremely caustic and corrosive, charring and destroying wood and organic 
matters, when concentrated, like sulphuric acid, probably from its avidity for 
moisture. 

A dilute solution of fluoride of boron, undergoes spontaneous decomposition, 
according to Berzelius, depositing one fourth of its boron in the form of boracic 
acid, which crystallizes at a low temperature ; while a compound of hydroflu- 
oric acid and fluoride of boron remains in solution, which he terms hydrofluo- 
boric acid. The fluoride of boron has a great disposition to form double fluo- 
rides, and acts upon basic metallic oxides like the following compound. 

Fluoride of silicon, fluosilicic. acid, Si F v — This gas is obtained in the follow- 
ing manner : equal parts of fluor spar and broken glass or quartzy sand, in fine 
powder, are mixed in a glass flask a (figure 86,) 
to be used as a retort, with six parts of concen- 
trated sulphuric acid, and stirred well together. 
A disengagement of gas immediately takes 
place and the mass swells up considerably, so 
that the flask must be capacious. After a time a 
gentle heat is required to aid the operation. Flu- 
osilicic gas is collected over mercury. In its 
physical characters it resembles fluoboric gas. 
Its density is 3574 according to J. Davy, and 
3600 according to Dumas ; it contains twice 
its volume of fluorine. In transmitting this gas 
into water, the tube must not dip in "the fluid, 
for it would speedily be choked by the deposition 
of silica, produced by the action of water upon 
the gas. In the arrangement figured, the ex- 
tremity of the exit tube is covered by a small column of mercury m, in the lower 
part of the jar, through which the gas passes before it reaches the water wi 
Every bubble of gas exhibits a remarkable phenomenon, as it enters the water, 



Fig. 86. 




286 FLUORINE. 

becoming invested with a white bag of silica, which rises to the surface. It of- 
ten happens, in the course of the operation, that the gas forms tubes of silica, in 
the water through which it gains the surface without decomposition, if they are 
not broken from time to time. When water is completely saturated with the 
fluoride of silicon, it has taken up about once and a half its weight, and is 
a gelatinous, semi-transparent mass, which fumes in the air. The liquid con- 
tains two equivalents of water to one of the original fluoride of silicon ; but one- 
third of the fluoride has been decomposed by the water and converted into 
hydrofluoric acid and silica. The hydrofluoric acid and fluoride of silicon, in 
solution, are supposed to be in combination by Berzelius, forming 3HF-f 2SiF 3 , 
which is termed by him hydrofluo silicic acid. When this liquid is placed in a 
moderately warm situation, the whole of it gradually evaporates, the free hydro- 
fluoric acid reacting upon the deposited silica, with formation of water; and 
fluoride of silicon is revived. 

The most remarkable property of the fluoride of silicon is to produce, with 
neutral salts of potash, soda and lithia, precipitates which are gelatinous, and so 
transparent, as to be scarcely visible at first in the liquor, and with salts of 
barytes, a white and crystalline precipitate which appears in a few seconds. 
Almost all the basic metallic oxides decompose this acid, when they are em- 
ployed in excess ; separating silica, and giving rise to metallic fluorides. When, 
on the other hand, no more of the base is applied than the quantity required to 
neutralize the free hydrofluoric acid, combinations are obtained with all bases, 
which are analogous to double salts ; consisting of a metallic fluoride combined 
with fluoride of silicon, the proportion of the latter containing twice as much 
fluorine as the former. The formula of one of these compounds, the double 
fluoride of silicon and potassium, is2Si F 3 -f 3KF, and those of other metals are 
similar. The ratio of 2 to 3, in the equivalents of the two fluorides which form 
these double salts, is unusual. 

Dr. Clark, to whose judgment on the subject of atomic weights I would great- 
ly defer, considers that the equivalent number of silicon adopted by Berzelius 
is too high by one-third; and should be reduced from 277.31 to 184.87. With 
this change, silica comes to consist of 1 eq. of silicon and 2 of oxygen, or is 
analogous to carbonic acid ; and the fluoride of silicon, of 1 of silicon and 2 of 
fluorine. The double fluorides, in question, may then be represented by single 
equivalents of fluoride of silicon and metallic fluoride ; fluoride of silicon and 
potassium, for instance, by Si F 2 -j-KF; and the hydrofluosilicic acid of Ber- 
zelius, by Si F 2 -fH F. Dr. Clark connects with this an interesting speculation 
respecting the constitution of these salts, which he would assimilate to the ferro- 
cyanide of potassium, considered as a compound of ferrocyanogen and potas- 
sium, Cy 5 Fe4 2K. The fluoride of silicon and potassium may be viewed in 
the same way, as a compound of a salt-radical containing the silicon and all the 
fluorine of the salt, with potassium ; that is, SiF s -f-K; a view which accounts 
for some salts of this class not being decomposed by potash, and which is 
favoured by the increasing number of classes of salts, which appear to be formed 
on a similar type. 

No combination of fluorine with oxygen is known, nor of fluorine with ni- 
trogen or carbon. 

Fluorides of sulphur and of phosphorus were formed by Davy, by distilling 
the fluoride of lead or of mercury with sulphur or phosphorus, in platinum ves- 
sels. There result a sulphuret or phosphuret of the metal, and a fluoride of 
sulphur or of phosphorus, which volatillizes. Both of these compounds present 
themselves as fuming liquids. The fluoride of phosphorus is decomposed by 
water, hydrofluoric acid with phosphorous acid being formed ; it is, therefore, a 
terfluoride of phosphorus, PF 3 . This fluoride is capable of taking fire and 
burning in air, when it is presumed that phosphoric acid is produced, and 
gaseous fluorine set free, which diffuses itself in the atmosphere. 



HYDROGEN AND SULPHUR. 287 



CHAPTER If. 

COMPOUNDS OF HYDROGEN. 

SECTION I. 

HYDROGEN AND SULPHUR. 

Sulphuretted hydrogen, or hydrosulphuric acid, Eq. 213.67 or 17.12; SH; 
density 1177; Q^J* 



Certain compounds of hydrogen with the non-metallic elements have been 
reserved for separate consideration, which could not be introduced with advan- 
tage at an earlier period : namely, the compounds of hydrogen with sulphur 
and selenium with nitrogen and phosphorus, and with carbon. With sulphur, 
hydrogen forms at least two compounds, one of which, sulphuretted hydrogen 
gas, is a reagent of frequent application and considerable importance. 
. Preparation. — Of those metals which dissolve in dilute sulphuric acid, with 
the displacement of hydrogen, the protosulphurets dissolve also in the same acid, 
but the hydrogen then evolved carries off sulphur in combination and appears 
as sulphuretted hydrogen gas. The protosulphuret of iron, which is commonly 
employed in this operation, is obtained by depriving yellow pyrites or bisulphu- 
ret of iron of a portion of its sulphur by ignition in a covered crucible ; or 
formed directly by exposing to a low red heat a mixture of 4 parts of coarse 
sulphur and 7 of iron filings or borings in a covered stone-ware or cast-iron 
crucible. The sulphuret of iron, thus obtained, is broken into lumps, and acted 
upon by diluted sulphuric acid in a gas-bottle, exactly as zinc is treated in the 
preparation of hydrogen gas (page 195.) Sulphuretted hydrogen is evolved 
without the application of heat, and should be collected over water at 80 or 90° ; 
or if collected in a gasometer or gas holder, the latter may be filled with brine, 
in which this gas is less soluble than in pure water. Sulphuretted hydrogen 
obtained by this process, generally contains free hydrogen, arising from an in- 
termixture of metallic iron with the sulphuret. The gas may also be evolved 
from the action of hydrochloric acid upon the sulphuret of iron, but as it is then 
impregnated with the vapour of the acid, and may also, like every gas produced 
with effervescence, carry over drops of fluid, it should always be transmitted 
through water, before being applied to any purpose as pure gas. The reaction 
by which sulphuretted hydrogen is usually evolved, is expressed in the follow- 
ing equation : 

FeS and HO, S0 3 = HS and FeO, S0 3 . 

Sulphuretted hydrogen, without any admixture of free hydrogen, is obtained 
by digesting in a flask, used as a retort, with a gentle heat, sulphuret of anti- 
mony in fine powder with concentrated hydrochloric acid, in the proportion of 
1 ounce of the former to 4 ounce measures of the latter. The gas of this ope- 



288 COMPOUNDS OF HYDROGEN. 

ration, after being passed through water and dried, may be considered as pure. 
It may be collected over mercury, but is gradually decomposed by that metal, 
which has a strong affinity for sulphur, and hydrogen is liberated, without any 
change of volume. The reaction between hydrochloric acid and sulphuret of 
antimony may be thus expressed : 

3H CI and Sb S 3 = 3HS and Sb Cl 3 . 

Properties. — Sulphuretted hydrogen is a colourless gas, of a strong and very 
disagreeable odour. Its density is 1191.2, by the experiments of Gay-Lussac 
and Thenard. It consists of 2 volumes of hydrogen and l-3rd vol. of sulphur 
vapour, condensed into 2 vols., which form its combining measure. By a pres- 
sure of 17 atmospheres at 50°, it is condensed into a highly limpid, colourless 
liquid, of sp. gr. 0.9, which is of peculiar interest as the analogue of water in 
the sulphur series of compounds. The solvent powers of this liquid have not 
been examined. The air of a chamber slightly impregnated by this gas may 
be respired without injury, but a small quantity of the undiluted gas inspired 
occasions syncope, and its respiration, in a very moderate proportion, was found 
by Thenard to prove fatal — birds perishing in air containg 1-1 500th, and a dog, 
in air containing 1 -800th part of this gas. Water dissolves, at 64°, 2J volumes 
of this gas, and alcohol, 6 volumes. These solutions soon become milky, when 
exposed to air, the oxygen of which combines with the hydrogen of the gas, 
and precipitates the sulphur. Those mineral waters termed sulphureous, con- 
tain this gas, although rarely in a proportion exceeding 1£ per cent, of their 
volume. They are easily recognised by their odour, and by blackening silver. 
Sulphuretted hydrogen is highly combustible, and burns with a pale blue 
flame, producing water and sulphurous acid, and generally a deposite of sulphur 
when oxygen is not present in excess. A little strong nitric acid thrown into a 
bottle of this gas, occasions the immediate oxidation of its hydrogen, and often 
a slight explosion with flame, when the escape of the vapour is impeded by 
closing the mouth of the bottle by the finger. Sulphuretted hydrogen is im- 
mediately decomposed by chlorine, bromine and iodine, which assume its hy- 
drogen ; the odour of sulphuretted hydrogen in a room is soon destroyed, on 
diffusing a little chlorine through it. Tin and many other metals, heated in this 
gas, combine with its sulphur with flame, and liberate an equal volume of hy- 
drogen. Potassium decomposes one moiety of the gas in that manner, and be- 
comes sulphuret of potassium, which unites with the other moiety without de- 
composition, forming a hydrosulphuret of the sulphuret of potassium. The 
action of other alkaline metals upon sulphuretted hydrogen is similar. 

This compound has a weak acid reaction, and is generally classed with the 
hydrogen acids. It does not combine and form salts with basic oxides, but it 
unites with basic sulphurets, such as sulphuret of potassium, and forms com- 
pounds which are strictly comparable with hydrated oxides. When sulphu- 
retted hydrogen is passed over lime at a red heat, both compounds are decom- 
posed, and water with sulphuret of calcium is formed. The oxides of nearly 
all the metallic salts, whether dry or in a state of solution, are decomposed by 
sulphuretted hydrogen in a similar manner. But in those salts, of which the 
metallic sulphurets are dissolved by acids, such as salts of iron, zinc and man- 
ganese, a small quantity of a strong acid entirely prevents precipitation. These 
sulphurets are generally coloured, and many of them are black ; hence, the effect 
of sulphuretted hydrogen in blackening salts of lead and silver, which renders 
these compounds so sensitive as tests of the presence of that substance. Sul- 
phuretted hydrogen also tarnishes certain metals, such as gold, silver and brass, 
so that utensils of which these metals are the basis should not be exposed to this 
gas. 

Per sulphuret of hydrogen. — When carbonate of potash is fused with half its 



HYDROGEN AND SELENIUM. 2S9 

weight of sulphur, a sulphuret of potassium is formed containing a large excess 
of sulphur, which affords a solution in water of an orange red colour. The 
protosulphuret of potassium, with hydrochloric acid, gives sulphuretted hydro- 
gen and chloride of potassium : H CI and K S = H S and K CI. But when 
the red solution of persulphuret of potassium is poured in a small stream, into 
hydrochloric acid, diluted with two or three volumes of water, while chloride of 
potassium is formed as before, the sulphuretted hydrogen produced combines 
with the excess of sulphur present, and forms a yellowish oily fluid, the persul- 
phuret of hydrogen, which falls to the bottom of the acid liquor. The result of 
the combination in this case appears rather capricious ; for if the acid and per- 
sulphuret of potassium be mixed in the other way, — if the acid be added drop 
by drop to the alkaline sulphuret,-then sulphuretted hydrogen gas is evolved, the 
whole excess of sulphur precipitates, and no persulphuret of hydrogen is formed. 
The oily fluid produced by the first mode of mixing has considerable analogy 
in its properties to the peroxide of hydrogen, and appears, like that compound, 
to have a certain degree of stability imparted to it by contact with acids, while 
the presence of alkaline bodies on the contrary, give its elements a tendency to 
separate. 

Thenard has observed other points of analogy between these compounds. 
Like peroxide of hydrogen, the persulphuret produces a white spot upon the 
skin. The latter compound is also resolved into sulphuretted hydrogen and sul- 
phur by all the bodies which effect the transformation of the former into water 
and oxygen, such as charcoal powder, platinum, iridium, gold, peroxide of man- 
ganese, and the oxides of gold and silver, which when the persulphuret is dropt 
upon them, are decomposed in an instant and even with ignition. The persul- 
phuret of hydrogen undergoes spontaneously the same decomposition, even in 
well closed bottles, which are apt, on that account, to be broken. It is soluble 
in ether, but the solution soon deposites crystals of sulphur. Thenard finds 
this body not to be uniform in its composition, the proportion of sulphur often 
exceeding considerably 2 proportions to 1 of hydrogen. The oily fluid may, 
therefore, be sometimes one and sometimes another compound of sulphur and 
hydrogen.* 



SECTION II. 

HYDROGEN AND SELENIUM. 

Selenietled hydrogen, H Se. — One compound of these elements is known, 
which is obtained by processes similar to those already described, and possesses 
considerable analogy to sulphuretted hydrogen. It is a colourless gas, soluble 
in water, and readily decomposed by the conjoint action of water and air, with 
precipitation of selenium. All metallic solutions, even those of zinc and iron, 
when neutral, are precipitated by solution of selenietted hydrogen, and the me- 
tallic seleniets are generally black or dark brown, with the exception of those of 
zinc, manganese and cerium, which have a flesh colour. The odour of this 
gas is exactly similar to that of sulphuretted hydrogen, but it was found, by 
Berzelius, to exercise so violent an action upon the respiratory organs, as to 
make the inspiration of it, even in a highly diluted state, a most painful and 
even dangerous experiment (Traite, I. 340.) 

* An. de Ch. et de Ph. t. 48, p. 79. 
25 



290 COMPOUNDS OF HYDROGEN 

t 

SECTION IIL 

HYDROGEN AND NITROGEN, 

AMIDOGEN. 

Eq. 202 or 16.9; NH 2 or Ad ; not isolable. 

Hydrogen and nitrogen do not combine directly, but three compounds of 
these elements are generally admitted to exist, only one of which, however, 
ammonia, can be obtained in a separate state. It is even highly probable that 
amidogen is the only direct combination of these elements, and that the other 
two are compounds of amidogen with hydrogen. These compounds are — 

Amidogen . . . NH 2 .... NH 2 
Ammonia . . . NH^-fH . . . NH 3 
Ammonium . . . NH2-J-2H . . . NH 4 

Judging from the nature of the combinations in which amidogen is found, it 
appears to be a compound of the salt-radical class, in which it occupies a low 
place, superior to oxygen, but considerably inferior to chlorine, or perhaps even 
sulphur. The white precipitate of pharmacy, formed on adding ammonia to a 
solution of chloride of mercury, is a body in which amidogen was proved to 
exist by the analysis of Dr. Kane, which has been repeated and confirmed by 
Ullgren. The term amide being applied to combinations of amidogen,and the 
sy mbol Ad assigned to it, white precipitate is a compound of chloride of mer- 
cury with amide of mercury, and is expressed by HgCl-f-HgAd. Dr. Kane 
has also shown that the black compound obtained on washing calomel or sub- 
choride of mercury with ammonia, is a corresponding combination of subchlo- 
ride with subamide of mercury, Hg 2 Cl 4- Hg 2 Ad; and he has ascertained the 
existence of amidogen in a variety of other mercurial compounds. But it is to 
be observed of the metallic combinations of amidogen, that those which have 
been certainly established are confined to that metal, and also that amides of 
mercury have never been obtained in a separate state, but always in combina- 
tion with another mercurial salt. The idea was thrown out by Dumas, that 
the explosive compounds of nitrogen might contain amidogen, and the same 
view has been applied to the fulminating compounds produced by the action of 
ammonia upon the oxides of silver and gold ; but these views have not yet been 
fully verified by analysis. 

Potassium, heated in ammoniacal gas, NH 3 , disengages hydrogen, as when 
it acts upon water. If ammonia were then simply reduced to the state of ami- 
dogen, 4 volumes of the former should be decomposed to evolve 2 volumes of 
hydrogen; but in the numerous experiments of Gay-Lussac and Thenard, 
never more than 3£ volumes of ammonia were required to furnish 2 volumes 
of hydrogen, and consequently a small portion of the hydrogen must be fur- 
nished by the decomposition of amidogen itself. The compound of potassium, 
which is a fusible solid matter of an olive-green colour, likewise contains urn- 
decomposed ammonia. The basis of it is, probably, a compound of potas- 
sium and amidogen, but its constitution is very problematical. Ever since the 
formation of this compound, by Davy and the chemists named above, the ex- 
istence of such a body as amidogen has been a floating speculation among 



HYDROGEN AND NITROGEN. 291 

chemists. Bat it was first fixed and distinctly enunciated by Dumas, in his 
theory of the amides, in reference to a class of compounds of which he is the 
discoverer. 

Oxamide, NH 2 ,C 2 2 . — When oxalate of ammonia is decomposed by heat, 
a white insoluble sublimate is obtained, which was termed oxamide by Dumas, 
and viewed as a combination of amidogen and carbonic oxide, NH 2 ,C 2 2 ; 
being formed by the abstraction of the elements of two atoms of water from 
oxalate of ammonia, of which the formula is NH 4 0, C 2 3 ^ When oxamide 
is boiled with an alkali or with an acid, the two atoms of water are again 
assumed, and oxalic acid with ammonia reproduced. Similar amides may be 
formed from other organic acids. 

Sulphamide, NH 2 ,S0 2 . — This is a compound exactly analogous to oxa- 
mide, containing the radical sulphurous acid, S0 2 , instead of C 2 2 , in com- 
bination with amidogen. Sulphamide was formed, by Regnault, by the action 
of dry ammonia upon chlorosulphuric acid, when 2 equivalents of ammonia 
and 1 of chlorosulphuric acid become sulphamide and hydrochlorate of am- 
monia: 

2NH, and S0 2 ,C1 = NH 2 ,S0 2 and NH 4V Cl. 

M. Regnault did not succeed completely in separating sulphamide from the. 
hydrochlorate of ammonia; these bodies are nearly equally soluble, both in 
water and alcohol, and separate very imperfectly by crystallization. Sulpha- 
mide has a great attraction for moisture, and quickly deliquesces in the air, in 
which respect it differs completely from the product NH 3 ,S0 3 , resulting from 
the combination of anhydrous sulphuric acid with dry ammoniacal gas, and 
which some chemists have viewed as a hydrated sulphamide, NH o ,S0„ -f HO. 
The solution of sulphamide, in water, does not undergo any "spontaneous 
change; a solution even acidulated with hydrochloric acid and mixed with 
chloride of barium, in a close vessel, was not sensibly disturbed by the for- 
mation of sulphate of barytes in the course of a month. But at the boiling 
point, sulphamide changes slowly into the ordinary sulphate of ammonia by 
the fixation of the elements of water; and the presence of a strong acid facili- 
tates that transformation. 

Carbamide, NH 2 ,CO. — Chlorocarbonic gas (page 272) condenses ammo- 
niacal gas, forming a compound which has hitherto been viewed as a chloro- 
rarbonate of ammonia, 2NH 3 -f CO,Cl, but which M. Regnault finds to be a 
mixture of carbamide and hydrochlorate of ammonia, NH 2 ,CO and NH 4 , 
CI. This compound is not deliquescent, dissolves easily in water and in 
alcohol slightly diluted. Carbamide is not decomposed by acetic or oxalic 
acid, nor by the strongest acids if diluted, but concentrated* nitric acid occa- 
sions the evolution of carbonic acid. Its solution is not disturbed by chloride 
of barium. The elements of urea, N 2 H 4 ,C 2 0,, are the same as those of 
carbamide, but the equivalent of the former, inferred from its capacity of satu- 
ration as an organic base, is double that of the latter." 



AMMONIA. 
Eq. 214.54 or 17.19; NH 3 or HAd; density 591.5; 



Ammonia is a volatile alkali, which derives its name from sal-ammoniac, a 
salt from which it is generally extracted, and which received its title from 



* Regnault, An. de Ch. et de Ph. t. 69, p. 180. 



292 COMPOUNDS OF HYDROGEN. 

being first prepared in the district of Ammonia, in Libya. It is produced in 
the destructive distillation of all organic matters containing nitrogen, which 
has given rise to one of its popular names, the spirits of hartshorn. It is also 
produced during the putrefaction of the same matters in the atmosphere. In 
the mineral kingdom, it appears often to be formed in oxidation, when effected 
by the simultaneous action of air and water, as in the rusting of iron, and a 
trace of it is always found in the native oxides of iron, in the varieties of clay, 
and in some other minerals. 

Preparation.— -In a state of purity, ammonia is a gas, of which the liquor 
or aqua ammonise is a solution in water. This solution, which is of constant 
use as a re-agent, is prepared by mixing intimately sal-ammoniac (hydrochio- 
rate of ammonia) with an equal weight of slaked lime, and distilling the mix- 
ture in a glass retort, by the diffused heat of a chauffer or sand-pot. Ammo- 
niacal gas comqs off, which should be passed through a small quantity of 
water, to arrest a little dust of lime that is carried along with it, and afterwards 
be conducted into a quantity of distilled water, to condense it, equal to the 
weight of the salt employed. Chloride of calcium and the excess of lime re- 
main in the retort, and a considerable quantity of water is liberated in the pro- 
cess, and distils over with the ammonia. This important re-action is explained 
in the following diagram: 



PROCESS FOR AMMONIA. 

Before decomposition. After decomposition. 

669 Hvdrochlorate f Ammonia 214| 214* Ammonia. 

nf^mmnni* 1 Hydrogen 12*. 

^Chlorine 442 s/\. 

C Oxygen . 100 ^^^^ 112£ Water. 

? Calcium . 256 ^, 698 Chloride of 



of ammonia 
356 Lime 



calcium. 



1025 1025 1025 

Or iri symbols: NH 4 ,C1 and CaO == NH 3 and HO and CaCl. 

To obtain ammoniacal gas, the solution prepared by the preceding process 
may be boiled by a gentle heat, when the gas is first expelled from its superior 
volatility; or the gas may be derived at once from sal-ammoniac, mixed with 
twice its weight of quicklime in a small retort, and collected over mercury. 

Properties. — Ammonia is a colourless gas, of a strong and pungent odour, 
familiar in spirits of hartshorn. It is composed of 2 volumes of nitrogen and 
6 of hydrogen, condensed into 4 vols., which form the combining measure of 
this gas. Ammonia is resolved into its constituent gases, in these proportions, 
when transmitted through an ignited porcelain tube containing iron or copper 
wire, while the metal, at the same time, becomes brittle, and is supposed by 
Despretz to absorb nitrogen, although this is doubtful. By a pressure of 6.5 
atmospheres, at 50°, it is condensed into a transparent colourless liquid, of 
which the sp. gr. is about 0.76. Ammoniacal gas is inflammable in air in a 
low degree, burning in contact with the flame of a taper. A mixture of this 
gas with an equal volume of nitrous oxide may be detonated by the electric 
spark, and affords water and nitrogen. Water is capable of dissolving several 
hundred times its volume of ammoniacal gas, and the solution is always spe- 
cifically lighter, and has a lower boiling point than pure water. According to 
the observations of Davy, solutions of sp. gr. 0.872, 0.9054 and 0.9692 con- 
tain respectively 32.5, 25.37 and 9.5 per cent, of ammonia. Ammoniacal 
gas is also largely soluble in alcohol. 



HYDROGEN AND NITROGEN. 293 

Solution of ammonia has an acrid alkaline taste, and produces blisters on 
the tongue and skin. When cooled slowly to — 40°, it crystallizes in long 
needles of a silky lustre. The solution has a temporary action upon turmeric 
paper, which it causes to be brown while humid; it also restores the blue 
colour of litmus reddened by an acid, changes the blue colour of the infusion 
of red cabbage into green, and neutralizes the strongest acids, properties which 
it possesses in common with the fixed alkalies. When ammonia is free, it 
may always be detected by its odour, by forming dense, white fumes with 
hydrochloric acid, and by forming a deep blue solution with salts of copper. 

Ammonia, in solution, is decomposed by chlorine, with the evolution of 
nitrogen gas and formation of hydrochlorate of ammonia; when ammonia and 
chlorine, both in the state of gas, are mixed together, the action that ensues 
is attended with flame. Dry iodine absorbs ammoniacal gas, and forms a 
brown viscous liquid (page 278,) which water decomposes, dissolving out 
hydriodate of ammonia, and leaving a black powder, which is the explosive 
iodide of nitrogert. 

The consideration of ammonia, as a compound of amidogen and hydrogen, 
was involved in the explanation given by Dumas of the formation of oxamide 
and other amides; but ammonia was first fully studied under this point of view 
by Dr. Kane, in his elaborate and valuable paper on the compounds of ammo- 
nia lately published.^ He has there successfully illustrated the nature of the 
two following classes of ammoniacal compounds, namely, those of ammonia 
with dry acids, and with anhydrous salts. 

Ammonia and anhydrous oxygen acids. — Ammoniacal gas is condensed by 
dry carbonic acid gas, sulphurous acid, anhydrous sulphuric acid, &c, and 
saline compounds are formed which are not to be confounded with the ordinary 
salts of ammonia, these containing ammonium. The class of salts in question 
has been minutely studied by Rose.f Ammonia, or the amide of hydrogen 
being viewed by Dr. Kane as a weak base, like water or the oxide of hydrogen, 
these salts are compared by him with hydrated acids or salts of water. They 
are the true salts of ammonia as a base. 

With carbonic acid ammonia combines only in the proportion of single 
equivalents, or 4 vols, of ammoniacal gas with 2 vols, of carbonic acid. This 
carbonate of ammonia is a light, white, very volatile powder, of a strong ammo- 
niacal odour, in the vapour of which the constituent gases are united without 
condensation. The density of this vapour is, therefore, 902. This compound 
exists in, and is the cause of the strong odour of the smelling salts, or carbonate 
of ammonia of the shops. By water it is decomposed, and resolved into free 
ammonia and the bicarbonate of the oxide of ammonium. 

With sulphurous acid gas, ammonia condenses in two proportions : namely, 
4 vols, of ammonia with 2 and 4 vols, of sulphurous acid, forming a neutral 
sulphite and a bisulphite of ammonia. The neutral salt attaches itself to the 
sides of the vessel in which the gases are mixed as a solid crust, or in feathery 
crystals of a reddish yellow colour. It rapidly absorbs moisture from the air, 
becomes white, and changes into the neutral sulphite of the oxide of ammonium. 

With anhydrous sulphuric acid, ammonia appears also to form two combi- 
nations, only one of which, however, the neutral sulphate of ammonia, has been 
obtained in a definite state. This salt appears to dissolve in water without de- 
composition, and neither of its constituents is immediately affected or fully pre- 

* Transactions of the Royal Irish Academy, vol. 19, pt. I. 

t On the combinations of Ammonia with Carbonic Acid j Taylor's Scientific Memoirs, 
vol.2, p. 98: 

Sur le Sulfate anhydre d'Ammoniaque, An. de Ch. et de Ph. t. 62, p. 389. 
Sur le Sulfite anhydre d'Ammoniaque, lb. p. 407. 

25* 



294 COMPOUNDS OF HYDROGEN. 

cipitated by the reagents which usually have that effect. Thus chloride of 
strontium and chloride of calcium do not disturb its solution for several hours ; 
chloride of platinum precipitates, at first, only a small portion of the ammonia, 
and chloride of barium, a small portion of the sulphuric acid of the salt. By 
boiling, its solution is gradually, but never completely converted into the ordinary 
sulphate of the oxide of ammonium, and this conversion seems always to precede 
the action of the reagents mentioned upon it. But, as Dr. Kane remarks, this 
sulphate of ammonia contains, on the binary theory of salts, a peculiar salt-radical, 
S0 3 NH 2 , and not S0 4 united with H ; so that its salt-radical is not necessarily 
precipitated in the same circumstances as the salt-radical of a sulphate. 

Ammonia with anhydrous salts. — Ammoniacal gas is absorbed by many 
anhydrous salts, and easily expelled from several of them again by heat. These 
combinations have also been most fully examined by Rose.* In many of them, 
the ammonia appears to discharge a function analogous to that of water of 
crystallization in salts, a function which is in accordance with its constitution as 
an amide of hydrogen. The salt generally rises in temperature during the ab- 
sorption of the gas, and forms a bulky light powder. Sulphate of manganese 
absorbs 2 equivalents of ammonia, sulphate of zinc 2£, sulphate of copper 2|, 
sulphate of nickel 3 equivalents, sulphate of cobalt and sulphate of cadmium also 
3, sulphate of silver I equivalent, nitrate of silver absorbs 3 equivalents, chloride 
of calcium and chloride of strontium absorb 4 equivalents, chloride of copper 3, 
chloride of cobalt 2, chloride of lead fths of an equivalent, chloride of silver Is, 
subchloride of mercury and chloride of mercury \ eq., iodide of mercury 1 eq. 
In some of these salts, the ammonia is more intimately combined than in others ; 
the compound of chloride of mercury with ammonia, for instance, may be sub- 
limed without decomposition, while the compound with iodide of mercury loses 
all its ammonia by exposure to the air ; and in some salts, one portion of 
ammonia is retained more strongly than the rest ; this I found to be the case 
with half an equivalent in several of the sulphates, and with a whole equivalent 
in several of the chlorides of the magnesian family. 

Ammoniated salts, closely related to the preceding, are often obtained on 
transmitting ammoniacal gas through a strong solution of such salts as, in the 
dry state, combine with ammonia. Nitrate of silver crystallizes with two atoms 
of ammonia (G. Mitscherlich ;) nitrate of copper, with two also,, and no water 
(Kane;) sulphate of copper, with two ammonia and one water; chlorides of 
copper and zinc, with the same (Kane.) 



AMMONIUM. 

Eq. 226.96 or 18.19; NH 4 or H 2 Ad; not isolable. 

A compound radical consisting of ammonia with an additional atom of hydro- 
gen, was first supposed to exist in the ordinary salts of ammonia by Berzelius, 
and termed ammonium. This body has never been insulated, but is supposed 
to appear, in a certain experiment, in combination with mercury, and possessed 
of the metallic character (page 143.) It is not necessary, however, that ammo- 
nium be a metal to be admitted as a basyle, and its existence is now generally 
rested upon evidence of a different nature. The compounds of ammonium are- 
always strictly isornorphous with the corresponding compounds of potassium. 

Chloride of ammonium, hydrochlorate or muriate of ammonia, sal-ammo- 
niac, NH 4 ,C1. — This salt is formed when ammonia is neutralized by hydro- 
chloric acid ; NH 3 and HC1 = NH 4 ,C1. It is prepared in large quantity from 



* An de Ch. et de Ph. t. 62, p.. 308. 



HYDROGEN AND NITROGEN. 295 

the ammoniacal liquor obtained in the distillation of bones, in the manufacture 
of animal charcoal, and from the liquor which condenses in the distillation of 
coal for gas. These liquors contain ammonia principally in the state of car- 
bonate and hydrosulphuret, which may be converted into chloride of ammonium 
by the addition of hydrochloric acid. The salt is purified by crystallization, 
and sublimed in vessels of iron or earthenware, in the upper part of which it 
condenses and forms a solid cake, the condition in which sal-ammoniac is 
always met with in commerce. 

Sal-ammoniac is tenacious and difficult to reduce to powder; its sp. gr. is 1.45, 
It has a sharp and acrid taste, and dissolves in 2.72 parts of cold, and in an 
equal weight of boiling water ; it is also soluble in alcohol. It generally crys- 
tallizes from solution in feathery crystals, which are formed of rows of minute 
octohedrons attached by their extremities. 

A corresponding bromide, iodide and fluoride of ammonium may be formed 
by neutralizing ammonia with hydrobromic, hydriodic and hydrofluoric acids. 

Sulphurefs of ammonium. — When 4 volumes of ammonia combine with 2 
of sulphuretted hydrogen, the suJphuret of ammonium is produced; NH 3 and 
HS = NH 4 ,S.. Ammonium combines with sulphur in several other proportions, 
which are obtained on mixing and distilling the various degrees of sulphuration 
of potassium with sal-ammoniac. In the reciprocal decomposition which occurs, 
the potassium combines simply with chlorine, and the ammonium with sulphur. 
The following compounds are generally enumerated: NH 4 ,S; NH 4 ,S-fHS; 
NH 4 ,S 3 and NH 4 ,S 5 . The protosulphuret has long been formed by distilling 
a mixture of quicklime, sulphur and sal-ammoniac, and known under the name 
of the fuming liquor of Boyle. It is a volatile liquid, the vapour of which is 
decomposed by oxygen, and thus fumes are produced. The second compound, 
which is a hydrosulphuret of the sulphuret of ammonium, is formed by trans- 
mitting sulphuretted hydrogen through solution of ammonia to saturation. This 
liquid is generally called the hydrosulphuret of ammonia, and is the form in 
which sulphuretted hydrogen is most frequently used as a reagent. All the 
sulphurets of ammonium are soluble in water and alcohol without decomposition. 
Nitrate of ammonium, NH 4 0, N0 5 .— When nitric acid is saturated with 
ammonia, a salt is obtained which crystallizes in six-sided prisms, and is iso- 
morphous with nitrate of potash. Besides the elements of nitric acid and am- 
monia, this salt contains an atom of water which cannot be separated from it, 
which is also found in, and is equally essential to the salts formed by neutralizing 
all other oxygen acids by ammonia, such as sulphurous acid, sulphuric, carbonic, 
&c., in contact with water. The hydrogen of this water is assigned to the 
ammonia, to form ammonium, which the oxygen converts into oxide of ammo- 
nium; so that the product is nitrate of the oxide of ammonium; or NH 3 and 
HO, N0 5 = NH 4 0, N0 5 . This salt deflagrates with flame, when thrown upon 
red hot coals. When decomposed between 3 and 400°, it is resolved into water 
and nitrous oxide (page 211.) 

Carbonates of ammonium. — The neutral carbonate of oxide of ammonium 
appears not to exist in a free state, but by distilling the sesquicarbonate of am- 
monia of the shops, by a gentle heat, Rose obtained a volatile crystalline 
salt, which may be viewed as a compound of carbonate of ammonia with car- 
bonate of ammonium: NH 3 ,C0 2 + NH 4 0,C0 2 . When the commercial 
salt is exposed to the air, it loses its pungent odour, and a white friable mass 
remains, which is the bicarbonate of ammonium, or carbonate of water and 
oxide of ammonium: H0,C0 2 -f-NH 4 O,C0 2 . This is a stable salt, and 
may be dissolved and crystallized without change. 

The sesquicarbonate of ammonia of the shops is a crystalline transparent 
mass, which Rose finds to have generally, but not always, the composition 
assigned to it by Mr. Phillips, or to contain 3CO a with 2NH 3 and 2HO. 



296 COMPOUNDS OF HYDROGEN. 

Rose is disposed to consider it a compound of carbonate of ammonia and bi- 
carbonate of oxide of ammonium, or NH 3 C0 2 -f (HO, C0 2 -{-NH 4 0,C0 2k ) 
Mr. Scanlan has shown that a small quantity of water dissolves out the carbo- 
nate from this salt, and leaves the bicarbonate, which is the, least soluble. 
This observation does not prove the commercial salt to be a mechanical mix- 
ture of the two salts derived from it, as many undoubted compounds of two 
salts are decomposed by water, when one of the constituent salts is much 
more soluble than the other. Another salt was obtained by Rose, in well 
formed crystals, of which the ammonia and carbonic acid are in the proportions 
of the sesquicarbonate, but with three additional atoms of water. No less than 
twelve different carbonates of ammonia are described by that chemist, (Scien- 
tific Memoirs, ii, 98.) 

Sulphate of ammonium, NH 4 0,S0 3 +HO. — This is a highly soluble salt, 
which possesses an atom of water of crystallization, in addition to the atom 
which is essential to its constitution. The salt may be deprived of the former 
by a gentle heat. 

It is to be observed that salts of this class are still generally named as salts 
of ammonia, although admitted to contain ammonium. 

Compounds of ammonia and metallic salts, supposed to resemble the ammo- 
nium compounds. — The whole or a portion of the ammonia absorbed by cer- 
tain anhydrous salts is retained with great force, and cannot be separated from 
them by heat. Anhydrous chloride of copper, for instance, absorbs a single 
equivalent of ammonia with the greatest avidity, and forms a green fusible 
matter, which the close analogy between copper and hydrogen would lead us 
to view as analogous in constitution to the compound formed by chloride of 
hydrogen and ammonia, or chloride of ammonium. It will, therefore, be re- 
presented as composed of chlorine united with ammonium, containing an atom 
of copper, in place of the fourth atom of hydrogen, or as NH 3 Cu,Cl, which 
may be called chloride of cuprammonium. The sulphate of copper, in like 
manner, retains half an equivalent of ammonia with great force, and forms a 
compound which may be represented as sulphate of copper combined with sul- 
phate of cuprammonium: 

CuO,S0 3 + (NH 3 CuO+SO s ,) 

which is analogous to the double sulphate of copper and ammonium: 
CuO,S0 3 4-(NH 4 ,0-f S0 3 .) 
Chloride of mercury forms a similar compound with half an equivalent of 
ammonia: 

HgCl+NH 3 Hg,Cl 

analogous to sal-alembroth, or the compound of chloride of mercury and sal- 
ammoniac: 

HgCl + NH 4 ,Cl. 

A different view of these and the other ammonium compounds is advocated 
bv Dr. Kane. Sal-ammoniac is considered by him as a species of double salt, 
as amide of hydrogen with chloride of hydrogen, H Ad-f H CI; and the salt 
I have named, chloride of cuprammonium, as a corresponding amide of hy- 
drogen with chloride of copper, H Ad 4- Cu CI. We agree in supposing these 
two salts to have the same constitution, but differ as to what that constitution 
is. To adapt the same explanation to the oxygen acid compounds, such as 
sulphate of ammonium, Dr. Kane assimilates them to the salts of the magne- 
sian class, which contain two equivalents of oxide. Adopting the hypothesis 
that two atoms of that class (in which water is included) are equivalent in 



HYDROGEN AND PHOSPHORUS. 297 

combination to one of the potash class, he views sulphate of copper, pos- 
sessing what I term its atom of constitutional water, as a. compound of sul- 
phuric acid with a base, which consists of an atom of oxide of copper and an 
atom of water, and represents it thus: 

Sulphate of copper . . CuO, H04S0 3 ; 
to which he assimilates the 

Sulphate of ammonium . AdH, HO-f SO s . 

The hypothesis of the equivalency of two atoms of the magnesian and one 
of the potash class, has received new support from Dr. Kane's researches; 
but it is still (in my opinion) too doubtful to form a safe basis for any theore- 
tical superstructure. At the same time, this hypothesis has enabled Dr. Kane 
to develope many new and interesting relations among the ammoniacal com- 
pounds, and may, perhaps, present a closer and more distinct view of the inti- 
mate constitution of these bodies, than the ammonium theory exhibits. At 
present, however, our theories of the constitution of compounds are too uncer- 
tain to be regarded otherwise than as artificial aids to facilitate our conception 
of the manner in which the formation of these bodies occurs, and of the trans- 
formations which they undergo; and a theory of constitution is, therefore, 
adopted more for its convenience than its truth. This state of things leads to 
the retention of the ammonium theory, which has introduced a degree of sim- 
plicity into our views of that particular class of ammoniacal compounds to 
which it is applicable, that could not easily be exceeded But its adoption 
must not be allowed to preclude the consideration of other theories, such as 
that of Dr. Kane, which facilitate investigations in the mean time, and may 
prove to be truer to nature in the end. 



SECTION IV. 

HYDROGEN AND PHOSPHORUS. 

Solid hydruret of phosphorus. — Magnus forms a phosphnret of potassium, 
by fusing phosphorus and potassium under naphtha. When this compound 
is thrown into water, a compound of phosphorus and hydrogen precipitates in 
the form of a yellow powder. It contains less hydrogen than the following 
compound. 

Phosphurefted hydrogen gas, PH 3 . — This gas, which is remarkable for its 
occasional spontaneous inflammability in air, was discovered by Gengembre 
in 1783, and has been successively investigated by several chemists; but its 
true nature was first ascertained by Rose, who proved it to be a compound 
analogous in constitution to ammoniacal gas, having phosphorus in the place 
of nitrogen. The pure gas is obtained by heating hydrated phosphorous acid, 
which is resolved into phosphuretted hydrogen and hydrated phosphoric acid: 
thus, 

4(3HO+P0 3 ) or 12HO and 4P0 3 = PH 3 and 9H043P0 5 . 

This gas does not inflame spontaneously when allowed to escape into air, 
but kindles when a light is applied to it, and burns with the white flame of 
phosphorus. A little air added to the gas, which had no effect at first, has 
been observed to produce occasionally an explosion after a time. The gas 
consists of 1 volume of phosphorous vapour and 6 volumes of hydrogen, con- 
densed into 4 volumes, so that it has the same combining measure as ammo- 



298 COMPOUNDS OF HYDROGEN. 

niacal gas. Its density is 1185. Phosphuretted hydrogen has a disagreeable 
alliaceous odour, is but slightly soluble in water, and has no alkaline reac- 
tion. 

The same gas, in a self-inflammable state, is obtained by boiling phospho- 
rus, lime and water together.* The first effect is the formation of hypophos- 
phite of lime, with the evolution of phosphuretted hydrogen gas: 

4P and 3CaO and 3HO = PH 3 and 3CaO-f 3PO; 

and phosphuretted hydrogen is again evolved, but mixed with a considerable 
quantity of free hydrogen, when the hydrated hypophosphite of lime is eva- 
porated to dryness, phosphate of lime being the residuary product. The self- 
lnflammabiiity of this gas must depend upon something extraneous. Rose 
has shown that the gas, after being passed through a long tube containing 
chloride of calcium, to dry it thoroughly, retains this property, for days, and 
undergoes no change in composition, whether kept in obscurity or exposed to 
sunshine,! and, therefore, rejects the theory of M. Leverrier,± that the pro- 
perty in question is due to another gaseous compound of phosphorus and hy- 
drogen, P-f 2H, present in a small quantity, and supposed to be decomposed 
by light, and to deposite a solid hydruret P-4-H, while the gas ceases to be 
self-inflammable. It was observed by myself,§ that the presence of phospho- 
rous vapour does not communicate spontaneous inflammability to the gas pre- 
pared from phosphorous acid; that the gas from hydrate of lime and phospho- 
rus is deprived of this property by porous absorbents, such as charcoal, by 
phosphoric acid, and by a most minute quantity of several combustible bodies, 
such as potassium, the vapours of ether and essential oils; and that the pro- 
perty was communicated to the gas of either process, by the addition of a 
snost minute quantity of the vapour of peroxide of nitrogen or of nitrous acid, 
varying from 1-1 000th to 1-1 0,000th of the volume of the gas. The hydro- 
gen gas which first comes off on making an addition of sulphuric acid to the 
gas bottle with zinc (page 195,) sometimes contains enough of peroxide of 
nitrogen, to impart spontaneous inflammability to phosphuretted hydrogen, to 
which it may be added. The self-inflammable gas from phosphorus and hy- 
drate of lime cannot contain peroxide of nitrogen, but it might be imagined to 
possess a trace of a corresponding compound of phosphorus and oxygen, if 
such a compound exists. 

Phosphuretted hydrogen decomposes some metallic solutions, such as those 
of copper and mercury, and forms metallic phosphurets. When the gas is 
pure, it is entirely absorbed by sulphate of copper and by chloride of lime. 
With hydriodic acid, phosphuretted hydrogen forms a crystalline compound, 
which is interesting from its analogy to sal-ammoniac. It may be formed by 

* [The production of PH 3 by means of lime is not unaccompanied with danger. The ex- 

periment is best performed by substituting the 
Fig. 87. solution of caustic potassa for the lime and 

water, and boiling in a retort as in the annexed 
figure. The retort A, should be completely 
filled with the solution before the beak is in- 
verted, and immersed under the water in the 
trough B, or the gas first formed, meeting with 
atmospheric air in the upper part and next of 
the retort will cause an explosion. The de- 
composition is the same as when lime is used, as 
will be evident on substituting K for Ca in the 
above formula. R. B.] 

t Liebig's Annalen der Pharmacie, v. 30, p. 320. (1839.) 

t An. de Ch. et de Ph. t. 60, p. 174. 

§ Phil. Mag. 3rd Series, vol. 5, p. 401. 




CARBON AND HYDROGEN. 299 

mixing together its constituent gases over mercury; or more easily by intro- 
ducing into a small tubulated retort, a mixture of 60 parts of iodine, 15 of 
phosphorus finely granulated, and mixing these bodies intimately with pounded 
glass; 8 or 9 parts of water are then added to the mixture, and the vapours 
which immediately come off are allowed to escape by a glass tube open at 
both ends, adapted to the beak of the retort, in which beautiful small crystals 
of the salt condense, of a diamond lustre. Rose has lately observed that these 
crystals, contrary to what is generally supposed, do not belong to the regular 
system, and are, therefore, not isomorphous with sal-ammoniac. They are 
decomposed by water, with evolution of phosphuretted hydrogen. 

Phosphuretted hydrogen, like ammonia, combines with the perchlorides of 
tin., titanium, chromium, iron, and antimony, forming white saline bodies. 
The combination with bichloride of tin is decomposed, with escape of the gas 
in the non-inflammable state, by water, and in the self-inflammable condition 
by solution of ammonia. 



CHAPTER III. 

COMPOUNDS OF CARBON. 



SECTION I. 



CARBON AND HYDROGEN. 



Light carburetted hydrogen, CH 2 . — This gas is a constant product of the 
putrefactive decomposition of wood and other compounds of carbon, under 
water, and is most readily obtained by stirring the mud at the bottom of stag- 
nant pools, and collecting the gas as it rises in an inverted bottle and funnel. 
It always contains 10 or 20 per cent, of carbonic acid, which may be sepa- 
rated from it by lime-water, and a small proportion of nitrogen. Carburetted 
hydrogen also issues, in some places, in considerable quantities from fissures 
in the earth, coming often from subterraneous deposites of coal; and in the 
working of coal mines, it is found pent up in cavities, and would appear some- 
times to be discharged from the fresh surface of the coal in sensible quantity. 
Hence, this gas is sometimes described as the inflammable air of marshes, 
and the fire-damp of mines. It is the most considerable constituent of coal 
gas, and of the gaseous mixture obtained on passing the vapour of alcohol 
through an ignited porcelain tube, but no artificial process is known to afford 
this gas in a state of purity. 

The density of light carburetted hydrogen is 559.5, and 1 volume of it con- 
tains 1 vol. of carbon vapour, and 2 vols, of hydrogen; but the combining mea- 
sure and equivalent of this compound are unknown. It is inodorous, neutral, 
respirable when mixed with air, not more soluble in water than pure hydro- 
gen, and has never been liquefied. Carburetted hydrogen requires twice its 
bulk of oxygen to burn it completely, and affords water and an equal bulk of 
carbonic acid. In air it burns, when lighted, with a strong yellow flame. It 
is a compound of considerable stability, but is decomposed in part when sent 
through a tube heated to whiteness, and resolved into carbon and hydrogen. 
This gas is not affected in the dark by chlorine, but when the mixture of these 



300 



COMPOUNDS OF CARBON. 



gases, in a moist state, is exposed to light, carbonic, and hydrochloric acid 
gases are produced. 

Although instantly kindled by flame, carburetted hydrogen requires a high 
temperature to ignite it. Hydrogen, sulphuretted hydrogen, and olefiant gas 
are all ignited by a glass rod heated to low redness, but. glass must be heated 
to bright redness or to whiteness, to inflame carburetted hydrogen. Sir H. 
Davy discovered that flame could not be communicated to an explosive mix- 
ture of carburetted hydrogen and air, through a narrow tube, because the cool- 
ing influence of the sides of the tube prevented the gaseous mixture contained 
in it from ever rising to the high temperature of ignition. A metallic tube 
has a greater cooling property, from its high conducting power, and conse- 
quently obstructs to a greater degree the passage of flame, than a similar tube 
of glass; and even the meshes of metallic wire-gauze, when they did not ex- 
ceed a certain magnitude, were found to be impermeable by flame. Experi- 
ments of this kind may be made upon coal-gas, the flame of which will be 
found incapable of passing through a sheet of iron-wire trellis, containing not 
less than 400 holes in the square inch. If the gas be allowed to pass through 
the trellis, and kindled above it, the flame, it will be found, does not return 
through the apertures to the jet whence the gas issues. Upon these observa- 
tions, Sir H. Davy founded his invaluable invention of the safety lamp, an in- 
strument indispensable to the safe working of the most extensive and valuable 
of our*coal fields. 

The safety lamp, as left by Davy, is simply an oil lamp, enclosed in a cage 
of wire-gauze, the upper part of which is double. (Fig. 88.) Mr. Buddie 
uses iron-wire gauze for the lamp, containing from 784 to 800 
Fig. 88. holes in the square inch. A crooked wire, which works tightly 
in a narrow tube passing upwards through the body of the lamp, 
affords the means of trimming the wick, without undoing the 
wire-gauze cover of the lamp. When the lamp is carried into 
an atmosphere charged with fire-damp, a blue flame is observed 
within the gauze cylinder, from the combustion of the gas, and 
the flame in the centre of the lamp may be extinguished. The 
miner should then withdraw, for although the gauze has often 
been observed to become red-hot, without inflaming the external 
explosive atmosphere, yet the texture of the gauze may be de- 
stroyed, if retained long at so high a temperature. It has always 
been known, since this lamp was first proposed, that when it is 
exposed to a strong current of the explosive mixture, the flame 
may pass too quickly through the apertures of the gauze to be 
cooled below the point of ignition, and, therefore, communicate 
with the external atmosphere. But this is easily prevented by 
protecting the lamp from the draught, and an accident from this 
cause is not likely to occur in a coal mine.* 

Carburetted hydrogen does not explode when mixed with air 
in a proportion much above or below the quantity necessary for 
its complete combustion. With 3 or 4 times its volume of air 
it does not explode at all, with 5£ or 6 volumes of air it de- 
tonates feebly, and with 7 to 8 most powerfully. With 14 
volumes of air, the mixture is still explosive, but with larger proportions 
of air, the gas only burns about the flame of the taper. The large quantity 
of air which is then mixed with the gas, absorbs so much heat as to prevent 

* For additional information respecting the safety lamp, the reader is referred to Davy's 
Essay on Flame, to Dr. Paris's Life and Dr. J. Davy's Life of Sir H, Davy, and to the 
Report of the Parliamentary Committee on accidents in mines, 1835. 



CARBON AND HYDROGEN. 



301 



the temperature of the gaseous atmosphere from rising to the point of igni- 
tion. 

Coal gas. — The products of the distillation of coal in an iron retort are of 
three kinds: a black oily liquid, of a heterogeneous nature, known as coal-tar, 
of which a considerable constituent, according to M. Dumas, is benzin; a 
watery fluid, known as the ammoniacal liquor, and the elastic fluids which 
form coal gas. To purify the gas, it is cooled by transmitting it through iron 
tubes or shallow boxes, in which it deposites some condensible matter; and it 
is afterwards exposed to milk of lime, to absorb sulphuretted hydrogen, which 
it invariably contains, and frequently afterwards to solution of sulphate of iron, 
which arrests a little hydrosulphuret of ammonia and a trace of hydrocyanic 
acid. The hydrate of lime is sometimes applied in the state of a damp pow- 
der, and not diffused through water. 

Dr. Henry obtained the following results from an examination of the gas from 
the best cannel coal, at different periods of the distillation : 

COAL GAS IN 100 VOLUMES. 





Density. 


Olefiant 
gas. 


Car buret ted 
Hydrogen. 


Carbonic 
oxide. 


Hydrogen. 


Nitrogen. 


At beginning of 
process . . . 
After five hours 
After ten hours 


650 
500 
345 


13 

7 



82.5 

56 

20 


3.2 

11 

10 




21.3 

60 


1.3 

4.7 
10 



Besides the constituents mentioned, coal gas when first made, contains small 
quantities of 



Ammonia, 

Sulphuretted hydrogen, 
Carbonic acid, 



Hydrocyanic acid, 
Sulphuret of carbon, 
Naphtha vapour.* 



All of these bodies are separated from it in the process of purification, except 
the last two, namely , naphtha vapour, which is the chief cause of the odour of coal 
gas, and sulphuret of carbon, which affords a little sulphurous acid when the 
gas is burned. The heterogeneous nature of the gaseous mixture is well shown 
upon introducing a quantity of dry iodine into a bottle of it, when several 
liquid and solid compounds of iodine are formed with the different hydrocarburets 
present. Iodine, on the other hand, is not affected in the slightest degree by 
fire-damp, but remains with its metallic lustre unchanged in that gas. Indeed, 
in the ordinary fire-damp no other combustible gas whatever can be found, be- 
sides light carburetted hydrogen. 

The superiority of coal gas, in illuminating power, depends principally upon 
the high proportion of olefiant gas and the denser hydrocarburets which it con- 
tains. The free hydrogen and carbonic oxide present give no light, and are 
positively injurious. As the highly illuminating constituents are dense, and 
contain much carbon, the value of coal gas is to a certain extent proportional to 
its density, and to the quantity of oxygen which it requires for complete com- 
bustion. In the analysis of coal gas, the different gases may thus be separated : 



* Dr. Henry's papers on coal gas are contained in the Phil. Trans, for 1808, 1820, and 
1824 ; his instructions for the analysis of mixed gases, in his Elements of Experimental 
Chemistry (1829,) vol. 2, p. 517. 
26 




302 COMPOUNDS OF CARBON, 

1st. Olefiant gas, naphtha vapour, and similar hydrocarburets, by mixing the 
gas, in a dark place, with half its bulk of chlorine, and afterwards washing with 
caustic potash ; 2ndly, carbonic oxide by potassium gently heated in the gas ; 
3rdly, the proportion of light curburetted hydrogen may be determined by deto- 
nating the mixture in a eudiometer (page 208,) with a measured quantity of 
oxygen, and ascertaining the quantity of carbonic acid formed, which retains 
the volume of the carburetted hydrogen ; 4thly, the free hydrogen, by observing 
the quantity of oxygen remaining, by means of a stick of phosphorus introduced 
into the gas, and thereby ascertaining the quantity of oxygen consumed in the 
combustion ; from this quantity deduct twice the measure of the carburetted 
hydrogen, and half the remaining measure of consumed oxygen represents 
the hydrogen ; 5thly, the residuary gas after these processes is the nitrogen of 
the coal gas. 

Structure of flame. — The quantity of light obtained from the combustion of 

coal gas depends entirely upon the manner in which it is burned, which will 

Fig 89 a PP ear fr° m tne consideration of the structure of luminous flames. 

The flame of a spirit lamp, candle, or gas-jet is hollow, as may be 

observed by depressing a sheet of wire trellis upon it, which gives a 
— c section of the flame ; the seat of the combustion being the margin 

of the flame, where alone the combustible vapour is in contact 
"" :B with the air. Of volatile carbonaceous combustibles, the flame, 

consists of three parts, which are represented in section, (Fig. 89.) : 

A, cone of vaporized combustible. 

B, sphere of partial combustion. 

C, sphere of complete combustion. 
In B, where the supply of air is insufficient for complete combustion, 

it is the hydrogen principally which burns, the carbon being liberated in solid 
particles, which are heated white hot from the combustion of that gas. The 
sphere B, indeed, is the luminous portion of the flame, for the light depends en- 
tirely upon the deposition of carbon, arising from the consecutive combustion of 
the two elements of the vapour. Gaseous bodies, however strongly heated, 
emit no light, or at most, not more than a sensible glow, and luminous flame 
has justly been described by Davy as always containing solid matter heated 
to whiteness. The same sphere of the flame, possessing an excess of combus- 
tible matter at a high temperature, takes oxygen from metallic oxides, such as 
arsenious acid, placed in it, and developes their metals. It is, therefore, often 
referred to as the deoxidizing or reducing flame. In the external hollow cone, 
C, the deposited carbon meets with oxygen, and is entirely consumed. The 
hottest point in the whole flame is within this sphere, near the summit of B. 
This part of the flame, possessing an excess of oxygen, at a high temperature, 
is the proper place for kindling a combustible, and is called the oxidizing flame ; 
its properties are the opposite of those of B. 

When coal gas is mingled with an equal bulk of air before being burned, 
it is found to lose half its illuminating power. It may be conveniently mixed 
with a quantity of air sufficient for its complete combustion, by placing over an 
argand burner, a brass chimney of 5 inches in height, provided with a cap of 
wire gauze ; when kindled above the wire gauze, the gas burns with a blue 
flame, not more luminous than that of sulphur. The flame is so feebly luminous 
because no deposition of carbon occurs in it. The quantity of heat is the same, 
whether the gas is burned so as to produce much or little light ; and where the 
gas is burned for heat, this mode of combustion has the advantage of giving a 
flame without smoke. The heat derived from coal gas burned in this manner 
is not, however, so intense as that of an argand spirit lamp. According to my 
own experience, the highest temperature is obtained from coal gas, when burned 
from that form of the argand recently introduced, in which the burner rises 



CARBON AND SULPHUR. 303 

through a truncated brass cone. A tangential current of air is thus occasioned, 
which sweeps the outer surface of the flame, and produces a perfect combustion. 
The burner should be provided besides with a metallic chimney of four inches 
in height, without the wire gauze* 

A result of the circumstances which determine the quantity of light from dif- 
ferent flames is, that the larger the flame till it begins to be smoky, the greater 
the proportion of light obtained from the consumption of the same quantity of. 
gas. It was observed that an argand burner, supplied with 1| cubic feet of gas 
per hour, gave as much light as a single candle ; with 2 cubic feet per hour the 
light was equal to 4 candles, and with 3 cubic feet to 1 candles. Hence ar- 
gands, bat-wings and other burners, in which a considerable quantity of gas is 
burned together, are more economical than plain jets. The brightness of or- 
dinary flame, which depends essentially upon the consecutive combustion of 
hydrogen and carbon, is increased by every thing which promotes the rapidity 
and intensity of the combustion, without deranging the order of oxidation, such 
as a rapid supply of air, and the substitution of pure oxygen for air, as in 
Mr. Gurney's JBude light. Not only is there then more light, because there is 
more combustion in the same time, but the temperature of the flame being 
greater, the luminous carbon is also heated to a higher degree of whiteness. 

Olefiant gas, C 4 H 4 or C 4 H 3 , H. — This gas was discovered in 1796, by cer- 
tain associated Dutch chemists, who gave it the name of olefiant gas, because 
it forms with chlorine a compound, having the appearance of an oil, from which 
the chlorides of carbon were afterwards derived (page 270.) This gas is pre- 
pared by heating together 1 measure of strong alcohol with 3 measures of oil 
of vitriol, in a capacious retort, till the liquid becomes black and efferves- 
cence begins, and maintaining it at that particular temperature. It is collected 
over water, which deprives it of a portion of ether vapour and sulphurous acid, 
with which it is accompanied. Olefiant gas burns with a white flame, and con- 
tains a large quantity of combustible matter in a given volume. It consists of 
S volumes of carbon vapour and 8 of hydrogen, condensed into 4 volumes, 
which gives for its density 981. It is now viewed as a compound of the organic 
radical acetyl with hydrogen, which is expressed in the rational formula stated 
above. Several other compounds of carbon and hydrogen exist but they will 
be studied with most advantage under organic chemistry, to which they properly 
belong. 



SECTION II. 

CARBON AND SULPHUR. 

Bisulphuret of carbon, CS 2 . — Charcoal ignited in an atmosphere of sulphur 
vapour, combines with that element, and forms a compound which holds the 
same place in the sulphur series that carbonic acid occupies in the oxygen 
series of compounds. The bisulphuret of carbon is a volatile liquid, and may 
be prepared by distilling, in a porcelain retort, yellow pyrites or bisulphuret of 
iron, with a fourth of its weight of well-dried charcoal, both in the state of 
fine powder and intimately mixed. The vapour from the retort is conducted 
to the bottom of a bottle filled with cold water, to condense it. Or sulphur 

* The form of argand recommended is known as the patent double-cone gas burner. 



304 COMPOUNDS OF CARBON. 

vapour may be sent over fragments of well dried charcoal in a porcelain or cast 
iron (not malleable iron) tube, placed across a furnace. The product is gene- 
rally of a yellow colour, and contains sulphur in solution, to free it from which 
it is redistilled in a glass retort, by a gentle heat. 

The bisulphuret of carbon is a colourless liquid, of high refracting power, 
and sp. gr. 1.272. Its vapour has a tension of 7.38 Paris inches (Marx) at 
50°, and the liquid boils at 110°; a cold of — 80 c can be produced by its 
evaporation in vacuo. This compound is extremely combustible, taking fire 
at a temperature which scarcely exceeds the boiling point of mercury. When 
a few drops of the liquid are thrown into a bottle of oxygen gas, or nitric ox- 
ide, a combustible mixture is formed, which burns, when a light is applied to 
it, with a brilliant flash of flame, but without a violent explosion. The bisul- 
phuret of carbon is insoluble in water, but it is soluble in alcohol. It dissolves 
sulphur, phosphorus and iodine. 

The bisulphuret of carbon is a sulphur acid, and combines with sulphur 
bases, such as the sulphuret of potassium, forming a class of salts which are 
called sulphocarbonates. Oxygen bases dissolves it slowly, and are converted 
into a mixture of carbonate and sulphocarbonate; thus 2 equivalents of potash 
with 1 of bisulphuret of carbon yield 2 equivalents of sulphuret of potassium 
and 1 of carbonic acid, which combine respectively with bisulphuret of carbon 
and potash. 

Solid sulphuret of carbon. — The charcoal left in the tube, after the process 
for the former compound, is much corroded, and contains a portion of sulphur 
which cannot be expelled from it by heat. Berzelius is disposed to consider 
this sulphur as in chemical combination with the carbon. 



SECTION III. 

CARBON AND NITROGEN. 

Bicarburet of nitrogen, or cyanogen, NC 2 . — This compound is a gas, 
which was first obtained by Gay-Lussac in 1815. It is prepared by heating 
the cyanide of mercury in a small glass retort, and is collected at the mercurial 
trough. The cyanide is resolved into running mercury and cyanogen gas, 
and frequently leaves a black coaly mass in the retort, which Professor John- 
ston has shown to consist of carbon and nitrogen, in the same proportions as 
the gas itself. 

Cyanogen gas contains 4 volumes of carbon vapour and 2 volumes of ni- 
trogen, condensed into 2 volumes; its density is 1819. When this gas is ex- 
ploded with twice its volume of oxygen, it affords 2 volumes of carbonic acid 
gas, and 1 volume of nitrogen, an experiment from which its composition may 
be deduced. Water at 60° absorbs 4.5 times its volume of this gas, and alco- 
hol 23 volumes. By a pressure of 3.6 atmospheres at 45°, cyanogen is con- 
densed into a limpid liquid, which evaporates again on removal of the pressure. 
Cyanogen burns with a beautiful purple flame in air or oxygen. The solution 
of cyanogen in water undergoes spontaneous decomposition. By alkalies the 
gas is absorbed, and a cyanide and cyanate formed. 

Cyanogen is a salt-radical, and unites with all the metals, as chlorine and 
iodine do, forming a class of cyanides. It also forms a hydrogen acid, namely, 
prussic or hydrocyanic acid. Cyanogen properly belongs to organic che- 
mistry, in which department its numerous combinations will be considered. 

Mellon, N 4 C 6 . — This is another salt-radical, and was formed by Liebig by 
heating the bisulphuret of cyanogen to redness, when it is resolved into sul- 



COMPOUNDS OF PHOSPHORUS. 305 

phur, bisulphuret of carbon, and mellon. It is a lemon yellow powder, inso- 
luble in water and alcohol. It unites directly with hydrogen and with potas- 
sium, forming hydromellonic acid and mellonide of potassium. 



CHAPTER IV. 



COMPOUNDS OF PHOSPHORUS.. 



Sulphuret of phosphorus. — Phosphorus and sulphur unite in all proportions,, 
with the evolution of much heat, and sometimes with explosion. These ele- 
ments are most safely united under hot water, of which the temperature, how- 
ever, must not exceed 160°, for otherwise sulphuretted hydrogen and phos- 
phoric acid may be produced with such rapidity as to occasion an explosion. 
The compounds of phosphorus and sulphur obtained in this manner appear 
not to be definite. They are more fusible and more inflammable than phos- 
phorus itself. Levol has shown that they often contain a little of the persul- 
phuret of hydrogen.* Serullas appears to have formed a definite sulphuret of 
phosphorus, by acting upon the liquid terchloride of phosphorus by sulphu- 
retted hydrogen. Hydrochloric acid was evolved and a solid amorphous body, 
of a lemon-yellow colour remained, which was a tersulphuret of phosphorus, 
corresponding with phosphorous acid. Berzelius ascertained that the sulphurets 
of phosphorus combine with sulphur bases, and produce colourless salts; but 
he did not carry the investigation beyond that point. 

Phosphuret of nitrogen, N 2 P. — Both the chlorides of phosphorus absorb 
ammoniacal gas, and form solid white compounds. The combination of the 
terchloride contains 2g equivalents of ammonia, but that of the perchloride, 
Rose did not find equally definite. When exposed to a strong red heat, with- 
out access of oxygen, these compounds leave a white amorphous body, which 
is the phosphuret of nitrogen.t It is most easily prepared by transmitting a 
stream of dry carbonic acid gas over the ammoniacal compound, in a tube of 
hard glass, heated by a charcoal fire, so long as vapours of sal-ammoniac sub- 
lime. 

The phosphuret of nitrogen is not soluble in any menstruum, nor acted 
upon by dilute acid or alkaline solutions. It is not affected when heated in an 
atmosphere of chlorine or sulphur, but is decomposed when heated in hy- 
drogen, with the formation of ammoniacal gas. The want of volatility and 
indifference to most chemical re-agents, which characterize this compound, are 
properties that could not have been anticipated in a compound of phosphorus 
and nitrogen. 

* An. de Ch. et de Ph. t. 67, p. 332, t Rose, lb. t. 54, p. 275. 



26* 



306 



METALLIC ELEMENTS. 



CHAPTER V. 
METALLIC ELEMENTS. 

GENERAL OBSERVATIONS. 

The metallic class of elements is considerably more numerous than the non- 
metallic class, embracing forty -two elementary bodies. Of these, seven only 
were known to the ancients, and of the remainder, a large proportion are of 
recent discovery. Their names and their densities, when accurately determined, 
with the dates and authors of their discovery, are contained in the following 
table, compiled from the work of Dr. Turner: — 

TABLE OF METALS. 



Name. 


Density. 


Dates and Authors of the Discovery. 


Gold . . . . 


19.257, Brisson. 


. 1 


Silver. . . . 


10.474, ditto . 


| 


Iron . . . . 


7.788, ditto . 


| 


Copper . . . 


8.895, Hatchett 


y Known to the Ancients. 


Mercury . . 


13.568, Brisson. 




Lead . . . . 


11.352, ditto . 




Tin ... . 


7.291, ditto . 




Antimony . . 


6.702, ditto . 


. 1490, Described by Basil Valentine. 


Bismuth. . . 


9.822, ditto . 


. 1530, Described by Agricola. 


Zinc . . , . 


6.861 to 7.1, ditto 


. 1 6th century, first mentioned by Paracelsus. 


Arsenic . . , 
Cobalt . . . 


5.884, Turner . 
8.538, Hauy . 


1 1733, Brandt. 


Platinum . . 


20.98, Brisson 


. 1741, Wood, assay-master, Jamaica, 


Nickel . . . 


8.279, Richter 


. 1751, Cronstedt. 


Manganese . . 


6.850, Bergman 


. 1774, Gahn and Scheele. 


Tungsten . . 


17.6, D'Elhuyart 


.1781, D'Elhuyart. 


Tellurium . . 


6.115, Klaproth 


.1782, Mailer. 


Molybdenum . 


8.615, Bucholz 


.1782, Hielm. 


Uranium . . 


9.000, ditto . 


. 1789, Klaproth. 


Titanium . . 


5.3, Wollaston 


. 1791, Gregor. 


Chromium . . 


. • • 


. 1797, Vauquelin. 


Columbium 


. . • 


. 1802, Hatchett. 


Palladium . . 
Rhodium . . 


11.3 to 11.8, Wollastc 


n I 1803, Wollaston. 


Iridium . , . 


... 


. 1803, Descotils and Smithson Tennant, 


Osmium . . . 


. • . 


. 1803, Smithson Tennant. 


Cerium . . . 




. 1804, Hisinger and Berzelius,. 


Potassium . . 


0.865 ^ Gay-Lussac 
0.972} and Thenard 


> 


Sodium . . . 


| 


Barium . . . 


.... 


Y 1807, Davy. 


Strontium . . 


• . • 


1 


Calcium . . . 


• • 


J 


Cadmium . . 


8.604 Stromeyer . 


. 1818, Strcmeyer. 


Lithium . . . 




. 1818, Arfwedeon, 


Zirconium . . 






. 1824, Berzelius. 


Aluminum . . 






1 


Glucinum . . 


. » 




V 1828, Wohler. 


Yttrium . . . 


. 




J 


Thorium 


, . 




. 1829, Berzelius. 


Magnesium 


. 




. 1829, Bussy. 


Vanadium . . 


, , 




. 1830, SeftstrOm. 


Lantanum . . 






. 1839, Mosander. 



GENERAL OBSERVATIONS. 307 

Of the physical properties of metals and their combinations with each other, 
the most characteristic is their lustre and power to reflect much of the light 
which falls upon them, a property exhibited in a high degree by burnished steel, 
speculum metal, and the reflecting surface of mercury in glass mirrors. Metals 
are also remarkable for their opacity, although they have a certain degree of 
transparency in a highly attenuated state, as fine gold-leaf allows light of a green 
colour to pass through it. They are peculiarly the conductors of electricity, 
and also the best conductors of heat. The most dense substances in nature are 
found among the metals, gold, for instance, being upwards of nineteen, and 
platinum nearly twenty-one times heavier than an equal bulk of water. But 
some of the metals, notwithstanding, are very light, potassium and sodium float- 
ing upon the surface of water. 

Certain metals possess a valuable property, malleability, depending upon a 
high tenacity with a certain degree of softness ; particularly gold, silver, copper, 
tin, platinum, palladium, cadmium, lead, zinc, iron, nickel, potassium, sodium, 
and solid mercury. These metals may all be hammered out into plates, or even 
into thin leaves. In zinc this property is found in the highest degree between 
300° and 400°, and in iron at a degree of temperature exceeding a red heat. 
The same metals are likewise ductile, or may be drawn into wires, although the 
ductility of different metals is not always proportional to their malleability, iron 
being highly ductile, although it cannot be beaten into very thin leaves. By a 
peculiar method, Dr. Wollaston formed gold wire so small that it was only 
l-5000th of an inch in diameter, and 550 feet of it were required to weigh one 
grain. He also obtained a wire of platinum not more than 1 -30,000th of an inch 
in diameter.* The tenacity of different metals is determined by ascertaining 
the weight required to break wires of them having the same diameter. Iron 
appears to possess that property in the greatest, and lead in the least degree. 
It has been observed by M. Baudrimont that the tenacity of wires of iron, copper, 
and brass is much injured by annealing them.f A few of the malleable metals 
can be welded, or portions of them joined into one by hammering them together. 
Pieces of iron or platinum may be united in this manner at a bright red heat, 
and fragments of potassium may be made to adhere by pressing them together 
with the hand at the temperature of the air. Many metals are only malleable 
in a low degree, and some are actually brittle, such as bismuth, antimony, and 
arsenic. 

The metals, with the exception of mercury, are all solid at the temperature 
of the air, but they may be liquefied by heat. Their points of fusion are very 
different, as will appear from the following table:J 



TABLE OF THE FUSIBILITY OF DIFFERENT METALS, 

Fahr. 

/'Mercury . . — 39° Different chemists. 

Potassium . . J36 U ay-Lussac and Thenard 

Sodium . . 190 £ J 

Cadmium . . . 442 Stromeyer. 

Tin . . . 442 1 

Bismuth . . 497 VCrichton. 

Lead . . . 612 ) 



Fusible below a 
red heat. 



Tellurium — rather less 

fusible than lead. Klaproth. 

Arsenic — undetermined. 
Zinc . . , 773 Daniell. 

Antimony — a little be- 
„ low a red heat. 



Phil. Trans. 1813. t An. de Ch. et de Ph. t. 60, p. 78. 

Dr. Turner's Elements of Chemistry, p. 414. 



308 



METALLIC ELEMENTS. 



Infusible below a 
red heat. 



Silver . . . 1873 ^ 

Copper . . 1996 V Daniell. 

Gold ."..', . 2016 S 

Cobalt — rather less fusi- 
ble than iron. 

Iron, cast . t 2786 Daniell. 

Manganese 1 6 . .' ( Re( l uirin g the hi g nest heat o fa smith's forge. 

Nickel — nearly the same as cobalt. 

Palladium. 

Almost infusible, and not \ 

to be procured in buttons 

by the heat of a smith's 

forge. 



Molybdenum 

Uranium 

Tungsten 

Chromium 
Titanium 
Cerium 
Osmium 
Iridium 
Rhodium 
Platinum 
k Columbium , 



Fusible before the oxi-hy- 
drogen blow-pipe. 



1 Infusible in the heat of a smithes forge, but fusible before 



the oxi-hydrogen blow-pipe. 



The metallic elements are, in general, highly fixed substances, although it 
is probable that all of them may be dissipated at the highest temperatures. 
The following metals are so volatile as to be occasionally distilled, — cadmium, 
mercury, arsenic, tellurium, sodium, potassium and zinc. 

All the metals are capable of uniting with oxygen, but they differ greatly 
from each other in their affinity for that element. The greater number of them 
absorb oxygen from dry air at the usual temperature, and undergo oxidation, 
which is only slight and superficial in many, when they are in mass, but may 
be complete and perfect in the same metals, when they are highly divided, 
and in a favourable state for combination, as in the Lead and iron pyrophorus 
exposed to air. The same metals exhibit, at a high temperature, a more in- 
tense affinity for oxygen, and combine with combustion. The only metals 
which do not unite with oxygen directly in any circumstances are silver, pal- 
ladium, platinum, gold, and probably rhodium and iridium. 

The metals have been arranged in six groups or sections, differing in their 
degrees of oxidability. 1. Metals which decompose water even at 32°,. with 
lively effervescence, namely, potassium, sodium, lithium, barium, strontium, 
calcium, and probably magnesium. 2. Metals which do not decompose water 
at 32°, like the metals of the preceding class; they do not decompose it with a 
lively effervescence, except at a temperature approaching 212° or even higher, 
but always much below a red heat. In this class are found glucinum, alumi- 
num, zirconium, thorium, yttrium, cerium, and manganese. 3. Metals which 
do not decompose water except at a red heat, or at the ordinary temperature 
with the presence of strong acids. This section comprehends iron, nickel, 
cobalt, zinc, cadmium, tin, chromium, and probably vanadium. Iron is rapidly 
corroded in water, containing carbonic acid, with the evolution of hydrogen. 
4. Metals which decompose the vapour of water at a red heat with considera- 
ble energy, but which do not decompose water in presence of the strong acids. 
They are tungsten, molybdenum, osmium, columbium, titanium, antimony, 
and uranium. These metals appear to be incapable of decomposing water in 
contact with acids, because their oxides have but a small basic power, being 
indeed bodies which are ranked among the acids. 5. Metals of which the 
•oxides are not decomposed by heat alone, and which decompose water only 
in a feeble manner, and at a very high temperature. They are also distin- 
guished from the preceding class by their tendency to form basic and not acid 



GENERAL OBSERVATIONS. 309 

oxides. These metals are copper, lead, and bismuth. 6. Metals of which 
the oxides are reducible by heat alone at a temperature more or less elevated; 
these metals do not decompose water in any circumstances. They are mer- 
cury, silver, palladium, platinum, gold, and probably rhodium and iridium.* 
It is to be remarked of nearly all the metals which decompose the vapour of 
water, and consequently separate hydrogen from oxygen at a certain tempe- 
rature, that their oxides are reduced, notwithstanding, with great facility by 
hydrogen gas, and within the same limits of temperature. This anomalous 
result has already been adverted to in regard to iron (p. 151.) 

Of the thirteen non-metallic elements, hydrogen only forms a basic oxide 
capable of uniting with acids. It is a general character of the metals, on the 
contrary, to form such oxides, if tellurium be excepted, which is more analo- 
gous in its chemical properties to sulphur than to the metals. Hence, as the 
former class are principally salt-radicals, the latter are principally basyles. 

The protoxides of metals are uniformly and strongly basic, but this feature 
becomes less distinct in their superior oxides, and passes into the acid charac- 
ter in the high degrees of oxidation of which some metals are susceptible. 
Thus, of manganese, the protoxide is a strong base, the deutoxide basic but 
in a less degree than the protoxide; the peroxide indifferent, and the still higher 
oxides are the manganic and hypermanganic acids, which are respectively 
isomorphous with sulphuric and hyperchloric acids. A few metals which 
have no protoxides, such as arsenic and antimony, are most remarkable for 
the acids they form with oxygen, and thus more resemble in their chemical 
history the elements of the non-metallic class. It is indeed impossible to 
draw an exact line of demarcation between the two classes of elements, either 
with reference to their physical or chemical properties. 

Besides combining with oxygen, metals combine with sulphur, chlorine, 
and with other salt-radicals, whether simple or compound, and hence sulphu- 
rets, chlorides, and numerous other series of metallic compounds. Of these 
series the sulphurets most resemble the oxides of the same metals; the chlorides 
and other series partake more strongly of the saline character. Each metal, 
or class of metals affects combination with oxygen in certain proportions, and 
combines also with sulphur, chlorine, &c, in the same proportions. Hence, 
given the formulae of the oxides of a metal, the formula of its sulphurets. 
chlorides, <fec, may generally be predicated, as they correspond with the for- 
mer. Thus the oxides of iron being FeO and Fe 2 6 3 , the sulphurets are FeS 
and Fe 2 S 3 , and the chlorides FeCl and Fe 2 Cl,; the oxides of arsenic, or ar- 
senious and arsenic acids, being As0 3 and AsO., the sulphurets of that metal 
are AsS J and AsS 5 , and the chlorides AsCl 3 and AsCl 5 . But sometimes a 
metal unites with sulphur in more ratios than with oxygen, both iron and 
arsenic, for example, possessing each a sulphuret to which they have no cor- 
responding oxide, namely, martial pyrites and realgar, of which the formulae 
are FeS 2 t and AsS 3 . The potassium family of metals combine also with 
three and five equivalents of sulphur, without all uniting with oxygen in such 
high proportions. Again, certain metals of the magnesian and its allied fami- 
lies, such as manganese and chromium, form acid compounds with oxygen, to 
which no corresponding sulphurets exist, such as manganic and chromic acids. 
Mn0 3 and Cr0 3 . But the circumstance that these acids are isomorphous 
with sulphuric acid, and the metals they contain isomorphous with sulphur, 
appears to be a sufficient reason why there should not be similar sulphur acids. 
The chlorides of a metal generally correspond in number, as they always do 
in composition, with the oxides; in some cases they are less numerous, but 
never, I believe, more numerous than the oxides of the same metal. 

* Regnault, Ann. de Ch. et de Ph. t. 62, p. 368. 
t Vide, p. 122, note. 



310 METALLIC ELEMENTS. 

Combination takes place within a series, that is, oxides combine with 
oxides, sulphurets with sulphurets. Those members of the same series which 
differ greatly in chemical characters being most disposed to combine together, 
as oxygen acids with oxygen bases, sulphur acids with sulphur bases. Chlo- 
rides also combine with chlorides, to form double chlorides, and iodides with 
iodides. 

Compounds belonging to different series, on the contrary, do not combine 
together, but often mutually decompose each other, when brought into con- 
tact. Thus hydrochloric acid and potash do not unite, but form water and 
chloride of potassium, by mutual decomposition, as explained in the following 
diagram: — 

Before decomposition. After decomposition. 

Hydrochloric C Hydrogen 
acid. I Chlorine 

Potash $ 0x yg en 

^Potassium Chloride of Potassium. 

In the same manner, peroxide of iron, dissolved in hydrochloric acid, produces 
water and a perchloride of iron corresponding with the peroxide: 3HC1 and 
Fe 2 3 = 3HO and Fe 2 Cl 3 . And in all cases when a metallic oxide dis- 
solves in hydrochloric acid, without evolution of chlorine, the chloride pro- 
duced necessarily corresponds with the oxide dissolved. Again, orpiment, or 
sulpharsenious acid does not combine with potash, when dissolved in that alka- 
line oxide, but gives rise to the formation of certain proportions of arsenious 
acid, and sulphuret of potassium: — 

Before decomposition. After decomposition. 

Sulpharsenious C Arsenic * ~" ^^Arsenious acid. 

acid. 1 3 Sulphur 





3 Potash S ^ Oxygen 

£3 Potassium -r* 3 Sulphuret of potasium. 

Two pairs of compounds of different series then co-exist in the liquid, an 
oxygen acid, arsenious acid, which unites with the oxygen base, potash, and a 
sulphur base, sulphuret of potassium, which unites with undecomposed sul- 
pharsenious acid. Hence the result of dissolving orpiment in potash is the 
decomposition of both compounds and formation of two salts of different se- 
ries, arsenite of potash and sulpharsenite of sulphuret of potassium. 

The union of metallic compounds of the oxygen and sulphur series is a rare 
occurrence. But the red ore of antimony is such a combination, and oxisul- 
phurets of mercury also exist. Compounds of metallic oxides with metallic 
chlorides, and with other highly saline binary compounds, are more frequent; 
but they are not to be placed in the same category with the compounds of in- 
dividuals both belonging to the same series, which last are neutral salts. For 
a metallic oxichloride may generally, if not always, be viewed as a chloride to 
which a certain proportion of metallic oxide is attached, like constitutional 
water in a hydrated salt. That metallic oxide is likewise always of the mag- 
nesian class, or of a class allied to it. Oxichlorides are then to be associated 
with those salts of oxygen-acids usually denominated subsalts (page 138;) the 
oxichlorides of lead and of copper; PbCl-f3PbO and CuCl-f-3CuO, with 
the subacetates and subsulphates of the same metals. 

Arrangement of metallic elements. — A distribution of the metals into three 
classes is generally made, composed respectively of the metals of the alkalies 
and alkaline earths, the metals of the earths, and the metals proper. The 
latter class again is subdivided, according to the affinity of the metals contained 



GENERAL OBSERVATIONS. 



311 



in it for oxygen, into the two groups, the noble and common metals, the oxides 
of the former, such as gold, silver, &c, abandoning their oxygen at a high 
temperature, while the oxides of the latter, lead, copper, &c, are undecom- 
posable by heat alone. In treating of the metals, I shall introduce them in the 
order which appears to facilitate most the study of their combinations, with a 
general reference to that old classification. For subdivisions, I shall avail my- 
self of the natural families into which the elements have been arranged (119,) 
which have the advantage of bringing together those metals of which the com- 
pounds are most frequently isomorphous. The different metals will therefore 
be grouped under the following heads: — 



I. Metallic bases of the alkalies — three metals: 



Potassium 
Sodium 
Lithium . 



Oxides. 

Potash. 

Soda. 

Lithia. 



IL Metallic bases of the alkaline earths — four metals: 



Barium . 

Strontium .... 

Calcium .... 

Magnesium .... 

III. Metallic bases of the earths proper — five metals: 



Oxides. 
Barytes. 
Strontian. 
Lime. 



Magnesia. 



Aluminum 

Glucinum 

Zirconium 

Yttrium 

Thorium 



Oxides. 

Alumina. 

Glucina. 

Zirconia. 

Yttria. 

Thorina. 



IV. Metals proper, of which the protoxides are isomorphous with magnesia, 
with bismuth — nine metals: 



Manganese. 

Iron. 

Cobalt 

Nickel. 

Zinc. 

V. Other metals proper having isomorphous relations with the magnesian 
family — seven metals: 

Tin. 

Titanium. 
Chromium, 
Vanadium. 



Cadmium. 
Copper. 
Lead. 
Bismuth. 



Tungsten. 

Molybdenum. 

Tellurium. 



VI. Metals isomorphous with phosphorus- 
Arsenic. I 



-two metals: 

Antimony, 
s proper, not included in the foregoing classes, of which the 



oxides are not reduced by heat alone—four metals: 

Uranium. 
Cerium. 



Lantanum. 

Columbium or Tantalum. 



312 POTASSIUM. 

VIII. Metals proper, of which the oxides are reduced to the metallic state 
by heat, (noble metals) — three metals: 

Mercury. Gold. 

Silver. 

IX. Metals peculiar to native platinum (noble metals) — five metals: 



Platinum. 

Palladium. 

Iridium. 



Osmium. 
Rhodium. 



ORDER I. 

METALLIC BASES OF THE ALKALIES, 

SECTION I. 

POTASSIUM. 

Syn. Kalium. Eq. 490 or 39.3; K. 

The alkalies and earths have long been named and distinguished from each 
other, but they were not known to be the oxides of peculiar metals till a recent 
period. The terms applied to the new metallic bases are formed from the 
names of their oxides, as potassium from potash, and calcium from calx, a 
name sometimes given to lime; while the original names of the oxides are still 
retained, as those of ordinary objects, and not superseded by appellations indi- 
cating their relation to the metals, such as oxide of potassium for potash, or 
oxide of calcium for lime. 

Preparation. — In 1807, Sir H. Davy made the memorable discovery that 
potash is resolved by a powerful voltaic battery into potassium and oxygen. 
He placed a moistened fragment of hydrate of potash upon mercury, intro- 
ducing the terminal wire from the zinc extremity of an active battery (the 
chloroid) into the fluid metal, and touching the potash with the other terminal 
wire (the zincoid;) bubbles of oxygen gas appeared at the latter wire, and po- 
tassium was liberated at the former, and dissolving in the mercury, was pro- 
tected from oxidation by the air. To effect this decomposition, Davy em- 
ployed a battery of 200 pairs of four-inch plates; but an amalgam of potassium 
may be as readily obtained by a more simple voltaic apparatus, in the manner 
described at page 183. These processes, however, afford potassium only in 
minute quantity. Soon after the existence of this metal was known, Gay-Lus- 
sac and Thenard discovered that potash is decomposed by iron at a white heat, 
and they contrived a process by which a more abundant supply of the metal 
was obtained. It was afterwards noticed by Curaudau that potash, like the 
oxides of common metals, is decomposed by charcoal as well as by iron, which 
is the basis of the process for potassium now always followed. 

This interesting and useful process is described by Mitscherlich, as it is 
successfully pursued in Germany. Whenever charcoal is used to deprive a 
metallic oxide of its oxygen, the former must be in a^tate of minute division, 
and be intimately mixed with the latter. Carbonate of potash requires thi3 



PREPARATION OF POTASSIUM. 



313 



precaution the more, that it fuses at a red heat, and is thus apt to separate from 
the charcoal, and sink below it. It is found that the best means to obtain a 
proper mixture of these substances is to calcine a salt of potash containing a ve- 
getable acid, which leaves a large quantity of charcoal, when decomposed. 
Crude tartar (bitartrate of potash) is preferred, and for one operation six pounds 
of that salt are ignited in a large crucible or melting-pot provided with a lid, 
so long as combustible gases are disengaged. The crucible is then withdrawn 
from the fire, and is found to contain a black mass, which is the mixture of 
charcoal and carbonate of potash, known as black flux. It is reduced to 
powder, while still warm, and immediately mixed with about ten ounces of 
wood-charcoal in small pieces, or in a coarse powder, from which the dust has 
been separated by a sieve. The use of this additional charcoal is to act as a 
sponge, and absorb the potash when liquefied by heat. The mixture is intro- 
duced into a bottle of wrought iron, and a mercury bottle (page 187) answers 
well for the purpose, but must be heated to redness before hand, to expel a 
little mercury that remains in it. The mouth of the bottle is enlarged a little 
by means of a round file, and a straight iron tube of 4 or 5 inches in length 
fitted into the opening, by grinding. The bottle and tube thus form a retort, 

Fig. 90. 




which is supported horizontally in a brick furnace, as represented (Fig. 90,) 
in which a is the iron bottle resting upon two bars of iron, o o, to which it 
may also be firmly bound by iron wire. These bars cross the furnace at a 
height of 5 or 6 inches above the grate-bars. A mixture of equal parts of 
coal and coke makes an excellent fuel for this furnace. The tube b of the 
bottle projects through an aperture in the side-wall of the furnace, and enters 
a receiver of a peculiar construction required to condense the potassium, which 
distils over. This receiver is composed of two separate copper cylinders or 
oval boxes, hard soldered, similar in form and size, which are represented in 
section in figure 91, the one b n d being introduced within the other g h k t 
and thus forming together a vessel of which b n d is the cover. It will also 
be observed that b n d is divided into two cells by a diaphragm i. of the same 
27 




314 POTASSIUM. 

length as the cylinder, and descending with it to within two inches of the bot* 
torn h of g h k. A riband of copper g is soldered around b n d, so as to form 
p q- a ledge, which is seen in both figures, and serves as a sup- 

port for a cage of iron-wire c d, placed over the receiver 
» during the distillation; to hold ice, and also to shed the water 

from the liquefaction of that ice, which falls into a tray p be- 
low, and flows off by the tube /. The cover has also two 
short copper tubes d and b, of which the copper of b is 
notched so as to clasp firmly by its elasticity the tube b from 
the iron bottle, which is fitted into it. The other tube d, 
which is exactly opposite to 6, is fitted with a cork, and the 
diaphragm i has a small hole in it to allow of a rod being 
passed through b and cl. In the same part of the apparatus is a third opening, to 
which a glass tube x is fitted by a cork, for the escape of uncondensible gases. 
The receiver is filled to about one-third with rectified petroleum, a liquid con- 
taining no oxygen, so as to come near to, but not to cover the bottom of the 
partition ?'. The length of the bottle is 11 inches, its width 4, and the other 
parts of the apparatus are designed upon the same scale. 

Potassium and carbonic oxide gas are the principal products of the decom- 
position of the carbonate of potash, but other substances besides these are 
found in the receiver, namely, a black mass very rich in potassium, some oxa- 
late and croconate of potash and free potash, with a portion of charcoal powder 
carried over mechanically. Part of these products appear to be formed, after the 
reduction of the potassium, by the mutual reaction of that metal, carbonic oxide 
and petroleum. The process is found to succeed best when the iron tube b is 
so short that it can be maintained at a red heat through its whole length during 
the operation, while the receiver is kept at a very low temperature; the potas- 
sium then falls from the tube, drop by drop, into the receiver, and does not re- 
main long in contact with carbonic oxide, which is known to combine readily 
with that metal. One or two other points should also be attended to. The con- 
nexion between the tube b and the receiver is not made till the iron bottle has 
been heated to redness, to allow of the escape of a little water, and of a trace 
of mercury, which had remained in the bottle in the state of vapour, and which 
come off first. The joining of the tube b is not air-tight at first, and allows a 
little potassium vapour to escape, but this burns and forms potash, which im- 
mediately closes the openings. This tube being always incandescent, and the 
refrigeration properly made, the reduction sometimes proceeds without inter- 
ruption. But the tube is sometimes obstructed, as appears by the gases ceasing 
to escape by x. Haste must then be made to open the tube b, and to clear it 
by means of a flattened iron rod /, slightly hooked at its anterior extremity. 
Care has been taken to mark on this rod, with the scratch of a file, how far it 
has to penetrate into the apparatus to reach the mouth of the bottle, and it 
must not be introduced farther. The current of air through the furnace is re- 
gulated by a register valve in the chimney, and the fire stirred frequently so as 
to prevent the formation of cavities; the operator being guided in the manage- 
ment of the fire by the rapidity of the current of gas which escapes by the 
tube x. To terminate the operation, the grate bars may be thrown down, by 
which the fuel will fall into the ash-pit. The quantity of crude tartar men- 
tioned yields about 4 ounces of potassium, which is about 4 per cent, of its 
weight. The potassium thus obtained, containing a little carbon chemically 
combined with it, is submitted, together with the black mass found in the re- 
ceiver, to a second distillation. For this purpose a smaller iron bottle with a 
bent tube maybe employed, the end of which is covered by rectified petroleum 
in a capacious flask, used as a receiver.* 

* Mitscherlich, Elemens de Chimie, t, 3, p. 8. 



COMPOUNDS OF POTASSIUM. 315 

Properties. — Potassium is solid at the usual temperature, but so soft as to 
yield like wax to the pressure of the fingers. A fresh surface has a white co- 
lour, with a shade of blue, like steel, but is almost instantly covered by a dull 
film of oxide, when exposed to air. The mettle is brittle at 32°, and has been 
observed crystallized in cubes: it is semi-fluid at 70°, and becomes completely 
liquid at 150°. It may be distilled at a low red heat, and forms a vapour of a 
green colour. Potassium is considerably lighter than water, its density being 
0.865 at 60°. 

Potassium oxidates gradually without combustion when exposed to air, but 
heated till it begins to vapourize, it takes fire and burns with a violet flame, 
The avidity of this metal for oxygen is strikingly exhibited when a fragment 
of it is thrown upon water. It instantly decomposes the water, and so much 
heat is evolved as to kindle the potassium, which moves about upon the surface 
of the water, burning with a strong flame, of which the vivacity is increased 
by the combustion of the hydrogen gas disengaged at the same time. A glo- 
bule of fused potash remains, which continues to swim about upon the surface 
of the water for a few seconds, but finally produces an explosive burst of steam, 
when its temperature falls to a certain point, illustrating the phenomenon of a 
drop of water on a hot metallic plate (page 55.) 

Potassium appears to have the greatest affinity of all bodies for oxygen, at 
temperatures which are not exceedingly elevated. It decomposes nitrous and 
nitric oxides, and also carbonic oxide gas at a red heat, although potash is re- 
duced to the metallic state by charcoal at a white heat. It has already been 
stated that the oxides and fluorides of boron and silicon are decomposed bv 
potassium, and besides these elements, several of the metallic bases of the 
earths are obtained by means of this metal. It is indeed a reducing agent of 
the greatest value. 

COMPOUNDS OF POTASSIUM. 

Potash or potassa; KO; 590 or 47.26. — Potassium exposed in thin slices to 
dry air becomes a white matter, which is the protoxide of potassium or potash. 
This compound is fusible, at a red heat, and rises in vapour at a strong white 
heat. It unites with water, with ignition, and forms a fusible hydrate, which 
is the ordinary condition of caustic potash. 

The hydrate of potash (KO, HO) is obtained in quantity from the carbonate 
of potash. Equal weights of that salt and of quick-lime are taken, the latter of 
which is slaked with water, and falls into a powder consisting of hydrate of lime ; 
the former is dissolved in from 6 to 10 times its weight of water, and both boiled 
together for half an hour in a clean iron pan. The lime abstracts carbonic acid 
from the potash, and becomes carbonate of lime; a reaction which maybe illus- 
trated by adding lime water to a solution of carbonate of potash when a pre- 
cipitate of carbonate of lime falls. When the potash has been deprived entirely 
of carbonic acid, a little of the clear liquid taken from the pan will be found not 
to effervesce upon the addition of an acid to it. It is remarkable that the de- 
composition is never complete, if the carbonate of potash be dissolved in less 
than the prescribed quantity of water. Liebig has observed that a concen- 
trated solution of potash decomposes carbonate of lime, and consequently hy- 
drate of lime could not, in the same circumstances, decompose carbonate of 
potash. The pan being covered by a lid, may be allowed to cool ; as the inso- 
luble carbonate of lime and the excess of hydrate of lime subside, a consider- 
able quantity of the clear solution of potash may be drawn off by a syphon, and 
the remainder may be obtained clear by filtration. In the latter operation a large 
glass funnel may be employed, to support a filter of washed cotton calico, into 
which what remains in the pan is transferred. A small portion of liquid, which 
passes through turbid at fW should be returned to the filter. As the solution 



316 POTASSIUM. 

of potash absorbs carbonic acid, it is proper to conduct its filtration with as little 
exposure to air as possible ; on which account the mouth of the funnel should 
be covered by a plate, and the liquid which flows from it be immediately received 
in a bottle, in the mouth of which the funnel may be supported. The bottle in 
which potash is preserved should not be of crystal, or of a material containing 
lead, as the alkali corrodes such glass, particularly when its natural surface has 
been cut 

To obtain the solid hydrate of potash, the preceding solution is rapidly evapo- 
rated in a clean iron pan or silver basin, till an oily liquid remains at a high 
temperature, which contains no more than a single equivalent of water. This 
liquid is poured into cylindrical iron moulds, to obtain it in the form of 
sticks, which are used by surgeons as a cautery, and are the potassa or po- 
tassa fusa of the pharmacopeia; a form in which it is also convenient to 
have potash for some chemical purposes. The sticks generally contain a por- 
tion of carbonate of potash, besides a little oxide of iron and peroxide of potas- 
sium, the last of which gives occasion to the evolution of a little oxygen gas 
when the sticks are dissolved in water. To obtain hydrate of potash free from 
carbonate, the sticks are dissolved in alcohol, in which the foreign impurities are 
insoluble, and the alcoholic solution is evaporated to dryness. 

The pure and fused hydrate of potash is a solid white mass of a structure 
somewhat crystalline, of sp. gr. 1.706, fusible at a heat under redness. It is a 
protohydrate, and cannot be deprived of its combined water by the most intense 
heat. It destroys animal textures. It rapidly deliquesces in damp air from the 
absorption of moisture, is soluble in half its weight of water, and also in alcohol. 
Mixed in powder with a small quantity of water, it forms a second crystalline 
combination which is a terhydrate ; and its solution in water affords, at a very 
low temperature, crystals in the forms of four-sided tables and octohedrons, 
which are a pentahydrate, KO, HO+4HO. 

The solution of potash, or potash ley, has a slight but peculiar odour, charac- 
teristic of caustic alkalies, which they acquire from their action upon organic 
matter, derived from the atmosphere or other sources. The skin and other 
animal substances are dissolved by this liquid. It is highly caustic, and its taste 
intensely acrid. It has those properties which are termed alkaline in an emi- 
nent degree. It neutralizes the most powerful acids, restores the blue colour 
of reddened litmus, changes the blue infusion of cabbage into green, but in a 
short time altogether destroys these vegetable colours. It acts upon fixed oils, 
and converts them into soaps, which are soluble in water. It absorbs carbonic 
acid with great avidity from the air, on which account it should be preserved in 
well stopped bottles. 

The presence of free potash or soda, in solutions of their carbonates, may be 
discovered by nitrate of silver, the oxide of which is precipitated of a brown 
colour by the caustic alkali, while the white carbonate of silver only is precipi- 
tated by the pure carbonated alkali. Potash, whether free or in combination 
with an acid as a soluble salt, may be detected and distinguished from soda and 
all other substances, by means of certain acids, &c, which form sparingly solu- 
ble compounds with that alkali. A strong solution of tartaric acid produces a 
precipitate of bitartrate of potash,'in a liquid containing 1 per cent, of any potash 
salt. The precipitate is crystalline, and does not appear immediately, but is 
thrown down on stirring the liquid strongly, and soonest upon the lines, which 
have been described on the glass by the stirrer. A similar precipitation is oc- 
casioned in salts of potash by hyperchloric acid. Also by chloride of pla- 
tinum, which forms the double chloride of platinum and potassium, in glandu- 
lar octohedrons of a pale yellow colour. In the separation of potash, for its 
quantitative estimation, the last reagent is preferred, and is added in ex- 
cess to the potash solution, together with a few drops of hydrochloric acid, 
which is then evaporated by a steam heat to dryness. Water with an 



POTASH. 317 

admixture of alcohol is digested upon the dry residue, which dissolves up 
every thing except the double chloride of platinum and potassium. Ammonia 
is also thrown down by chloride of platinum ; but when the chloride of platinum 
.and ammonium is heated to redness, nothing is left except spongy platinum, 
while the chloride of platinum and potassium leaves all its potassium in the state 
of chloride mixed with the platinum. Potash is likewise separated from acids, 
by means of fluosilicic acid, which throws down a light gelatinous precipitate 
the double fluoride of silicon and potassium. 

Potash is the base which in general exhibits the highest affinity for acids ; it 
precipitates lime and the insoluble metallic oxides from their solutions in acids. 
This alkali is employed indifferently with soda for a variety of useful purposes. 
The principal combinations of potash with acids will be described after the bi- 
nary compounds of potassium. 

Peroxide of potassium, K0 3 . — Heated strongly in air or oxygen, potassium 
combines with three equivalents of oxygen. The ultimate residue on calcining 
nitrate of potash at a red heat has been said to be the same compound, but 
Mitscherlich finds that residue to be potash. The peroxide of potassium is de- 
composed by water, being converted into hydrate of potash, with evolution of 
oxygen gas. 

When potassium is burned with an imperfect supply of air, a gray matter is 
formed, which Berzelius believes to be a sub-oxide of potassium. It is not more 
stable than the peroxide. 

Sulphur et$ of potassium. — Sulphur and potassium, when heated together, 
unite with incandescence, and in several proportions, two of which correspond 
respectively with the protoxide and peroxide of potassium. The protosulphuret 
may be obtained by transmitting hydrogen gas over sulphate of potash, heated 
in a bulb of hard glass to full redness, when the whole oxygen of the salt is 
carried off as water, and the sulphur remains in combination with potassium, 
forming a fusible compound of a light brown colour. Sulphate of potash cal- 
cined with one fourth of its weight of pounded charcoal or pit coal, in a covered 
cornish crucible, at a bright red heat, is converted into a black crystalline mass, 
which is also protosulphuret of potassium, with generally a small quantity of a 
higher sulphuret, arising from the combination of the silica of the crucible with 
potash of the sulphate. If lamp-black be used instead of charcoal, the sulphuret 
of potassium formed having a great affinity for oxygen, and being in a highly 
divided state, takes fire, when exposed to the air, and forms a pyrophorus. The 
solution of the protosulphuret in water is highly caustic ; it is decomposed by 
acids with effervescence, from the escape of sulphuretted hydrogen gas, but 
without any deposite of sulphur. Being a sulphur base, it combines without 
decomposition with sulphur acids, 

This sulphuret unites directly with sulphuretted hydrogen ; and the same 
compound may be otherwise formed, namely, by transmitting a stream of sul- 
phuretted hydrogen through caustic potash, so long as the gas is absorbed. It 
is often named the bihyilrosulphuret of potash. It is analogous- in composition 
to hydrate of potash in the oxygen series. 

The Trilo sulphuret is formed when anhydrous carbonate of potash, mixed 
with half its weight of sulphur, is maintained at a low red heat so long as car- 
bonic acid gas comes off. Of four proportions of potash, three become sulphu- 
ret of potassium, while sulphuric acid is formed which neutralizes the fourth 
proportion of potash: 4KO and 10S == 3 KS 3 and KO, S0 3 . With carbo- 
nate of potash and sulphur, in equal weights, a similar action occurs, at a 
temperature above the fusing point of sulphur, but five, instead of three, pro- 
portions of sulphur then unite with one of potassium, and a Pentasulphuret 
is formed. With a larger proportion of carbonate of potash the same sulphuret 
is also produced, provided. the temperature does not much exceed the boiling point 

27* 



318 POTASSIUM. 

of sulphur, and the excess of carbonate fuses along with it, without undergoing 
decomposition. A sulphuret obtained by fusing sulphur and carbonate of pot- 
ash together has a liver-brown colour, and hence its old pharmaceutic name 
Hepar su/phuris. The three sulphurets described are deliquescent, and are all. 
soluble in water, the higher sulphurets giving red solutions. They may indeed 
be prepared by boiling sulphur, in proper proportions, with caustic potash. A 
simultaneous formation of hyposulphurous acid then occurs, as already ex- 
plained (page 241.) The preparation, Precipitated sulphur, is obtained by 
adding an excess of hydrochloric acid to these solutions, when much sulphur 
is thrown down, although the potassium be only in the state of protosulphuret, 
for the sulphuretted hydrogen arising from the action of the acid on that sul- 
phuret, meets sulphurous evolved at the same time from the decomposition of 
hydrosulphurous acid, and these gases mutually decompose each other, with the 
formation of water and sulphur. The excess of sulphur in the alkaline sulphuret 
also precipitates at the same time. The peculiar whiteness of precipitated sul- 
phur is owing, according to Rose, to its containing a little persulphuret of 
hydrogen. 

Chloride of potassium; KC1; 932.6 or 74.7. — Formed by the combustion 
of potassium in chlorine, or by neutralizing hydrochloric acid by potash or 
its carbonate. It is also derived in considerable quantity from kelp (page 
276.) It crystallizes in cubes and rectangular prisms, resembles common salt 
in taste, is soluble in 3 times its weight of water at 60°, and in less at 212°. 
When pulverized and dissolved in 4 times its weight of cold water, it pro- 
duces a depression of temperature of 20£ degrees; while chloride of sodium, 
dissolved in the same manner, lowers the temperature only 3.4 degrees. 
Upon the difference between the two salts in this property is founded a rude 
mode of estimating their proportions in a mixture. Chloride of potassium is 
principally consumed in the manufacture of alum. 

Iodide of potassium; IK; 2069.5 or 165.87. — This salt is obtained by dis- 
solving iodine in solution of potash till neutral, evaporating to dryness, and 
heating to redness, to decompose the portion of iodate of potash formed. It 
is more soluble than the chloride, and may be obtained in cubes or rectangular 
prisms, which are generally white and opaque, and have an alkaline reaction 
from the presence of a trace of carbonate of potash. The dry salt does not 
combine with more iodine, but in conjunction with a small quantity of water, 
(I believe 4 equivalents) it absorbs the vapour of iodine with great avidity, 
and runs into a liquid of a deep red, almost black, colour. According to Baup, 
a saturated solution of iodide of potassium may dissolve so much as two equi- 
valents of iodine, but allows one equivalent to precipitate when diluted. Iodide 
of potassium is much used in medicine; it is not poisonous in doses of one or 
two drachms. Its solution is also employed as a vehicle for iodine itself, 20 
grains of iodine, and 30 grains of iodide of potassium being usually dissolved 
in 1 ounce of water. The bromide of potassium is capable of dissolving bro- 
mine, but the solution of chloride of potassium has no affinity for chlorine. 

Ferrocynnide of potassium, Yellow prussiate of potash; K 2 ,FeCy 3 -f 3HO? 
2308.7 + 337.5 or 185 + 27.— This important salt is formed when carbonate of 
potash is fused in an iron pot with animal matter, such as dried blood, hoofs, 
clippings of hides, &c, and is the product of a reaction 
Fig. 92. to be hereafter described. This salt occurs in a state of 

great purity in commerce. It is of a lemon yellow co- 
lour, and crystallized in large quadrangular tables, with 
truncated angles and edges, belonging to the square pris- 
matic system. The crystals contain 3 equivalents of 
water, which they lose at 212°, are soluble in 4 parts of 
cold and 1 2 parts of boiling water, and are insoluble in al- 
cohol. The taste of this salt is saline, and it is not poi- 




I 

CYANIDE OF POTASSIUM. 319 

sonous. By a red heat it is converted, with escape of nitrogen gas, into car- 
buret of iron and cyanide of potassium; but with exposure to air the latter salt 
absorbs oxygen, and becomes cyanate of potash. This salt is represented by 
Liebig as containing a salt-radical, Ferrocyanogen, composed of 1 eq. of iron 
and 3 eq. of cyanogen, or FeCy 3 . This imaginary radical is bibasic, and is 
in combination with 2 eq. potassium in- the salt, as will be seen by reference 
to its formula. The same salt has been represented by myself as a compound 
of a tribasic salt-radical prussine (3Cy) with Fe-f 2K. But its reactions with 
other salts are most easily stated on the former view of its constitution. The 
iron in this salt is not precipitated by alkalies. When ferrocyanide of potas- 
sium is added to salts of lead and various other metallic solutions, it produces 
precipitates, in which two atoms of the lead or other metal are substituted, in 
combination with ferrocyanogen, for the two atoms of potassium. In salts of 
peroxide of iron, ferrocyanide of potassium produces the well known precipi- 
tate prussian blue. 

Ferricyanich of potassium, Bed prussiate of potash; 3K, Fe 2 Cy 6 ; 4127.6 
or 331.74. — This salt, which like the last, is a valuable re-agent, is formed by 
transmitting chlorine gas through a solution of the ferrocyanide of potassium, 
till it no longer gives a precipitate of prussian blue with a persalt of iron. 
One fourth of the potassium of the ferrocyanide is converted into chloride, 
from which the resulting ferricyanide may be separated by crystallization. It 
forms right rhombic prisms, which are transparent and of a fine red colour. 
The crystals are anhydrous, soluble in 3.8 parts of cold, and in less hot water. 
They burn with brilliant scintillations when held in the flame of a candle. 
The solution of this salt is a delicate test of iron in the state of protoxide, 
throwing down from its salts a variety of prussian blue, in which the 5K of 
the formula are replaced by 3Fe. Liebig views this salt as containing a salt- 
radical, Ferr icyanogen or ferrideyanogen, Fe 2 Cy e , differing from ferrocya- 
nogen in having twice its atomic weight and being tribasic. 

Cyanide of potassium; KCy, 819.8 or 65.69. — The preparation of this salt 
is attended with difficulty, owing to the action of the carbonic acid of the air 
upon its solution, which evolves hydrocyanic acid, and the tendency of the solu- 
tion itself to undergo spontaneous decomposition, even in close vessels. It may 
be formed by adding absolute hydrocyanic acid, or a strong solution of that 
acid, to a solution of potash in alcohol; a portion of the cyanide falls down as 
a white crystalline precipitate, which should be washed with alcohol and dried, 
and an additional quantity is obtained by evaporating the liquid in a retort. 
But it is prepared with more advantage from the ferrocyanide of potassium 
already described. That salt is carefully dried and reduced to a fine powder, 
which is exposed to a strong red heat in a well closed iron crucible, or other 
convenient vessel, and then allowed to cool completely without exposure to 
air. The porous, semifused mass, which is a mixture of cyanide of potassium 
and carburet of iron, is reduced to a fine powder, placed in a funnel, moistened 
with a little alcohol, and then washed with cold water. The first strong solu- 
tion of cyanide of potassium which comes through is colourless, and must be 
rapidly evaporated to dryness in a porcelain basin, and fused at a red heat. 
Or, alcohol of sp.^r. 0.896 (60 per cent.) may be boiled upon the black mass, 
and dissolves a large quantity of cyanide, the greater proportion of which it 
deposites again on cooling, a property peculiar to alcohol of the strength pre- 
scribed. The application of hot water to the black mass is to be avoided, as 
with access of air, it. causes the reproduction of the ferrocyanide, which im- 
mediately colours the solution yellow (Liebig.*) 

* [ Cyanide of potassium ma)' be obtained sufficiently pure for most of the objects for 
which it is used, and with much greater facility by the following process: — Dry perfectly 
on a hot plate eight parts of ferrocyanide of potassium, powder and mix intimately with 
three parts of carbonate of potassa.. Throw the mixture into a red hot crucible and con- 



320 POTASSIUM. 

The cyanide of potassium crystallizes in colourless cubes, which become 
opaque and deliquesce in damp air, and are very soluble in water. It bears a 
red heat without decomposition in close vessels, but with exposure to oxygen 
becomes cyanate of potash (KO, CyO.) Its solution smells of hydrocyanic 
acid, being decomposed by carbonic acid. The action of cyanide of potassium 
upon the animal economy is equally powerful with that of hydrocyanic acid, 
and as the dry salt may be preserved in a well stopped bottle without change, 
it is preferable to the acid, which is far from stable. Red oxide of mercury 
dissolves freely in the solution of cyanide of potassium, cyanide of mercury 
being formed and potash set free. The purity of the alkaline cyanide may 
be ascertained from this property; 12 grains of the pure cyanide dissolving 20 
grains of finely pulverized oxide of mercury.* 

Hydrocyanic acid for medical purposes is conveniently prepared from this 
cyanide. 24 grains of cyanide of potassium, 56 grains of tartaric acid in crys- 
tals, and 1 ounce of water are agitated together in a stout phial closed by a 
cork. The liquid is afterwards separated by filtration from the precipitate of 
bitartrate of potash; it contains 10 grains of hydrocyanic acid, or rather more 
than 2 per cent. (Dr. Clark.) 

- Sulphocyanide of potassium; K, CyS 2 ; 1222.2 or 97.92.— Sulphocyanogen 
is a salt-radical consisting of two of sulphur and one of cyanogen, which is 
formed on fusing the ferrocyanides with sulphur. To obtain it in combina- 
tion with potassium, the ferrocyanide of potassium, made anhydrous by heat 
and reduced to a fine powder, is mixed with an equal weight of floWers of 
sulphur, in a common cast iron pot (pitch pot,) and kept in a state of fusion 
for half an hour at a temperature inferior to that at which the sulphur would 
boil and bubbles of gas escape through the melted mass. No cyanogen is 
evolved or decomposed, and the residuary matter is a mixture of sulphocyanide 
of potassium and protosulphocyanide of iron, with the excess of sulphur. 
Both sulphocyanides dissolve in water, and give a solution which is colourless 
at first, but soon becomes red from oxidation of the sulphocyanide of iron, 
To get rid of the iron, carbonate of potash is added to the boiling solution, so 
long as a precipitate of carbonate of iron falls, and the liquid is afterwards 
filtered. This solution gives crystals of sulphocyanide of potassium, when 
evaporated, which may be freed from any adhering carbonate of potash, by 
dissolving them in alcohol. The salt crystallizes in long white striated prisms, 
which are anhydrous, and resemble nitrate of potash in their appearance and 
taste. They deliquesce in a damp atmosphere, and are very soluble in hot 
alcohol, from which the salt crystallizes on cooling. The sulphocyanide of 
potassium communicates a blood red colour to solutions of salts of peroxide 
of iron, and is consequently employed as a test of that metal in its higher 
state of oxidation. The red solution is made perfectly colourless by a mode- 
rate dilution with water, when the iron is not present in excess. The sulpho- 
cyanide of potassium has been detected in the saliva of man and the sheep. 

tinue the heat until effervescence ceases, and the fused mass becomes clear and colourless, 
and on the introduction of a glass rod. the portion adhering when withdrawn, on cooling, 
exhibits a crystalline mass of a brilliant white colour. During- the fusion brown flocculi 
may be seen in the liquid, which when the crucible is withdrawn from the fire gradually 
settle to the bottom, and the clear liquid may be decanted without admixture with the 
brown powder. 

The result of the decomposition is a mixture of cyanide of potassium and cyanate of 
potassa, with metallic iron (the brown powder.) The clear fused mass separated from the 
sediment contains five equivalents of cyanide to one of cyanate, or little less than four- 
fifths by weight of cyanide of potassium. — Liebig, Journ. de Pharm. and de Chim., and 
Am. Journ. of Pharmacy. Jan. 1843. R. B.] 

* [Cyanide of potassium in solution has the power of dissolving several other metallic 
oxides besides the oxide of mercury. It will hence remove, in a rapid manner, stains pro 
duced by solutions of gold, silver or copper. R. B.j 



CARBONATE OF POTASH, 



321 



SALTS OF POTASH. 



Carbonate of potash; KO, C0 2 ; 866.4 or 69.43. — This useful salt is princi- 
pally obtained from the ashes of plants. Potash is always contained in a state 
of combination in clay and other minerals which form the earthy part of soil, 
and appears to be a constituent of soil essential to vegetation. The alkali is 
appropriated by plants, and is found in their sap combined with vegetable acids, 
particularly with oxalic and tartaric acids ; also with silicic and sulphuric acids, 
and as chloride of potassium. When the plants are dried and burned, the salts of 
the vegetable acids are destroyed, and leave carbonate of potash ; shrubs yield- 
ing three, and herbs five times as much saline matter as trees ; and the branches 
of trees being more productive than their trunks, a distribution which may 
depend upon the potash existing chiefly in the sap. The whole ashes from 
wood seldom exceed 1 per cent, of its weight, of which l-6th may be saline 
matter. The solution evaporated to dryness yields Potashes, and these partially 
purified and ignited in contact with air form Pearlash. The carbonate is 
mixed in the latter with about 20 per cent, of foreign salts, principally sulphate 
of potash and chloride of potassium. The carbonate of potash is obtained in a 
state of greater purity by dissolving pearlash in an equal weight of water, then 
separating the solution from undissolved salts, and evaporating it to dryness. 

Carbonate of potash is prepared of greater purity for chemical purposes by 
igniting bitartrate of potash, or better by burning together 2 parts of that salt 
and 1 of nitre. In the latter process the carbon and hydrogen of the tartaric 
acid are destroyed by the oxygen of the nitric acid, and carbonate of potash 
remains mixed with charcoal, from which it may be separated by solution and 
filtration. 

Carbonate of potash has an acrid, alkaline taste, but is not caustic. It gives 
a green colour to the blue infusion of cabbage. This salt is highly deliquescent, 
and soluble in less than an equal weight of water at 60°. It may be crystallized 
with two equivalents of water. Added to solutions of salts of lime, lead, &c, 
it throws down insoluble carbonates. It is more frequently used than the 
caustic alkali, to neutralize acids and to form the salts of potash. 

Bicarbonate of potash; HO, C0 2 +KO, C0 2 ; 1255.3 or Fig. 93. 

100.61. — Formed by transmitting a stream of carbonic acid 
gas through a saturated cold solution of the neutral carbonate. 
It is soluble in four times its w r eight of water at 60°, and in 
less water at 212°. The solution has an alkaline taste and 
reaction, but is not acrid; it does not throw down magnesia 
from its soluble salts , it loses carbonic acid when evaporated 
at all temperatures, and becomes neutral carbonate. The salt 
contains one proportion of water, which is essential to it, and 
crystallizes well in prisms of eight sides, Fig. 93, having 
dihedral summits. The existence of a sesquicarbonate of potash is doubtful. 



p\ 


T 


t 


» € 


/ 


/ 



Sulphate of potash; KO, S0 3 ; 1091.1 or 87.43. This salt 
precipitates when oil of vitriol is added drop by drop to a con- 
centrated solution of potash. It is generally prepared by neu- 
tralizing the residue, composed of bisulphate of potash, of the 
nitric acid process, (page 217,) and crystallizes in double pyra- 
mids of six faces, Fig. 94, or in oblique four-sided prisms. 
The crystals are anhydrous, unalterable in air, and they decrepi- 
tate strongly when heated ; their density is 2.400. The sulphate 
is one of the least soluble of the neutral salts of potash ; 100 parts 
of water dissolve 8.36 parts of this salt at 32°, and 0:09666 parts 
more for each degree above that point. 



Fig. 94. 





322 POTASSIUM. 

Hydrated bisulphate of potash, or Sulphate of water and potash; HO, S0 3 
-fKO, S0 3 ; 1704.8 or 136.54.— The fusible salt remaining when nitrate of pot- 
Fig. 95. asn is decomposed in a retort by two equivalents of oil 

of vitriol. Below 386.6° (197° cent.,) it is a white 
crystalline mass. This salt is very soluble in water, but 
is partially decomposed by that liquid, and deposites sul- 
phate of potash. It crystallizes from a strong solution 
in rhombohedral crystals, of which the form is identical 
with one of the forms of sulphur. But this salt is 
dimorphous and crystallizes from a state of fusion by heat in large crystals 
which have the form of felspar (Mitscherlich.) It was the only bisulphate of pot- 
ash known before the unexpected discovery of another salt described below. Its 
density is 2.163. The excess of acid in this salt acts upon metals and alkaline 
bases, very much as if it were free. 

Hydrated sesquisulphate of potash; HO,S0 3 -f-2(KO,S0 3 .) — A salt in pris- 
matic needles discovered by Mr. Phillips, and which has also accidentally 
occurred since to M. Jacquelin, It is decomposed by water ; the circumstances 
necessary for its formation are unknown. 

Anhydrous bisulphate of potash; KO+2S0 3 ; 1592.3 or 127.54. — It appears, 
by M. Jacquelin's researches,* that this salt almost uniformly presents itself 
when sulphate of potash, and not less than one and a half equivalents of oil of 
vitriol are dissolved together in distilled water, and the solution evaporated. It 
crystallizes in prismatic needles, of which the density is 2.277, and point of 
fusion 410° (210° cent.) Left in their mother liquor, these crystals gradually 
disappear, and in their place, large rhombohedral crystals of the hydrated bisul- 
phate are formed. The anhydrous salt may be dissolved and crystallized again 
from a quantity of hot water, not more than sufficient for its solution, but is de- 
composed by a larger quantity of water. This sulphate is analogous to the 
bichromate of potash ; the constitution of these anormal salts has already been 
made the subject of remark (page 240.) 

Sulphate of potash combines with hydrated nitric and phosphoric acids, as. 
well as with hydrated sulphuric acid. On dissolving the neutral salt in nitric 
acid, a little nitre and hydrated bisulphate of potash are formed, with a large 
quantity of salt in oblique prisms, of which the formula is HO, N0 5 4-2 (KO, 
S0 3 .) This last salt fuses at 302° (150° cent.;) its density is 2.38 (Jacquelin.) 
The compound with phosphoric acid is formed by dissolving sulphate of potash 
in a syrupy solution of that acid, and crystallizes in oblique prisms of six sides., 
which fuse at 464° (240° cent.,) and of which the density is 2.296 (Jacquelin.) 
Its formula is 3HO,P0 5 -f-2KO, S0 3 . It will be observed that both these com- 
pounds agree with Mr. Phillips's sesquisulphate, in having two of sulphate of 
potash to one of hydrated acid. 

Nitrate of potash, Nitre, Saltpetre; KO, N0 5 ; 1266.9 or 101.53.— Nitric 
acid is formed in the decomposition of animal matters containing nitrogen, when 
they are exposed to air, and are in contact with alkaline substances. It appears 
to be largely produced in this way in the soil of certain districts of India, from 
which nitrate of potash is obtained by lixivation. Nitrous soils always contain 
much carbonate of lime, the debris of tertiary calcareous rocks, in which the 
oxygen and nitrogen of the air unite, according to some, assisted by the porous 
structure of the rock, and under the influence of an alkaline base, so as to gene- 
rate nitric acid without the intervention of animal matter. But this conjecture 
is not founded upon experiment; nor is it a necessary hypothesis, since nitri- 
fiable rocks are never entirely destitute of organic matter. Nitrate of potash is 
also prepared in some countries of Europe, by imitating the natural process, in 

* An. de Ch. et de Ph. t. 70, p. 311. 



GUNPOWDER. 323 

artificial nitre-beds, wherein nitrate of lime is formed, and afterwards converted 
into nitrate of potash by the addition of wood-ashes to the lixivium.* 

Nitrate of potash generally crystallizes in long pjg # 96, 

striated six-sided prisms, fig. 96, is anhydrous, ^^-^^ 

unalterable in the air, fusible into a limpid liquid ; r f r^^T^^. 

by a heat under, redness, in which condition it (Tt^^f^^ '• *^-^>-> 

is cast in moulds, and /orms sal prim el te. Its [U 0«jh*\_^jJv&k\ 

density is 1.933 (Dr. Watson.) According to \^></^ ^"*"^X»] — |fa 
Gay-Lussac 100 parts of water dissolve 13.3 ^" = ^3r^-J ' I "* J 
parts of this salt at 32°, 29 parts at 64.4°, 74.6 ^^^-^cW^^ 

parts at 96.8°, and 236 parts at 206.6°. The ^^1^ 

taste of the solution is cooling and peculiar; it has considerable antiseptic 
properties. Nitre is insoluble in absolute alcohol. 

From the large quantity which nitre contains, and the facility with which it 
imparts that element to combustibles at a red heat, it is much employed in 
making gunpowder and other deflagrating mixtures. An intimate mixture of 
nitre in fine powder with l-3rd of its weight of wood charcoal, when touched 
by a body in ignition, burns with great brilliancy, but without explosion. A 
mixture of 3 parts of nitre, 2 of dry carbonate of potash, and 1 of sulphur, 
forms pulvis fulminans, which heated gently till it enters into fusion, inflames 
suddenly, and explodes with a deafening report. The violence of the explosion 
is caused by the reaction between the sulphur and nitre being instantaneous, 
from their fusion and perfect intermixture, and the consequent sudden formation 
of much nitrogen gas from the decomposition of nitric acid. Gunpowder con- 
tains both sulphur and charcoal, of which the former serves the purpose of ac- 
celerating the process of deflagration and supplying heat, while the latter sup- 
plies much of the gas, to the formation of which the available force of the 
explosion is due. Gunpowder yields about 300 times its volume of gas, mea- 
sured when cold ; but its explosive force is greater than this indicates, from the 
high temperature of the gas, and not less than It, 00 atmospheres. The ordinary 
proportions of gunpowder approach very nearly 1 eq. of nitre, 1 of sulphur, and 
3 of carbon, as will be seen by the following comparison: — 



COMPOSITION OF GUNPOWDER. 



Theoretical Mixture. 

Sulphur . . 11.9 
Charcoal . . Id. 5 
Nitre . . . 74.6 



English. 


Prussia 


12.5 . . 


. . 11.5 


12.5 . . 


. . 13.5 


75.... 


. . 75. 



100. 100. 100. 

By the combustion of the mixture, carbonic acid and nitrogen gases are 
formed, with a solid residue of protosulphuret of potassium. Thus: — 

* The latest writer upon nitrification is Professor Kuhlinan, whose observations and 
original experiments are valuable, but do not lead to any general theory of the process. He 
did not succeed in causing oxygen and nitrogen gases to combine, by means of spongy 
platinum, but he found that, under the influence of that substance, (1°) all vapourizable 
compounds of nitrogen including ammonia, mixed with air, with oxygen, or with an oxi. 
dating gas, change into nitric acid or peroxide of nitrogen; and (2°) that all the vapourizable 
compounds of nitrogen, including nitric acid, mixed with hydrogen or a hydrogenous gas, 
give rise to ammonia. — (Memoirs of the Academy of Sciences of Lille, 1838, and Liebig*s 
Annalen, Vol. 29, p. 272, 1839.) 



324 POTASSIUM. 



DEFLAGRATION OF GUNPOWDER. 

Before Decomposition. After Decomposition 

3 Carbon. 3 Carbon. ^ 3 Carbonic acid. 

Krt * r [6 Oxygen. 
Nitrate of ) ■ kt -z.za~ 



{ 



Pnt^h Nitrogen. Nitrogen. 

Potash, J Potassium< _^^ 

Sulphur. Sulphur ^ ^ Sulphuret of potassium. 

A portion of the potash is always converted into sulphate of potash, which 
must interfere with the exactness of this decomposition. Blasting powder is 
composed of 20 sulphur, 15 charcoal, and 65 nitre; the proportion of sulphur 
being increased, by which a more powerfully explosive mixture is obtained, but 
which is not suitable for fire-arms, as they are injured by an excess of sulphur. 
The most inflammable charcoal is employed in making gunpowder ; which is 
obtained by calcining branches of about 3-4ths of an inch in diameter, in an 
iron retort, for a considerable time, at a heat scarcely amounting to redness, 
and which has a brown colour without lustre. The granulation of gunpowder 
increases its explosive force. A charge is thus made sufficiently porous to al- 
low flame to penetrate it, and to kindle every grain composing it at the same 
time. But still the discharge of gunpowder is not absolutely instantaneous ; 
and it is remarkable that other explosive compounds which burn more rapidly 
than gunpowder, such as fulminating mercury, are not adapted for the move- 
ment of projectiles. Their action in exploding is violent but local ; if substituted 
for gunpowder in charging ordinary fire-arms, they would shatter them to 
pieces, and not project the ball. It is a common practice to mix with the charge 
of blasting powder used in mining, several times its bulk of sawdust, which ren- 
ders the combustion of the powder still slower, but productive of a sustained 
effort, most effectual in removing large masses. 

Chlorate of potash ; KO, C10 5 ; 1532.6 or 122.81. —This salt is the result of 
a reaction between chlorine and potash, which has already been explained 
(page 267.) In the preparation of chlorate of potash a strong solution of two 
or three pounds of carbonate of potash is made, and chlorine passed through it. 
The gas is conducted into the liquid by a pretty wide tube, or better by a tube 
terminated by a funnel, to prevent its being choked by the solid salt which is 
formed. A stage in the process can be observed, before the liquid has discharged 
much carbonic acid, when bicarbonate, chlorate and hypochlorite of potash ex- 
ists together in solution, and a considerable quantity of chloride of potassium is 
deposited. The latter salt is removed, and the current of chlorine continued 
till the liquid, which is often red from hypermanganic acid, becomes colourless 
or yellow, and ceases to absorb the gas. A considerable quantity of chlorate 
of potash is deposited in tabular shining crystals which are purified by solution 
and a second crystallization, and more of the same salt is obtained from the 
liquid evaporated and set aside to crystallize ; the separation of the chlorate from 
chloride of potassium depending upon the solubility at a low temperature of the 
former salt being greatly less than that of the latter. When chlorate of potash 
is prepared upon a still smaller scale, caustic potash may be substituted in the 
preceding process for carbonate. The solution, concentrated by heat, affords 
crystals of chlorate of potash upon cooling. 

Chloride of lime, after it has lost the greater part of its bleaching power by 
keeping, a condition in which it is occasionally met with in commerce, contains 
chlorate of lime, and is available in the preparation of chlorate of potash. The 
solution of the lime salt is boiled for some time, to complete its change into 
chlorate and chloride ; and then is partially decomposed by means of carbonate 



CHLORATE OF POTASH. 325 

of potash, or evaporated with an admixture of chloride of potassium, when 
chlorate of potash crystallizes out, and chloride of calcium remains in solution 
(Lowig.)* 

This salt is anhydrous. It appears in flat crystals of a pearly lustre, of which 
the forms according to Brooke, belong to the oblique prismatic system. Its 
density is 1.989 (Hassenfratz.) It has a cooling disagreeable taste, like that of 
nitre. According to Gay-Lussac, 1 00 parts of water dissolve 3| parts of chlo- 
rate of potash at 32°, 6 at 59°, 12 at 95°, 19 at 120.2°, and 60 at 219.2°, the 
point of ebullition of a saturated solution. This salt fuses readily in a glass re- 
tort or tube, enters into ebullition and discharges oxygen below a red heat. At 
a certain period in the decomposition, when the mass becomes thick, a quantity 
of hyperchlorate of potash is formed but ultimately chloride of potassium is the 
sole residue. 

Chlorate of potash deflagrates with combustibles more violently than the ni- 
trate. A grain or two of it rubbed in a warm mortar, with an equal quantity 
of sulphur, occasions smart explosions, with the formation of sulphurous acid 
gas. Inclosed with a little phosphorus, in paper, and struck by a hammer, it 
produces a powerful explosion ; but this experiment may be attended with dan- 
ger to the operator from the projection of the flaming phosphorus. A mixture 
which, when dry, inflames by percussion, and which is applied to lucifer matches, 
is composed of this salt, sulphur and charcoal. One of the simplest receipts for 
this percussion powder, consists in washing out the nitre from 10 parts of ordi- 
nary gunpowder, with water, and mixing the residue intimately, while still hu- 
mid, with 5i parts of chlorate of potash in an extremely fine powder. This 
mixture is highly inflammable when dry, and dangerous to preserve in that 
state, 

Hyperchlorate of potash ; KO, C10 7 ; 1732.6 or 138.81. — Processes for pre- 
paring this salt have already been described under hy perchloric acid (page 267.) 
It is also formed in a strong solution of chlorate of potash contained in the 
decomposing cell of a voltaic battery, this salt being deposited in small crystals 
upon the zincoid, and no oxygen liberated there. It requires 55 parts of water 
to dissolve it at 59°, but is largely soluble in boiling water. It crystallizes in 
octohedrons with a square base which are generally small : they are anhydrous. 
It deflagrates less strongly with combustibles than the chlorate ; loses oxygen 
at 400°, and is completely decomposed at a red heat, chloride of potassium 
being left. 

Jodate of potash; KO, I0 7 ; 2669.4 or 213.92.— This salt may be formed by 
neutralizing the chloride of iodine with carbonate of potash, instead of carbonate 
of soda (page 280.) It gives small anhydrous crystals which fuse by heat, and 
lose all their oxygen. Iodic acid likewise forms a biniodate and a teriodate of 
potash, according to Serullas.f The biniodate is obtained by adding an addi- 
tional proportion of iodic acid to a solution of neutral iodate saturated at a high 
temperature ; it contains an equivalent of water, but may be made anhydrous 
by a strong heat, according to my own observations. It occurs in prisms with 
dihedral summits, and requires 75 parts of water at 59° to dissolve it. The 

* [Chlorate of potassa may be most conveniently prepared by mixing together, four parts 
of carbonate of potassa and 3 parts of slaked lime, and exposing the mixture to chlorine 
gas. *« This mixture, although quite dry absorbs the gas with prodigious energy, the tern- 
perature rises above 212° and water is freely evolved .*' The chlorine uniting with potas- 
sium and oxygen, form chloride of potassium, and chloric acid, this latter combining with 
undecomposed potassa. The carbonic acid set free is immediately appropriated by the lime, 
and an insoluble carbonate results. The mass acted on by boiling water yields the chloride 
and chlorate which may be separated by evaporation and crystallization. — Graham, Lond. 
Ed. and Dub. Phil. Mag. 1841, and Amer. Journ. of Pharra. p. 347. Jan. 7, 1842. R. B.] 

t Ann. de Ch. et de Phys. t. 43. 
28 



326 sodium. 

teriodate is obtained on mixing a strong acid, such as nitric, hydrochloric or 
sulphuric, with a hot saturated solution of the neutral iodate, and allowing it to 
cool slowly. It crystallizes in rhombohedrons, and requires 25 parts of water 
to dissolve it. 

Serullas has observed that the biniodate of potash has a great disposition to 
form double salts. A compound with chloride of potassium, to which he as- 
signed the formula KC 3 -fKO, I 2 O l0 , is obtained on adding a little hydrochloric 
acid to a solution of iodate of potash, and allowing the solution to evaporate spon- 
taneously. This salt crystallizes well, but afterwards loses its transparency in 
the air. It is decomposed by water, and cannot be formed by uniting its 
constituent salts. Another compound contains bisulphate of potash; KO, 
S 2 O g -f KO, I%0 10 . This salt is obtained from the mother liquor which remains 
in the preparation of the teriodate of potash, after treatment with sulphuric acid. 
When that liquor is evaporated by heat, this salt is deposited in transparent 
regular crystals. Like the preceding salt it is decomposed by water, and can- 
not be formed directly. These two salts and the teriodate of potash merit a re- 
examination, in reference to their containing water as a constituent. 



SECTION II. 

SODIUM. 
Syn. Natrium. Eq. 291 or 23.31; Na. 

Davy obtained this metal by the voltaic decomposition of soda, immediately 
after the discovery of potassium. An intimate mixture of charcoal and car- 
bonate of soda is obtained by calcining acetate of soda, from which sodium is 
commonly prepared, according to the method described for potassium, and 
with greater facility, owing to the superior volatility of this metal. 

Sodium is a white metal having the aspect of silver. Its density is 0.972, 
at 59°, according to Gay-Lussac and Thenard. This metal is so soft, at the 
usual temperature, that it may be cut with a knife, and yields to the pressure 
of the fingers; it is quite liquid at 194°. It oxidates spontaneously in the air, 
although not so quickly as potassium; and when heated nearly to redness takes 
fire and burns with a yellow flame. Thrown upon water, it oxidates with 
great vivacity, but without inflaming, evolving hydrogen gas, and forming an 
alkaline solution of soda. When a few drops only of water are applied to 
sodium, it easily becomes sufficiently hot to take fire. 

As potassium is in some degree characteristic of the vegetable kingdom, so 
sodium is the alkaline metal of the animal kingdom, its salts being found in 
all animal fluids. Both of these elements occur in the mineral world; of the 
two, perhaps, potassium is most extensively diffused; felspar, the most com- 
mon of minerals, containing 12 per cent, of potash, but from the existence 
every where of a soluble compound of sodium, its chloride, the sources of 
that element are the more accessible, if not the most abundant. 

The anhydrous protoxide of sodium and the peroxide are prepared in the 
same manner as the corresponding oxides of potassium, which they greatly 
resemble in properties. The composition of the peroxide of sodium, however, 
is different, being expressed by the formula 2Na-f 30 (Thenard.) It is sup- 
posed by M. Millon to be Na-f 20. 



CHLORIDE OF SODIUM. 



327 



COMPOUNDS OF SODIUiM. 

Soda; NaO; 391 or 31.31. — A solution of soda is obtained by decomposing 
the crystallized carbonate of soda, dissolved in 4 or 5 times its weight of 
water, by means of half its weight of hydrate of lime; the same points being 
attended to as in the preparation of potash. A preference is given to this 
alkali from its cheapness, for most manufacturing purposes, and in the labora- 
tory it may generally be substituted for potash, where a caustic alkali is re- 
quired. On the large scale it is prepared from sails of soda, a carbonate con- 
taining chloride of sodium and sulphate of soda. The solution of soda is pu- 
rified from these salts by concentrating it considerably, upon which the foreign 
salts cease to be soluble in the liquid and precipitate (Mr. W. Blyth.) 

The following table, constructed by Dr. Dalton, exhibits the quantity of 
caustic soda in solutions of different densities: — 



SOLUTION OF CAUSTIC SODA. 





Density of 


Alkali 


Densitv of 


Alkali 




the solution. 


per cent. 


the solution. 


per cent. 




2.00 


77.8 


1.10 


29.0 




1.85 


63.6 


1.36 


26.0 




1.72 


53.8 


1.32 


23.0 




1.63 


46 6 


1 59 


19.0 




1.56 


41.2 


1.23 


16.0 




1.50 


36.8 


1.18 


13.0 




1.47 


34.0 


1.12 


9.0 




1.44 


31.0 


1.06 


4.7 



The solid hydrate of soda [NaO, HO] is obtained by evaporating a solution 
of soda, precisely in the same manner as the corresponding preparation of pot- 
ash. It is soluble in all proportions in water and alcohol. 

Soda is distinguished from potash and other bases by several properties: — 
1st. All its salts are soluble in water, and it is therefore not precipitated by 
tartaric acid, chloride of platinum, or any other re-agent. 2nd. With sul- 
phuric acid it affords a salt which crystallizes in large efflorescent prisms, 
easily recognised as Glauber's salt. 3rd. Its salts communicate a rich yellow 
tint to flame. 

Su/phurets of sodium. — These compounds so closely resemble the sul- 
phurets of potassium as not to require a particular description. The proto- 
sulphuret of sodium crystallizes from a strong solution in octohedrons. This 
salt contains water of crystallization; in contact with air it rapidly passes into 
caustic soda, and the hyposulphite of the same base. 

Chloride of sodium, Sea salt, Common sail; NaCl; 733.6- or 58.78. — So- 
dium takes fire in chlorine gas, and combining with that element, produces 
this salt. The chloride of sodium is also formed on neutralizing hydrochloric 
acid, by soda or its carbonate, and is obtained thus in the greatest purity. 
Sea-water contains 2.7 per cent, of chloride of sodium, which is the most con- 
siderable of its saline constituents (analysis of sea-water at page 201.) Salt 
is obtained from that source in warm climates, as at St. Ubes, in Portugal, on 
the coast of the Mediterranean near Marseilles, and other places where spon- 
taneous evaporation proceeds rapidly; the sea-water being retained in shallow 
basins or canals, on the surface of which a saline crust forms, with the pro- 
gress of evaporation, which is broken and raked out. Sea-water is also eva- 



328 SODIUM. 

porated artificially, by means of culm, or waste coal, as fuel, on some parts 
of the coast of Britain, but as much for the sake of the bittern as of the com- 
mon salt it affords. The evaporation is not carried to dryness, but when the 
greater part of the chloride of sodium is deposited in crystals, the mother 
liquid, which forms the bittern, is drawn off; it is the source of much of the 
Epsom salt and other magnesian preparations of commerce. Other inexhaus- 
tible sources of common salt are the beds of sal-gem or rock salt, which occur 
in several geological formations posterior to the coal, as at Northwich in Che- 
shire, in Spain, Poland, and many other localities. These beds appear to 
have been formed by the evaporation of salt lakes without an outlet, in which 
the saline matter, continually supplied by rivers, had accumulated, till the 
water being saturated, a deposition of salt took place upon the bottom of the 
lake. The salt is sometimes sufficiently pure for its ordinary uses, as it is 
taken from these deposites, but more generally it is coloured brown from an 
admixture of clay, and requires to be purified by solution and filtration. In- 
stead of sinking a shaft to the bed of rock salt, and mining it, the superior 
strata are often pierced by a bore of merely a few inches in diameter, by which 
water is admitted to the bed, and the brine formed drawn off by a pump and 
pipe of copper suspended in the same tubular opening. 

Chloride of sodium crystallizes from solution in water in cubes, and some- 
times from urine and liquids containing phosphates in the allied form of the 
regular octahedron. Its crystals are anhydrous, but decrepitate when heated, 
from the expansion of water confined between their plates. According to the 
experiments of Fuchs, pure chloride of sodium has exactly the same degree 
of solubility in hot and cold water, requiring 2.7 parts of water to dissolve it; 
or 100 parts of water dissolve 37 of salt at all temperatures. The composition 
of such a solution corresponds exactly with 1 eq. of salt to 18 eq. of water. 
Gay-Lussac makes the boiling point of a saturated solution 229.5°, but that 
temperature is too high (I believe,) for a solution of pure chloride of sodium. 
When a saturated solution is exposed to a low temperature, between 14° and 
5°, the salt crystallizes in hexagonal tables, which have two sides larger than 
the others. Fuchs found these crystals to contain 6, and Mitscherlich 4 equi- 
valents of water. If their temperature is allowed to rise above 14°, they 
undergo decomposition, and are converted into a congeries of minute cubes, 
from which water separates. 

Pure chloride of sodium has an agreeable saline taste, deliquesces slightly 
in damp weather, and dissolves largely in rectified spirits, but is very slightly 
soluble in absolute alcohol. Its density is 2.557 (Mohs.) It fuses at a bright 
red heat, and at a higher temperature rises in vapour. It is immediately de- 
composed by oil of vitriol, with the evolution of hydrochloric acid. Besides 
being used as a seasoning for food, chloride of sodium is employed in the pre- 
paration of the sulphate and carbonate of soda. When ignited in contact with 
clay containing oxide of iron, the sodium of this salt becomes soda, and unites 
with the silica of the clay, while the chlorine combines with iron, and is vola- 
tilized. On this decomposition is founded the mode of communicating the 
salt-glaze to pottery: a quantity of salt is thrown into the kiln, where it is con- 
verted into vapour by the heat, and condensing upon the surface of the pottery 
causes its vitrification, which is attended with the formation of hydrochloric 
acid, and perchloride of iron. 

The bromide and iodide of sodium crystallize in cubes, and resemble in pro- 
perties the corresponding compounds of potassium. The other compounds of 
sodium are not of particular interest. 



ALKALIMETRY. 329 



SALTS OF SODA. 




Carbonate of soda,- NaO,C0 2 -f 10HO; 667.34-1125, or 53.47+90.— This 
useful salt is found nearly pure in commerce, in large crystals, which efflorecse 
when exposed to air. These crystals contain 10 equivalents of water, and 
consist in 100 parts, of 21.81 soda, 15.43 carbonic acid, and 62.76 water. 
According to Dr. Thomson, they generally contain about £ per cent, of sul- 
phate of soda, as an accidental impurity. Their form appears to belong to the 
oblique prismatic system. Their density is 1.623; 100 parts of water dissolve 
20.64 of the crystals at 58.25°, and more than an equal weight at „ 
the boiling temperature (Dr. Thomson.) In warm weather the IG * 
carbonate of soda sometimes crystallizes in another form of crys- 
tal, which is not efflorescent, and of which the proportion of water 
is variously stated by Mitscherlich and Thomson at 7 and 8 equi- 
valents. A. third hydrate was obtained by Mohs, on allowing a 
solution of carbonate of soda, saturated between 68° and 86°, to 
cool; which was found to contain 17.74 per cent, of water, a re- 
sult somewhat exceeding 1 equivalent. On evaporating a solution 
of carbonate of soda at the boiling point, the salt precipitates in a 
powder, which contains nearly the same proportion of water. 

This salt has a disagreeable alkaline taste. When heated it 
undergoes the watery fusion; its water is soon dissipated, and a 
white anhydrous salt remains, which again becomes liquid at a 
red heat, undergoing then the igneous fusion. A mixture of carbonate of pot- 
ash and soda is more fusible than either salt separately. 

Carbonate of soda is prepared by a process which will be described imme- 
diately, under the head of sulphate of soda. Much of the carbonate of com- 
merce is not crystallized, but simply evaporated to dryness, and is then known 
as salts of soda. In this form it always contains chloride of sodium, sulphate 
of soda, and often insoluble matter, and varies considerably in value. The 
soda in combination with carbonic acid only, is available in the application 
of the salt as an alkaline substance. The pure anhydrous carbonate of soda 
consists of 58.58 soda and 41.42 carbonic acid, but the best soda-salts of com- 
merce rarely contain so much as 50 per cent, of available soda. The opera- 
tion of ascertaining the proportion of alkali in these salts, and in other forms 
of the carbonate of soda, is a process of importance from its frequent occur- 
rence, and interesting as a method of analysis of easy execution and appli- 
cable to a great variety of substances. I shall therefore describe minutely the 
mode of conducting it. 



ALKALIMETRY. 

The experiment is to find how many measures of a diluted acid are required 
to destroy the alkaline reaction of, and to neutralize 100 grains of a specimen 
of soda-salt. (1) The acid is measured in the alkalimeter, which is a straight 
glass tube, or very narrow jar with a lip, about 5-8ths. of an inch in width, 
and 14 inches in height, mounted upon a foot, as a of figure 98, capable of 
containing at least 1000 grains of water. It is graduated into 100 parts, each of 
which holds ten grains of water. In the operation of dividing such an instru- 

28* 



330 



SODIUM. 



^ 



^J7 



S 



ment it is more convenient to use measures of mercury than water; 135.68 
p IG gg # grains of mercury, being in bulk equal to 

10 grains of water, 678>40 grains will be 
a d, equal to 50 grains of water. A unit mea- 

^x T sure may be formed of a pipette, b in fi- 
gure 98, made to hold the last quantity 
of mercury, into which the metal is 
poured, the opening at the point of the 
pipette being closed by the finger, and 
the height of the mercury in the tube 
marked by a scratch on the glass, made 
by a triangular file. The bulk of twice 
J 3J that quantity of mercury, or 100 water 

grain measures, may likewise be marked 
upon the tube. The former quantity of 
mercury is then decanted from the tube 
into the alkalimeter to be graduated, and 
a scratch made upon the latter at the 
mercury surface: this is 5 of the ten-grain water measures. Another measure 
is added and its height marked; and the same repeated till 20 measures of mer- 
cury in all have been added, which are 100 ten-grain water measures. The 
subdivision of each of these measures into 5 is best made by the eye, and is 
also marked on the alkalimeter. The divisions are lastly numbered, 0, 5, 10, 
&c., counting from above downwards, and terminating with 100 on the sole of 
the instrument. Several alkali meters may be graduated at the same time, with 
little more trouble than one, the measured quantities of mercury being trans- 
ferred from one to the others in succession. The French alkalimeter, d of 
figure 98, is a more convenient instrument to pour from, but it is too fragile for 
common use. 

(2) To form the test acid, 4 ounces avoirdupois of oil of vitriol are diluted 
with 20 ounces of water; or larger quantities of acid and water are mixed in 
these proportions. About fths. of an ounce of bicarbonate of soda is heated 
strongly by a lamp for a few minutes, to obtain pure carbonate of soda; of 
which 17 1 grains are immediately weighed; that quantity, or more properly 
170.6 containing 100 grains of soda. This portion of carbonate of soda is 
dissolved in 4 or 5 ounces of hot water; and the alkalimeter filled up to 0, 
with the dilute acid. The acid is poured gradually into the soda solution, till 
the action of the latter upon test-paper ceases to be alkaline, and becomes 
distinctly acid, and the measures of acid necessary to produce that change ac- 
curately observed. It may probably require about 90 measures. But it is con- 
venient to have the acid exactly of the strength at which 100 measures of it 
saturate 100 grains of soda. A plain cylindrical jar c, of which the capa- 
city is about a pint and a half, is graduated into 100 parts, each containing 
100 grain measures of water, or ten times as much as the divisions of the al- 
kalimeter. The divisions of this jar, however, are numbered from the bottom 
upwards, as is usual in measures of capacity. This jar is filled up with the 
dilute acid to the extent of 90, or whatever number of the alkalimeter divi- 
sions of acid were found to neutralize 100 grains of soda; and water is added 
to make up the acid liquid to 100 measures. Such is the test acid, of w r hich 
100 alkalimeter measures neutralize, and are equivalent to 100 grains of soda; 
or 1 measure of acid to 1 grain of soda. It is transferred to a stock bottle. 
The remainder of the original ddute acid is diluted with water to an equal 
extent, in the same instrument, and added to the bottle. The density of this 
acid is 1.0995 or 1.0998, which is sensibly the same as 1.1. By a curious co- 
incidence, strong oil of vitriol diluted with H times its weight of water, gives 



BICARBONATE OF SODA. 331 

this test acid exactly; but as oil of vitriol varies a little in strength, it is better 
to form the test acid in the manner described, than to trust to that mixture. 
Twenty-one measures of the test acid should neutralize 100 grains of cr. 
carbonate of soda; and 58.5 measures, 100 grains of pure anhydrous carbo- 
nate of soda. 

(3) In applying the test acid, it is poured from the alkalimeter, as before, 
upon 100 grains of the soda-salt to be tested, dissolved in two or three ounces 
of hot water. The salt contains so many grains of soda, as it requires mea- 
sures of acid to neutralize it; and therefore so much alkali per cent. If the 
soda-salt is mixed with insoluble matter, its solution must be filtered before the 
test acid is added to it. In examining a soda-salt which blackens salts of lead, 
and contains both carbonate of soda and sulphuret or sodium, 100 grains are 
tested as above, and the whole alkali in both salts thus determined. A neutral 
solution of chloride of calcium is also added in excess to the solution of a 
second hundred grains; by which the carbonate of soda is converted into chlo- 
ride of sodium, while carbonate of lime precipitates. The filtered liquid is 
still alkaline, and contains all the sulphuret of sodium; the quantity of soda 
corresponding with which is ascertained by means of the test acid. The dif- 
ference between the quantities of alkali observed in the two experiments is the 
proportion of soda present, as carbonate. 

Borax also may be analyzed by the same test acid, and will be found when 
pure to contain 16.37 per cent, of soda. The carbonates of potash may also 
be examined by the same means, but the per centage of alkali must then be 
estimated higher than the measures of acid neutralized, in the proportion of 
the equivalent of soda to that of potash, which are to each other very nearly 
as 39 to 59. The test paper employed in alkalimetry must be delicate. It 
should be prepared on purpose, by dipping good letter-paper several times in a 
filtered infusion of litmus, and drying it after each immersion, till the paper is 
of a deep purple colour. A test paper prepared with cudbear in the same way 
answers still better, but the latter colouring matter is not easily obtained of 
good quality. The operator must also make himself familiar with the dif- 
ference between the slight reddening of his test paper, by carbonic acid, which 
is disengaged, and the unequivocal reddening produced by a strong acid, which 
last is the indication to guide him. 

Bicarbonate of soda; HO, C0 2 +NaOC0 2 ; 1056.2 or 84.64.— This salt is 
prepared by transmitting a stream of carbonic acid through a saturated solution 
of the neutral carbonate ; it is then deposited as a farinaceous powder, but may 
be obtained in crystals from a weaker solution. It requires 13 times its weight 
of cold water to dissolve it. Although containing two equivalents of acid, this 
salt is alkaline to test paper, but its taste is much less unpleasant than the neutral 
carbonate, and indeed is scarcely perceived when combined with a little common 
salt. The proportion of alkali in bicarbonate of soda is 37.0 per cent., but the 
salt of commerce generally contains upwards of 40 per cent., owing to the 
presence of neutral carbonate in the state of protohydrate, which last salt may 
be separated by a small quantity of water. 

The bicarbonate of soda is also obtained otherwise by an interesting reaction. 
Equal weights of common salt and carbonate of ammonia of the shops are taken; 
the former is dissolved in three times its weight of water, and the latter added 
in a state of fine powder to this solution, the w T hole stirred well together, and 
allowed to stand for some hours. The bicarbonate of oxide of ammonium 
present reacts upon chloride of sodium, producing the sparingly soluble bicar- 
bonate of soda, w T hich precipitates in crystalline grains and causes the liquid to 
become thick, and chloride of ammonium (sal-ammoniac,) which remains in 
solution : — 



332 sodium. 

HO, C0 2 +NH 4 0, C0 o and NaCl = 
HO, C0 2 +NaO, C0 2 "and NH 4 CI. 

The solid bicarbonate of soda is separated from the liquid by pressure in a screw- 
press ; but retains a portion of chloride of sodium. Messrs. Hemming and Dyer, 
who first observed this reaction, have proposed to found upon it a process for 
obtaining carbonate of soda from common salt. 

Sesquicarbonate of soda,- 2NaO-f-3C0 2 +4HO; 2061 or 163.15.— This salt 
presents itself occasionally in small prismatic crystals, but cannot be prepared 
at pleasure. It is unalterable in the air, but is decomposed in the dry state, I 
find, by a less degree of heat than the bicarbonate, notwithstanding its contain- 
ing a smaller excess of carbonic acid. The theoretical carbonate of water, 
supposed to resemble the carbonate of magnesia, will be HO, C0 2 , HO+2HO; 
which gives the salt in question, if the last 2HO are replaced by two proportions 
of protohydrated carbonate of soda. Substitutions of this character appear to 
be common, in the formation of double carbonates and oxalates. The bicar- 
bonate of potash may be formed by the substitution of carbonate of potash for 
the first HO, in this carbonate of water, w r hile the other 2HO disappear. This 
salt occurs native in several places, particularly on the banks of the lakes of 
soda in the province of Sukena, in Africa, whence it is exported under the name 
of Trona, in Egypt, Hungary, and in Mexico, and has the same proportion of 
water as the artificial salt. 

Sulphate of soda, Glauber's salt; NaO,SO 3 +10HO; 892.14-1125, or 71.43 
+90. — This salt occurs crystallized in nature, and also dissolved in mineral 
waters, and is formed on neutralizing carbonate of soda by sulphuric acid. But 
it is more generally prepared by decomposing common salt with sulphuric acid, 
as in the process for hydrochloric acid (page 262.) The sulphate of soda 
crystallizes readily in long prisms, of which the sides are often channeled, which 
have a cooling and bitter taste, and contain 55.76 per cent, of water, or 10 
equivalents ; in which they fuse by a slight elevation of temperature, and which 
they lose by efflorescence in dry air. At 32°, 100 parts of water dissolve 5.02 
parts of anhydrous sulphate of soda, 50.65 parts at 91°, which is the tempera- 
ture of maximum solubility of this salt, and 42.65 parts at the boiling tempera- 
ture. In a super-saturated solution of this salt (page 199,) crystals are some- 
times slowly deposited, which are different in form and harder than, Glauber's 
salt ; they contain 8 equivalents of water. A saturated solution of sulphate of 
soda, kept at a temperature between 91° and 104° affords octohedral crystals 
with a rhombic base, which are anhydrous. They are isomorphous with the 
hypermanganate of barytes.* Their density is 2.642. The anhydrous salt 
fuses at a bright red heat, without loss of acid. Sulphate of soda was at one 
time the saline aperient in common use, but is now superseded by sulphate of 
magnesia. It is still, however, combined with the tartrate of potash and soda, 
in Seidlitz powders. 

* Dr. Clark considers this isomorphism not fortuitous, and founds on it an interesting 
speculation respecting the constitution of soda. It leads him to double the atomic weight 
of sodium, or to estimate it at 582, which he represents by So, and to make soda a perox- 
ide, " So " 2 , which like other peroxides unites with as many proportions of acid as it con- 
tains of oxygen, or with two. The relation between the two salts is thus brought out: — 

Hypermanganate of barytes is, .... BaO-{-Mn 2 7 

Or, on the binary theory of salts, .... Ba-|-Mn 2 8 . 

Two atoms of sulphate of soda, on the same theory, are - Na„-4-S 2 8 ; 

Or 2Na being really "So," ..... « So"-j-S 2 8 . 
It will be observed that, as represented by the second and fourth formulae, hypermanganate 
of barytes and sulphate of soda have a similar atomic constitution; they should therefore 
be isomorphous. — (Records of General Science, Vol. IV., page 45.) 



SODA PROCESS. 



333 



PREPARATION OF CARBONATE OF SODA FROM THE SULPHATE. 

The sulphate of soda is chiefly formed, as a step in the process of preparing 
soda from common salt. The same manufacture requires large quantities of 
sulphuric acid, not less than 40,000 tons of sulphur being annually converted 
into that acid in England; and by means of the acid, 50,000 tons of salt con- 
verted into sulphate of soda. From the last, upwards of 50,000 tons of soda 
ash, and 20,000 tons of crystallized carbonate of soda were manufactured, in 
1838 ; and the manufacture is greatly on the increase.* 

A reverberatory furnace is employed in soda-making and various other 
chemical manufactures, to afford the means 
of exposing a considerable quantity of ma- 
terials to a strong heat, of which a perpendi- 
cular and a horizontal section are given in 
figure 99. It consists of a fire-place a, in 
which the fuel is burned, of which b is the 
ash-pit, with a horizontal flue expanded into 
a small chamber or oven d d, which is raised 
to a strong red heat, by the reverberation on 
its walls of the flame, or heated air from the 
fire, on its passage to the chimney. The 
matters to be heated are placed upon the floor 
of this chamber. It has an opening i in the 
side, for the introduction of materials, and «j 
another opening g at the end most distant 
from the fire ; the chimney is provided with a 
damper p, by which the draught is regulated. 

(1) The sulphate of soda is prepared by throwing 600 pounds of common 
salt into the chamber of the furnace, already well heated, and running down 
upon it from an opening in the roof, an equal weight of sulphuric acid of density 
1.600, in a moderate stream. Hydrochloric acid is disengaged and carried up 
the chimney, and the conversion of the salt into sulphate of soda is completed 
in four hours. (2) The sulphate thus prepared is reduced to powder and mixed 
with an equal weight of ground chalk, and half its weight of small coal ground 
and sifted. This mixture is introduced into a very hot reverberatory furnace, 
about two hundred weight at a time. It is frequently stirred until it is uni- 
formly heated. In about an hour it fuses, is then well stirred for about five 
minutes, and drawn out with a rake into a cast iron trough, in which it is 
allowed to cool and solidify. This is called ball soda or British barilla, and 
contains about 22 per cent, of alkali. (3) To separate the salts from insoluble 
matter, the cake of ball soda, when cold, is broken up, put into vats, and covered 
by warm water. In six hours the solution is drawn off from below, and the 
washing repeated about eight times, to extract all the soluble matter. These 
liquors being mixed together are boiled down to dryness, and afford a salt 
which is principally carbonate of soda, with a little caustic soda and sulphuret 
of sodium. (4) For the purpose of getting rid of the sulphur, the salt is mixed 
with one-fourth of its bulk of sawdust, and exposed to a low red heat in a re- 
verberatory furnace about 4 hours, which converts the caustic soda into car- 
bonate, while the sulphur also is carried off. This product contains about 50 
per cent, of alkali, and forms the soda-salt of best quality. (5) If the crystallized 
carbonate is required, the last salt is dissolved in water, allowed to settle, and 
the clear liquid boiled down until a pellicle appears on its surface. The solution 




Information supplied by Mr. Muspratt of Liverpool. 



334 



SODIUM. 



is then run into shallow boxes of cast iron to crystallize, in a cool place ; and 
after standing for a week the mother liquor is drawn off, the crystals drained, 
and broken up for the market. (6) The mother liquor, which contains the 
foreign salts, is evaporated to dryness for a soda salt, which serves for soap or 
glass making, and contains about 30 per cent, of alkali. 

The most essential part of this process is the fusion of sulphate of soda with 
coal and carbonate of lime ; by the first, the sulphate is converted into sulphuret 
of sodium (page 317,) and by the second the sulphuret of sodium is converted 
into carbonate of soda ; and, if desirable, these changes may be effected sepa- 
rately, by calcining the sulphate with coal and carbonate of lime in succession. 
The lime becomes at the same time sulphuret of calcium, a compound which 
would destroy the carbonate of soda, if dissolved along with that salt, in the 
subsequent lixiviation of the ball soda. But although possessed of a certain 
degree of solubility, the sulphuret of calcium does not dissolve in the experiment, 
from being in combination with lime, as an oxisulphuret of calcium. Hence an 
excess of lime is necessary in the process. The application, however, of very 
hot water to the ball soda is to be avoided, as the oxisulphuret is decomposed 
at a high temperature, and sulphuret of calcium dissolved out. The following 
diagram will represent the chemical changes in this process, supposing for sim- 
plicity that charcoal is employed instead of coal, and lime instead of its carbo- 
nate ; the numbers denoting equivalents : — 



REACTION m THE SODA PROCESS. 

Before decomposition. After decomposition. 

4 Carbon 4 Carbon ' _^~~~ 4 Carbonic oxide. 

Sulphate | 4 ° x JS en 
of Soda- 1 Sodium - 
(^ Sulphur 

Lime S 0x ^ en 

I Calcium ^^ Sulphuret of calcium 

Lime Lime Lime 




The soda derives carbonic acid from the carbonate of lime or from the fire, 
and is therefore obtained principally as carbonate. 

The insoluble oxisulphuret of calcium of this process is known as soda- waste. 
It has hitherto been not merely valueless but troublesome to the manufacturer. But 
the attempt is at present made to turn it to account as a source of sulphur. Means 
are taken to condense the hydrochloric acid, formerly sent up the chimney, and 
this acid is applied to the soda- waste, from which it disengages sulphuretted hy- 
drogen, and carbonic acid. But hydrochloric acid is not produced, in the soda 
process, in adequate quantity for this application of it, and carbonic acid evolved 
with sulphuretted hydrogen might interfere with the combustion of the latter. 
These difficulties, however, are in a great degree removed by the discovery of 
Mr. Gossage, that sulphuret of calcium, when moistened, is decomposed easily 
and completely by a single equivalent of carbonic acid. Hence the application 
of hydrochloric acid to the waste may be made, with the evolution of nothing 
but sulphuretted hydrogen ; and the deficiency in the quantity of hydrochloric 
acid may be made up by a supply of carbonic acid, to be applied to the waste, 
from any other source. The sulphuretted hydrogen is burned, instead of sul- 
phur, in the leaden chamber, to reproduce sulphuric acid. 

Many changes have been proposed upon the soda process. Sulphate of iron, 
produced by the oxidation of iron-pyrites, is a cheap salt, and may be applied 
to convert chloride of sodium into sulphate of soda, — (1) by igniting a mixture 



PHOSPHATE OF SODA. 335 

of these salts in a reverbatory furnace, when sulphate of soda, peroxide of iron 
and volatile perchloride of iron are produced : (2) by dissolving the salts together 
in water, and allowing the solution to fall to a low temperature, when sulphate 
of soda crystallizes, and chloride of iron remains in solution (Mr. Phillips ;) 
or (3) by concentrating the last solution at the boiling point, when the same 
decomposition occurs, anhydrous sulphate of soda precipitates, and may 
be raked out of the liquor. Sulphate of magnesia has also been substituted 
for sulphate of iron in these three modes of application. It has been pro- 
posed, instead of furnacing the sulphate of soda, to decompose it by caustic 
barytes. Chloride of sodium has also been decomposed by moistening it, 
and rubbing it in a mortar with 4 or 6 times its weight of litharge, when an 
oxichloride of lead is formed, and caustic soda liberated. The decomposition 
of chloride of sodium by the carbonate of ammonia, with formation of bicar- 
bonate of soda has already been noticed (page 331.) It appears, however, that 
the soda process first described, which was invented towards the end of last 
century by Leblanc, is still generally preferred to all others. 

The old sources of carbonate of soda, namely ba rilla, or the ashes of the sal- 
sola soda, which is cultivated on the coasts of the Mediterranean, and kelp, the 
ashes of sea-weeds, have ceased to be of importance, at least, in England. 
Barilla contains about 18, and kelp about 2 per cent., of alkali. 

BimJphate of soda; HO,S0 3 + NaO,S0 3 ; 1505.7 or 120.64. This salt is 
obtained in large crystals on adding an equivalent of oil of vitriol to sulphate of 
soda, and evaporating the solution till it attains the degree of concentration 
necessary for crystallization. If half an equivalent only of oil of vitriol is added, 
a sesquisulphate of soda is obtained in fine crystals, according to Mitscherlich. 
Nitrate of soda; NaOJYO. ; 1067.9 or 85.57.— This salt crystallizes in the 
rhomboidal form of calc-spar. It is soluble in twice its weight of cold water, 
and has a tendency to deliquesce in damp air. It burns much slower with com- 
bustibles than nitrate of potash, and cannot therefore be substituted for that salt 
in the manufacture of gunpowder. It is now generally had recourse to, as the 
source of nitric acid. Nitrate of soda is found abundantly in the soil of some 
parts of India ; and at Atacama in Peru, it covers large districts, from which it 
is exported in considerable quantity. 

Chlorate of soda (NaO,C10 s ) is formed by mixing strong solutions of bitar- 
trate of soda and chlorate of potash, when the bitartrate of potash precipitates, 
and the chlorate of soda remains in solution. It crystallizes in fine tetrahedrons, 
and is considerably more soluble than chlorate of potash. 

Phosphates of soda.— There are three crystallizable phosphates of soda be- 
longing to the tribasic class, which I shall describe under their old names. 

Phosphate of soda; HO,2XaO,P0 5 -4-24HO ; 4486.6 or 359.15.— This is the 
salt known in pharmacy as phosphate of soda, and formed by neutralizing phos- 
phoric acid from burnt bones (page 251) with carbonate of soda. It crystal- 
lizes in oblique rhombic prisms, which are efflorescent, and essentially alkaline. 
The taste of phosphate of soda is cooling and saline, and less disagreeable than 
sulphate of magnesia, for which it may be substituted as an aperient. It dis- 
solves in 4 times its weight of cold water, and fuses in its water of crystallization, 
when moderately heated. When evaporated above 90° this salt crystallizes in 
another form with 14 instead of 24 atoms of water (Clark.) It is deprived of 
half its alkali by hydrochloric acid, but not by acetic acid. 

Subphosphate of soda ; 3NaO,P0 5 -f24HO : 4764.5 or 381.78.— Formed 
when an excess of caustic soda is added to the preceding salt. It crystallizes 
in slender six-sided prisms with flat terminations, which are unalterable in air ; 
but the solution of this salt rapidly absorbs carbonic acid, and is deprived of 
one-third of its alkali by the weakest acids. The crystals dissolve in 5 times 



336 sodium. 

their weight of water at 60°, and undergo the watery fusion at 170°. This salt 
continues tribasic after being exposed to a red heat. 

Biphosphate of soda ; 2HO,NaO,P0 5 -f 2HO; 1733.1 or 1 38.88.— Obtained by 
adding tribasic phosphate of water to phosphate of soda, till the latter ceases to 
produce a precipitate with chloride of barium. The solution affords crystals, in 
cold weather, of which the ordinary form is a right rhombic prism, having its larger 
angle of 93° 54'. But this salt is dimorphous, occurring in another right rhombic 
prism, of which the smaller angle is 78° 30', terminated by pyramidal planes iso- 
morphous with binarseniate of soda. The biphosphate of soda is very soluble, 
and has a distinct acid relation. Like all the other soluble tribasic phosphates, 
it gives a yellow precipitate. with nitrate of silver, which is tribasic phosphate 
of silver. 

Phosphate of soda and ammonia, Microcosmic salt ; H0,NH 4 0,Na0,P0 s -f- 
8HO. — This salt is obtained by heating together 6 or 7 parts of crystallized 
phosphate of soda, and 2 parts of water, till the whole is liquid, and then adding 
1 part of powdered sal-ammoniac. Chloride of sodium separates, and the so- 
lution, filtered and concentrated, affords the phosphate in prismatic crystals. It 
is purified by a second crystallization. This salt occurs in large quantity in 
urine. It is much employed as a flux in blow-pipe experiments. By a slight 
heat it loses 8HO, by a stronger heat it is deprived of its remaining water and 
ammonia, and converted into metaphosphate of soda, which is a very fusible 
salt. It will be observed that three atoms of base in this phosphate are all 
different, namely water, oxide of ammonium, and soda ; of which the last two 
belong to the same natural family. This salt, I believe, proved the consti- 
tution of the bibasic and tribasic organic acids by supplying the canon, founded 
upon it by myself, that bases of the same family may exist together in the salts 
of such acids, but not in ordinary double salts ; which was happily applied to 
elucidate the salts of the acids in question by MM. Liebig and Dumas. No 
phosphate exists, corresponding with microcosmic salt, but containing potash 
instead of oxide of ammonium ; the phosphate of soda, with 14HO, has been 
mistakenfor such a salt. 

Pyrophosphate of soda-, 2NaO,PO 5 -f-10HO; 1674.1 = 1125, or 134.15 -f 90. 
— Procured by heating the phosphate of soda to redness, when it loses its basic 
water as well as its water of crystallization. The residual mass dissolved in 
water affords a salt, which is less soluble than the original phosphate, and crys- 
tallizes in prismatic crystals, which are permanent in air, and contain ten atoms 
of water. Its solution is essentially alkaline. This salt is precipitated white, by 
nitrate of silver. It is to be remarked that insoluble pyrophosphates, including 
pyrophosphate of silver, are soluble to a considerable degree in the solution of 
pyrophosphate of soda. The pyrophosphates of potash and of ammonia can 
exist in solution, but pass in tribasic salts when they crystallize. 

A bipyro phosphate of soda (HO, NaO, P0 5 ) exists, obtained by the appli- 
cation of a graduated heat to the biphosphate of soda, but it does not crystallize. 
Its solution has an acid reaction. 

Metaphosphate of soda; NaO, P0 5 ; 1283.2 or 102.82.— The three phos- 
phates last described, all contain but one equivalent of fixed base, and afford 
the metaphosphate of soda, when heated to redness; microcosmic salt being 
readily procured, may be recommended for that purpose. The metaphosphate 
of soda fuses at a heat, which does not exceed low redness, and on cooling 
forms a transparent glass, which is deliquescent in damp air, and very soluble 
in water, but insoluble in alcohol; its solution has a feeble acid reaction, which 
can be negatived by the addition of 4 per cent, of carbonate of soda. When 
evaporated, this solution does not give crystals, but dries into a transparent 
pellicle, like gum, which retains at the temperature of the air somewhat more 
than a single equivalent of water. Added to neutral, and not very dilute solu- 
tions of earthy and metallic salts, metaphosphate of soda throws down insolu- 



metaphosphate of soda. 337 

ble hydrated metaphosphates, of which the physical condition is remarkable. 
They are all soft solids, or semifluid bodies; the metaphosphate of lime having 
the degree of fluidity of Venice turpentine. An account has already been 
given of the singular change, at a particular temperature, of hydrated meta- 
phosphate of soda into bipyrophosphate of soda, occasioned by an atom of 
water becoming basic to the acid, which before was constitutional to the salt 
(page 255.) 

The bipyrophosphate of soda undergoes several changes, under the influence 
of heat before it becomes metaphosphate. At a temperature of 500°, the salt 
becomes nearly anhydrous, and affords a solution which is neutral to test pa- 
per, but in other respects resembles the bipyrophosphate. But at temperatures 
which are higher, although short of a red heat, the salt being anhydrous, ap- 
pears to have lost its solubility in water; at least it is not affected at first when 
thrown in powder into boiling water, but gradually dissolves by continued di- 
gestion and passes into the preceding variety. — (Phil. Trans. 1833, p. 275.) 

Borax, Biborate of soda-, NaO,2B0 3 -f 10HO; 1263.3+1125 or 101.23+ 
90. — This salt is met with in commerce in large hard crystals. It is found in 
the water of certain lakes in Transylvania, Tartary, China, and Thibet, and is 
deposited in their beds by spontaneous evaporation. It is imported from India 
in a crude state, and enveloped in a fatty matter, under the name of Tinka/, 
and afterwards purified. But nearly the whole borax consumed in England is 
at present formed by neutralizing with carbonate of soda, the acid from the bo- 
racic lagoons of Tuscany. The ordinary crystals of borax are prisms of the 
oblique system, containing 10 atoms of water, which are not efflorescent al- 
though injured by acid fumes, (Mr. O. Sims;) but it also crystallizes at 133° 
in regular octohedrons, which contain only 5 atoms of water. This salt has a 
sweetish, alkaline taste; for although containing an excess of acid, it has an 
alkaline reaction, like the bicarbonate of soda. 

The anhydrous salt is very fusible by heat, and forms a glass. This glass 
possesses the property of dissolving most metallic oxides, the smallest por- 
tions of which colour it. As the metal may often be discovered by the colour, 
borax is valuable as a flux in blow-pipe experiments. As pieces of metal could 
not be soldered together, if covered by oxide, borax is fused with the solder 
upon the surface of the metals to be joined, to remove the oxide. Borax is 
also a constituent of the soft glass, known as jewellers' paste, which is coloured 
to imitate precious stones. But the most considerable consumption of this 
salt is at the potteries, in the formation of a glaze for porcelain. 

A neutral borate of soda was formed by Berzelius by calcining strongly 
1 eq. of borax with 1 eq. of carbonate of soda, when carbonic acid is expelled. 
The solution yields a salt belonging to the oblique prismatic system, of which 
the formula is, NaO,BO,+8HO. When heated, it fuses in its water of crys- 
tallization, and is expanded into a vesicular mass of extraordinary magnitude, 
by the vaporization of that water. 

When borax is fused with carbonate of soda in excess, the quantity of car- 
bonic acid which escapes indicates the formation of a borate, 3NaO+2B0 3 , 
but which has not been farther examined. 

A salt is said to exist, formed of NaO + 4B0 3 , but to crystallize with diffi- 
culty, formed on combining borax with a quantity of boracic acid equal to 
what it already contains. M. Laurent has also shown that a sexborate of 
soda exists in solution, but is not crystallizable.* The borates of potash 
have also been examined by Laurent, The sexborate crystallizes well; its 
formula is KO,6BO 3 +10HO. A triborate is represented byKO,3B0 3 + 

* An. de Ch. et de Ph. t. 67, p. 218. 
29 



338 sodium. 

8H0; the biborate corresponds in composition with octohedral borax, but has, 
not withstanding, a different and incompatible form. 

Silicates of soda. — When the earth silica (page 231) is thrown into carbo- 
nate of potash or soda, in a state of fusion by heat, a fusible silicate is formed, 
in which, judging from the quantity of carbonic acid expelled, 3 eq. of alkali 
are combined with 2 of silica, or the oxygen in alkali is to that in the silica as 
1 to 2. This silicate dissolves in the clear and liquid carbonate. When on the 
other hand a greater proportion of silica is fused with the carbonate, the whole 
carbonic acid of the latter is expelled, and the excess of silica then dissolves 
in the silicate. The silica and silicate of such mixtures do not separate by 
crystallization, but uniformly solidify together, on cooling, as a homogeneous 
glass, whatever their proportions may be. It is thus impossible to obtain alka- 
line silicates, which, are certainly definite combinations. A mixture of silica 
with potash or soda, in which the oxygen of the former is to that of the latter 
as 18 to 1, is said still to be fusible by the heat of a forge; but when the pro- 
portion is as 30 to 1, the mixture merely agglutinates or frits. These combi- 
nations, even with a large quantity of silica, continue to be soluble in water. 

A compound, known as soluble glass, is obtained by fusing together 8 parts 
of carbonate of soda (or 10 of carbonate of potash) with 15 of fine sand and 
1 of charcoal. The object of the charcoal is to facilitate the combination of 
the silica with the alkali, by destroying the carbonic acid, which it converts 
into carbonic oxide. This glass, when reduced to powder is not attacked by 
cold water, but is dissolved by 4 or 5 parts of boiling water. The solution 
may be applied to objects of wood, and when dried by a gentle heat forms a 
varnish, which imbibes a little moisture from the air, but is not decomposed 
by carbonic acid, nor otherwise alterable by exposure. Stuffs impregnated 
with the solution lose much of their combustibility, and wood is also de- 
fended by it, to a certain degree, from combustion. 



GLASS. 

The alkaline silicates, cooled quickly or slowly, never exhibit a crystalline 
structure, but are uniformly vitreous. They are the bases of the ordinary va- 
rieties of glass, which contain earthy silicates besides, but appear to owe the 
vitreous character to the silicates of potash and soda. The silicate of lime and 
the silicate of the protoxide of iron crystallize on cooling, so does the silicate 
of lead, unless it contains a large excess of oxide of lead. The addition of 
the silicate of potash or soda deprives them entirely of this property: the sili- 
cate of alumina considerably diminishes it. But if silicate of potash or soda 
are heated for a long time, the alkali may in part escape in vapour, and if 
other bases exist in the compound, it then often assumes a crystalline structure 
on cooling. The alkaline silicates by themselves are soluble in water, and de- 
composed by acids; the silicate of lime is also dissolved by acids, but the 
double silicates, on the contrary, resist the action of acids, particularly when 
they contain an excess of silica. The following table exhibits the composi- 
tion of the best known kinds of glass, from the analyses of Dumas and of 
Faraday: — 



GLASS. 



339 



COMPOSITION OF VARIETIES OF GLASS. 



Silica. 



Potash. 



Lime. 



Ox. lead. Alumina. Water 



Bohemian glass 
Crown glass . 
Window-glass 
Bottle glass 
Flint glass . . 
Crystal . . . 
Strass . . . 
Soluble glass . 



12 

22 
11 sods 






10 





3 





7 


ox. iron. 





43 





33 





53 


1 









Silicate of soda and lime. — To form window-glass 100 parts of a quartzy 
sand are taken, with 35 to 40 parts of chalk, 30 to 35 parts of carbonate of 
soda and 180 parts of broken glass. These materials are first fritted, or heated 
so as to cause the expulsion of water and carbonic acid, and to produce an ag- 
glutination of their particles, and afterwards completely fused in a large clay 
crucible of a peculiar construction. For the first formation of the glass a 
higher temperature is required, than that at which it is most thick and viscid, 
and in the proper condition for working it. At the latter temperature, the sub- 
stance possesses an extraordinary degree of ductility, and may be drawn out 
into threads so fine as to be scarcely visible to the eye. A portion of the 
plastic mass, on the extremity of a blow-pipe, may be expanded into a glo- 
bular flask, and pressed or bent into vessels of any form, which may be pared 
and fashioned by the scissors. At a lower temperature, glass vessels become 
rigid, and when cold, brittle in the extreme, unless they be annealed, that is, 
kept for several hours at a temperature progressively lowered from the highest 
degree which the glass can bear without softening, to the temperature of the 
atmosphere. The well-known glass tears, or Prince Rupert's drops, as they 
are also called, which are made by allowing drops of melted glass to fall into 
water, illustrate the peculiar properties of unannealed glass. The surface be- 
coming solid by the sudden cooling, while the interior is still at a high tem- 
perature and consequently dilated, the drop is of greater volume than it would 
be if cooled slowly and equally throughout its mass. Its particles are thus 
in a state of extreme tension, and an injury to any part causes the whole mass 
to fly to pieces. The fracture of unannealed vessels, which is the immediate 
consequence of scratching their surface, has been compared to the effect upon 
a sheet of cloth forcibly stretched, of injuring its edge in the smallest degree 
by a knife or scissors. It then ceases to preserve its integrity by resisting 
the tension, and is torn across. The relative proportions of the ingredients 
of this and other species of glass is subject to some variation. But the oxy- 
gen in the bases of window-glass is to the oxygen of the silica, nearly as 1 to 
4. This glass has a green tint, which is very obvious in a considerable mass 
of it, occasioned in part, it may be, by the impurities of the materials, but a 
certain degree of which appears to be essential to a soda-glass. For in all the 
colourless and finer varieties of glass, it is necessary to use potash. 

Silicates of potash and lime. — Plate-glass used for mirrors, crown-glass, and 
the beautiful Bohemian glass are of this composition. In the most remarkable 
varieties the oxygen of the bases is to that of the acid as 1 to 4, and the oxy- 
gen of the lime to that of the potash in proportions which vary from 1 and f , 
to 1 and 1. This is the glass of most difficult fusibility, and therefore most 
suitable for the combustion tubes employed in organic analysis. From its 
purity, and the absence of oxide of lead, it is also made the basis of most co- 
loured glasses, and of stained glass. To produce coloured glasses certain me- 
tallic oxides are mixed with the fused glass in the pot, oxide of cobalt for 



340 SODIUM. 

instance, for a blue colour, oxide of copper for green, peroxide of manganese 
for purple, and peroxide of uranium for a delicate lemon yellow tint. Arse- 
nious acid and peroxide of tin render glass white and opaque, like enamel. 
In stained glass, on the other hand, the metallic oxides are merely applied 
with proper fluxes to the surface of the glass, which is then exposed in an 
oven to a temperature sufficient to fuse the colouring matter. Different shades 
of yellow and orange are thus produced by means of oxide of silver, and a 
superb ruby red by a proper, but difficult, application of suboxide of copper. 

Silicates of potash and lead. — These substances enter into the composition 
of the purer and more brilliant species of glass in use in this country, such as 
that called crystal, of which most drinking vessels are made, flint-glass for 
optical purposes, and strass, which is employed in imitations of the precious 
stones. For crystal, the materials are taken in the following proportions, 120 
parts of fine sand, about 40 of purified potashes, 35 of litharge or minium, and 
12 of nitre. In this glass, the oxygen of the bases is to that of the silica, as 
1 to a number which may vary from 7 to 9, and the oxygen of the potash is 
to that of the oxide of lead, as 1 to a number varying from 1 to 2.5. In flint- 
glass and in strass, the oxygen of the bases is to that of the silica as 1 to 4, 
and the oxygen of the potash is to that of the oxide of lead as 2 to 3 in flint- 
glass, and as J to 3 in strass, (Dumas.) The more oxide of lead glass con- 
tains, the higher its density; the density of this kind of glass exceeding 3.6, 
while that of the Bohemian glass does not rise higher than 2.4. Glass con- 
taining oxide of lead is recommended by its greater fusibility and softness, 
by which it is more easily fashioned into various forms, and by its great bril- 
liancy, which is remarkable in lustres and other objects of cut glass. The 
presence of lead in glass is at once discovered by its surface acquiring a me- 
tallic lustre when heated to redness in the reducing flame. 

Silicates of alumina, of the oxides of iron, magnesia, and potash or soda. — 
Green or bottle glass, of which wine-bottles, carboys, and glass articles of low 
price consist, is a mixture of these silicates. It is formed of the cheapest 
materials, such as sand, with soap-makers' waste lime that has been used to 
render alkali caustic, &c. In the bottle-glass of this country the small quan- 
tity of alkali is chiefly soda. The alkaline sulphates when fused with silica 
and carbonaceous matter, lose their sulphuric acid, and become silicates; even 
common salt is decomposed by the united action of silica and the aqueous 
vapour in flame, but much of it is lost from its own volatility. The propor- 
tion of silica to the bases is much less in this than in the other kinds of glass, 
the oxygen of the former being to the latter as 2 to 1; and the oxygen of the 
alumina and peroxide of iron equal to that of the potash and lime. This glass 
is in fact a mixture of neutral and subsilicates, and is more apt than any of 
the preceding species to assume a crystalline structure when maintained long 
in a soft condition by heat. A bottle of green glass may be devitrified, or 
converted into what is called Reaumur's porcelain, by enveloping it in sand, 
and placing it where its temperature is kept high for several weeks, as in a 
brick kiln or porcelain furnace. It has been supposed that the glass loses its 
alkali in these circumstances, and is thus more easily crystallized, but the 
proportion of alkali is found undiminished after the change. Glass of all 
kinds, however, when strongly and repeatedly heated loses alkali, from its 
volatility; the glass then becomes harder and less fusible, and is not so easily 
wrought, a circumstance which may sometimes be remarked in blowing a 
bulb upon a tube which has been too long exposed to the blow-pipe flame. 



LITHIUM. 341 

SECTION III. 

LITHIUM. 
Eq. 80.33 or 6.44; L. 

Lithium is the metallic basis of a rare alkaline oxide lithia discovered in 
1818 by Arfwedson.* The name lithia (from ;u0<»«$, stony,) was applied to 
it, from its having been first derived from an earthy mineral. The metal was 
obtained by Davy by the voltaic decomposition of lithia, and observed to be 
white, resembling sodium, and to be highly oxidable. The equivalent of 
lithium is much smaller than that of any other metal, and its oxide has there- 
fore a high saturating power. 

Lithia; LO. — The only known oxide of lithium is a protoxide. It exists 
in small quantities in the minerals spodumene, or triphane, petalite, and lepi- 
dolite, of which the latter can be procured in largest quantity. The separa- 
tion of lithia from this mineral rests upon its decomposition by means of lime 
at a high temperature, and the formation of silicate of lime. By a protracted 
digestion of the ignited mass in boiling lime-water, the liberation of the lithia 
is completed, and it dissolves in that liquid. The oxides in solution are con- 
verted into chlorides, by the addition of hydrochloric acid, and must be sub- 
mitted to several additional operations to separate iron, lime, and potash. 
The chloride of lithium is finally taken up by absolute alcohol, in which the 
chloride of potassium is not soluble. For the necessary directions for con- 
ducting this difficult process, I must refer to Berzelius. — (Traite, t. I p. 303.) 

The hydrate of lithia resembles hydrate of potash in causticity, but is less 
soluble in water, and loses its combined water at an elevated temperature. 
Sulphur acts upon it in the same manner as upon potash. 

The chloride is very soluble in water, as well as in absolute alcohol, and 
fuses at a high temperature. 

The carbonate of lithia has a certain degree of solubility, and its solution 
has an alkaline re-action, properties upon which the claim of lithia to be 
ranked among the alkalies, instead of the alkaline earths, is chiefly rested. 
The fluoride of lithium has the sparing solubility of the carbonate. 

The sulphate of lithia is soluble, and presents itself in fine crystals, which 
are persistent in air. The nitrate and acetate are both very soluble and deli- 
quescent. 

The neutral phosphate of lithia is slightly soluble in water, but considerably 
more so than the double phosphate of lithia and soda, which remains as an 
insoluble powder when the solution of lithia is evaporated to dryness with 
that of phosphate of soda. Hence phosphate of soda is used as a test of lithia. 
The salts of lithia are also recognised, when heated on platinum wire before 
the blow-pipe, by tinging the flame of a red colour. 

* An. de. Ch. et de Ph. t. 10,. 



29 } 



342 BARIUM. 



ORDER II. 

METALLIC BASES OF THE ALKALINE EARTHS. 

SECTION IV. 

BARIUM. 

Eq. 856.9 or 68.66; Ba. 

Barium, the metallic basis of barytes, was obtained by Davy in 1808, by 
the voltaic decomposition of moistened carbonate of barytes in contact with 
mercury; it may likewise be procured by passing potassium in vapour over 
barytes heated to redness in an iron tube, and afterwards withdrawing the re- 
duced barium, which the residue contains, by means of mercury. The latter 
metal is separated by distillation in a retort, care being taken not to raise the 
temperature to redness, for then the barium decomposes glass. Barium is a 
white metal like silver, fusible under a red heat, denser than oil of vitriol in 
which it sinks. It oxidates with vivacity in water, disengages hydrogen, and 
is converted into barytes. It is named barium (from jSae^t/s, heavy,) in allusion 
to the great density of its compounds. 

Barytes or Baryta: BaO; 956.9 or 76.66. — This earth exists in several 
minerals, of which the most abundant are sulphate of barytes or heavy spar, 
and the carbonate of barytes or Witherite. The earth is obtained in the anhy- 
drous condition and pure, by calcining nitrate of barytes, at a bright red heat, 
in a porcelain retort,, or in a well-covered crucible of porcelain or silver, but 
not of platinum. If the calcination is not carried sufficiently far, a combina- 
tion remains of barytes and nitrous oxide (Berzelius,) which has been mis- 
taken for peroxide of barium. The iodate of barytes also may be calcined in 
a porcelain retort, for barytes; it is, T find, more easily decomposed than the 
nitrate, and has not the troublesome property of fusing and swelling up, when 
heated, which the latter salt possesses. The iodine comes off, with oxygen, 
and may be recovered. Iodate of barytes itself is obtained, as an insoluble 
precipitate, on adding chloride of barium to iodate of soda (page 280.) Ba- 
rytes is a gray powder, of which the density is about 4. When heated to 
redness in a porcelain tube, and oxygen passed over it, it absorbs that gas 
with avidity, and becomes peroxide of barium, the compound for the prepara- 
tion of which anhydrous barytes is chiefly required. This earth slakes and 
falls t6 powder, when water is thrown upon it, combining with one equiva- 
lent of water with the evolution of much heat. 

Hydrate of barytes is a valuable re-agent. Of the different processes for 
this substance, one of the most convenient is that from the native sulphate. 
This is a soft mineral and easily reduced to an impalpable powder, which is 
intimately mixed with l-3rd of its weight of coal-dust, or coal pounded and. 



BARYTES. 343 

sifted; the mixture is introduced into a cornish crucible, and exposed in a fur- 
nace to a bright red heat for an hour. The sulphate is converted by this treat- 
ment into sulphuret of barium; the last salt is dissolved out of the black residu- 
ary mass, by boiling water, and the solution, which generally has a yellowish 
tint but is sometimes colourless, is filtered while still hot. The solution, if 
strong, may crystallize on cooling, in thin plates. As it also absorbs oxygen 
from the air, and returns to the state of sulphate of barytes, it must not be ex- 
posed long in open vessels. To a boiling solution of sulphuret of barium in 
a flask, black oxide of copper from the nitrate is added, in successive small 
portions, till a drop of the liquid ceases to blacken a solution of lead, and pre- 
cipitates it entirely white; the liquid then contains only hydrate of barytes in 
solution. It may immediately be filtered, with little access of air, as it ab- 
sorbs carbonic acid. The decomposition in this process, for which we are 
indebted to Dr. Mohr, of Coblentz, is rather complicated. Six eq. of sul- 
phuret of barium and 8 of oxide of copper producing 5 of barytes, 1 of hypo- 
sulphite of barytes, and 4 of subsulphuret of copper: 

6BaS and 8CuO = 5BaO and BaO,S 2 2 and 4Cu 2 S. 

Peroxide of manganese may be substituted in this process for oxide of copper, 
but generally gives a solution of barytes coloured by some impurity. The 
re-action is then similar: * 

6BaS and 4Mn0 2 = 5BaO and BaO,S 2 2 and 4MnS. 

If the solution of sulphuret of barium has been concentrated, the greater part 
of the hydrate of barytes separates on cooling, in voluminous and transparent 
crystals. It is soluble in 3 parts of boiling water, and in 20 parts of water at 
60°. Mr. Smith finds this hydrate to contain 9HO, of which it loses 7, by a 
moderate heat, and 1 additional, by a stronger heat. Barytes retains 1 eq. of 
water with great force like the fixed alkalies. This combination is fusible a 
little below redness, and runs like an oil; it congeals into a crystalline mass, 
which attracts carbonic acid very slowly from air, and is therefore the most 
favourable condition in which to preserve hydrate of barytes. 

The solution of barytes is strongly caustic, although less so than potash or 
soda; and, in common with all the soluble preparations of barium, it is poison- 
ous. It is used to remove carbonic acid from air and other gases (page 209.) 
Barytes, whether free or in combination with an acid, as a soluble salt, is dis- 
covered by means of sulphuric acid, which throws down sulphate of barytes, a 
compound not decomposed by, nor soluble in, nitric and hydrochloric acids. 

Peroxide of barium; Ba0 2 ; 1056.9 or 84.69. — This compound is prepared 
by exposing anhydrous barytes to pure oxygen at a red heat ; or by heating 
pure barytes to low redness in a porcelain crucible, and then gradually adding 
chlorate of potash, in the ratio of about 1 part of the latter to 4 of the former. 
The chloride of potassium is removed, by cold water, from the peroxide of 
barium formed at the same time, while the latter forms a hydrate with 6HO 
(Liebig and Wchler.) Peroxide of barium, when • decomposed by dilute acids 
with proper precautions, affords peroxide of hydrogen. 

Chloride of barium,- BaCl-f-2HO; 1299.6+225, or 104.83+18.— Are-agent 
of constant use, which is obtained by dissolving native carbonate, of barytes in 
pure hydrochloric acid diluted with 3 or 4 times its bulk of water, or by neu- 
tralizing sulphuret of barium by the same acid. It crystallizes from a concen- 
trated solution in flat four-sided tables, bevelled at the edges, very like crystals 
of heavy spar. The crystals contain 2 eq. of water, (14.75 per cent.,) which 
they lose below 212°. They are said to be soluble in 400 parts of anhydrous 

* Liebig's Annalen, v. 27, p. 21. 



344 STRONTIUM. 

alcohol: 100 parts of water dissolve 43.5 at 60°, and 78 at 222°, which is the 
boiling point of the solution. 

Carbonate of barytes; BaO,C0 2 : 1233.3, or 98.83.— This salt consists in 
100 parts of 22.41 carbonic acid, and 77.59 barytes. The density of the native 
carbonate is 4.331. It retains its carbonic acid at the highest temperatures. 
The precipitated carbonate loses its carbonic when calcined at a white heat, in 
contact with carbonaceous matter. It is obtained in greater purity when pre- 
cipitated by the carbonate of ammonia, than by the carbonate of potash or soda, 
portions of which are apt to go down in combination with carbonate of barytes. 
Although reputed an insoluble salt, carbonate of barytes is soluble in 2300 parts 
of boiling water, and in 4300 parts of cold water. It is still more soluble in 
water containing carbonic acid, and is highly poisonous. The precipitated car- 
bonate of barytes is employed in the analysis of siliceous minerals, containing 
an alkali, which are not soluble in an acid. The mineral, in the state of an 
impalpable powder, is intimately mixed with 4 or 5 times its weight of this car- 
bonate, and exposed in a platugbm crucible to a white heat, which occasions a 
semi-fusion of the mixture and the decomposition of the silicates ; the mineral 
afterwards dissolving entirely in an acid, with the exception of its silica. 

Sulphate of barytes; BaO, SQ 3 ; 1458, or 119.56 This salt consists, in 100 

parts, of 34.37 sulphuric acid and 65.63 barytes. The density of heavy spar, 
or the native sulphate, varies from 4 to 4.47. It occurs in considerable quanti- 
ties, in trap and other igneous rocks, forming often veins of several feet in thick- 
ness, and miles in extent. It is mined for the purpose of being substituted for 
carbonate of lead, or being mixed with that substance, when used as a pigment. 
When chloride of barium is added to sulphuric acid, or to a soluble sulphate, at 
the boiling temperature, sulphate of barytes precipitates readily, in a dense 
crystalline powder, which may easily be washed and collected on a filter. It is 
completely insoluble in water and dilute acids ; but is soluble in concentrated 
and boiling sulphuric acid, from which it crystallizes on cooling. Precipitated 
sulphate of barytes is partially decomposed in a concentrated and boiling solution 
of carbonate of potash or soda, and carbonate of barytes formed. 

Nitrate of barytes; BaO, NO s ; 1633.9, or 130.93.— This salt crystallizes in 
fine transparent octohedrons, which are anhydrous. It is obtained by dissolving 
carbonate of barytes in nitric acid, diluted with 8 or 10 times its weight of water, 
or by mixing the acid, also in a diluted state, with the solution of sulphuret of 
barium. It requires 12 parts of water at 60°, and 3 or 4 of boiling water for 
solution ; it is insoluble in alcohol. The nitrate of barytes is employed as a re- 
agent, and also in procuring pure barytes. 

The chlorate and hyposulphate of barytes are soluble, the iodate, sulphite, 
hyposulphite and phosphates of barytes, insoluble salts. 



SECTION V. 

STRONTIUM. 

Eq. 547.3, or 43.85; Sr. 

Strontium is prepared in the same way as barium, which it greatly resembles. 
It is a white metal, denser than oil of vitriol. It derives its name from Strontian, 
a mining village in Argyleshire. 

Strontian, Strontia, or Strontites; SrO; 647.3, or 51.85. — The native Carbo- 
nate of strontian was first distinguished from carbonate of barytes by Dr. Craw- 
ford, in 1790, who conceived the idea that the former mineral might contain a new 



STRONTIA. 345 

earth. This conjecture was verified in 1793, by Dr. Hope;* and much about 
the same time also by Klaproth. The earth, strontian, is to barytes what soda 
is to potash. It occurs in nature as carbonate and sulphate, but not abundantly. 
Strontian may be prepared by a strong calcination of the native carbonate in 
contact with carbon. It is lighter than barytes, and has a taste which is less 
acrid and caustic, but stronger than that oflime. It is said not to be poisonous. 
The hydrate crystallizes with 9HO, but retains only one equivalent at 212° (Mr. 
Smith.) This last hydrate enters into fusion at a very high temperature, without 
losing its combined water. The pure earth, like barytes, is infusible. The 
crystallized hydrate requires 52 parts of water to dissolve it at 60°, but only 
twice its weight at 212°. 

The soluble salts of strontian are prepared from the carbonate. They are 
precipitated by sulphuric acid and by soluble sulphates, but not so completely 
as the salts of barytes, the sulphate of strontian having a small degree of solu- 
bility. Hence, when sulphate of soda is added in excess to a salt of strontian, 
and the precipitate separated by filtration, so much sulphate of strontian remains 
in solution, that the liquid yields a white precipitate with carbonate of soda (Dr. 
Turner.) Most of the salts of strontian, when heated on platinum wire before 
the blow-pipe, communicate a red colour to the flame. Barytes and strontian 
in solution, may be separated by hydrofluosilicic acid, which precipitates barytes. 
but forms with strontian a salt very soluble in a slight excess of acid. Hypo- 
sulphite of strontian being soluble, while hyposulphite of barytes is insoluble.. 
these earths may also be separated by means of hyposulphite of soda. 

Peroxide of strontium, obtained by Thenard in brilliant crystalline scales, 
on adding peroxide of hydrogen to a solution of strontian. It contains two eq. 
of oxygen. 

Chloride of strontium crystallizes in slender prisms, which contain 9HO, and 
are slightly deliquescent. This salt is soluble in three-fourths of its weight of 
cold water, and in all proportions in boiling water. At the ordinary temperature- 
it dissolves in 24 parts of anhydrous alcohol, and in 19 parts of boiling alcohol. 
In this respect, it differs from chloride of barium, which is insoluble in alcohol. 
Chloride of strontium communicates to flame a fine red tint. In the anhydrous 
condition, this chloride absorbs 4 eq. of ammonia, and becomes a white bulky 
powder. 

Carbonate of strontian forms the mineral strontian iff, which generally has 
a fibrous texture, and is sometimes transparent and colourless, but generally 
has a tinge of yellow or green. Its density varies from 3.4 to 3.726. This salt 
is said to be soluble in 1536 parts of boiling water. It is more soluble in water 
containing carbonic acid, and occurs in some mineral waters. It retains its 
carbonic acid when calcined. 

Sulphate of strontian is known as celestine, and occurs in regular crystals 
of the same form as sulphate of barytes. Its density is about 3.89. It is not 
sensibly soluble in cold water, but is said to be soluble in 3840 times its weight 
of boiling water. This mineral is found in considerable quantity associated with 
volcanic sulphur, and in other formations. The various compounds of strontium 
may be prepared from it, precisely in the same manner as those of barium from 
the sulphate of barytes. 

Hyposulphite of strontian is crystallizable, and soluble in 4 parts of cold, 
and 1| parts of boiling water. It loses 31 per cent, of water of crystallization 
between 122° and 140°, without any other change. 

Nitrate of strontian generally crystallizes in octohedrons, which are anhy- 
drous, but it may be obtained at a low temperature in crystals of another form, 
which contain 5HO. The anhydrous salts dissolves in 5 parts of cold water, and 

* Edinburgh Transactions, iv. 14. 



346 



CALCIUM. 



in I part of boiling water. A deflagrating mixture, which produces an intensely- 
red illumination, is formed of 40 parts of nitrate of strontian, 13 parts of flowers 
of sulphur, 5 parts of chlorate of potash, and 4 parts of sulphuret of antimony. 

The salts of barytes, strontian and lead are strictly isomorphous, and greatly 
resemble each other in solubility and other properties. 



SECTION VI. 

CALCIUM. 

Eq.256, or 20.52; Ca. 

Davy obtained evidence of the existence of this metal, and of its analogy to 
the preceding metals. It is the basis of lime. The name applied to it is derived 
from calx. 

Lime ; CaO ; 356, or 28.52. — Uncombined lime, or quicklime, as it is termed 
in the arts, is obtained by heating masses of lime-stone (carbonate of lime) to 
redness in a lime-kiln, or open fire. The escape of the carbonic acid is favoured 
by the presence of the aqueous vapour and gases of the fire, into which that 
gas can diffuse (page 150.) In a covered crucible carbonate of lime maybe 
fused by heat without decomposition. The lime remains in porous masses r 
which may easily be separated from the ashes of the fuel, and are sufficiently 
hard to be transported from place to place without falling to pieces. Although 
these masses appear light, the density of lime is not less than 2.3, or even 3.08, 
according to Roget and Dumas. Water thrown upon them, is first imbibed, 
and afterwards combines with the lime, which falls to powder in the state of hy- 
drate, and is then said to be slaked. In this combination, the temperature rises 
sufficiently high to char and kindle wood ; but the hydrate is. decomposed, and 
lime is made anhydrous by a red heat. From its affinity for water, quicklime 
is applied to deprive certain liquids, such as alcohol, of the water they contain. 
It is obtained in a suitable state of division for that purpose, by submitting to 
calcination in a crucible the hydrate of lime itself, or by calcining 2 parts of 
hydrate mixed with 3 of pulverulent chalk. For pure lime, the crystallized 
carbonate should be calcined, such as calcareous spar, or Carrara marble. Lime, 
in common with other infusible earths, phosphoresces strongly when heated to 
full redness. 

The hydrate of lime contains 1 eq. of water, which it loses at a low red heat. 
It is sparingly soluble in water, but more soluble in cold than in hot water. Ac- 
cording to Dalton, lime-water formed at 60°, 130° and 212°, contains 1 grain 
of lime in 778, 972 and 1270 grains of water. Hence, water saturated in the 
cold, deposites hydrate of lime, when boiled. By evaporating the solution in 
vacuo, Gay-Lussac obtained hydrate of lime in small transparent crystals of the 
hexahedral form. The milk or cream of lime is merely the hydrate diffused 
through water. Lime-water has a harsh acrid taste, is alkaline, and to a cer- 
tain extent caustic. It precipitates carbonic, silicic, boracic and phosphoric acids 
from solutions of their alkaline salts. It dissolves oxide of lead. Lime-water 
absorbs carbonic acid rapidly from the air, and becomes covered by a pellicle 
of carbonate of lime. Hydrate of lime has the same property, absorbing about 
half an equivalent of carbonic acid with avidity, but not acquiring quite so much 
as three-fourths of an equivalent by 2 or 3 weeks' exposure to an atmosphere of 
the gas. Fuchs observes that when hydrate of lime is exposed to air, it ab- 
sorbs only half an equivalent of carbonic acid, and a definite compound of hy- 
drate and carbonate is formed. In the anhydrous condition, lime exhibits no 
affinity for carbonic acid. 



LIME. 347 

Lime is characterized by affording a bulky precipitate of sulphate of lime, 
when sulphuric acid is added to its soluble salts. But as the sulphate of lime 
has a certain degree of solubility, this precipitate does not appear in very dilute 
solutions of these salts, nor in lime-water, a property by which lime may be 
distinguished from barytes and strontian. Sulphate of lime may also, when 
separated, be re-dissolved by the addition of nitric acid. Lime is entire- 
ty precipitated from neutral solutions, by oxalate of ammonia, the oxa- 
late of lime being completely insoluble. In the quantitative estimation of 
this earth, it is therefore generally thrown down as oxalate, and afterwards 
obtained as carbonate of lime, by heating the oxalate nearly to redness in a pla- 
tinum crucible, in which a small fragment of carbonate of ammonia is dissipated 
at the same time, to prevent any lime becoming caustic by loss of carbonic 
acid. 

Lime is applied to a variety of useful purposes in ordinary life and in the 
arts, of which the most important are its applications as mortar and as a ma- 
nure for land. In the last, lime does not act as an aliment of plants, but is 
useful in accelerating the decomposition of the insoluble organic matter which 
soil contains, and thereby rendering it capable of sustaining vegetable life. 
Hence, the extraordinary fertility which lime developes in soils containing 
peaty matter. In the formation of mortar, the hydrate of lime is mixed with 
2 parts of coarse, or 3 parts of fine sand, and made into a paste with water. 
In building, a stone is laid upon a bed of this paste, which it compresses by 
its weight, imbibing moisture also from the mortar, which escapes principally 
through the porous stone. On drying, the mortar binds the stones between 
which it is interposed, and its own particles cohere so as to form a hard mass, 
solely by the attraction of aggregation, for no chemical combination takes 
place between the lime and sand, and the stones are simply united as two 
pieces of wood are by glue. The sand is useful in rendering insignificant by 
its mass the contraction of the mortar on drying, and also, from the large size 
of its grains, in rendering the dry mortar less short and friable. The mortar 
is subject to an ulterior change, from the slow absorption of carbonic acid, 
but even in the oldest mortar, the conversion of the hydrate of lime into car- 
bonate is never complete. 

Some limestones, containing about 20 per cent, of clay or silicate of alumina, 
afford lime which possesses a valuable property, that of forming with water a 
mass which becomes solid in a few minutes, and therefore hardens in struc- 
tures covered by water. An excellent hydraulic mortar of this kind is ob- 
tained from concretionary masses found in marie, and also as isolated blocks 
in the bed of the Thames. This lime being burnt, ground and sifted, when 
mixed with water to form a paste, sets as quickly as Paris plaster; its solidity 
increases with the time it has been submerged, and it ends by acquiring the 
hardness of limestone. Sand is added to it when it is used as common mor- 
tar, or in covering buildings to imitate stone. From the minute division of 
the silica and alumina in this mortar, their combination with lime is more 
likely to occur than in ordinary mortar. Still the first setting of hydraulic 
mortar seems to be due simply to the fixation of water, and formation of a 
solid hydrate like gypsum. Hydraulic mortar is sometimes made by mixing 
together clay and chalk, and calcining the mixture, or more frequently by 
adding to hydrate of lime puzzolano ground to fine powder. The latter is a 
substance of volcanic origin, composed principally of pumice, of which a 
stratum is excavated in the neighbourhood of Pozzuoli near Naples. The 
mortar which it makes with lime has obtained the name of Roman cement. 

The hydrate of peroxide of calcium precipitates on adding limewater, drop 
by drop, to a solution of peroxide of hydrogen. It contains, according to 
Thenard, 2 eq. of oxygen. 



348 CALCIUM. 

The proto sulphur et of calcium is procured by decomposing sulphate of 
lime at a red heat, by hydrogen or charcoal. When newly prepared, it phos- 
phoresces in the dark. It is sparingly soluble in water. When hydrate of 
lime is boiled with sulphur and water, and the liquor allowed to cool before 
it is completely saturated with sulphur, yellow crystals separate from it, 
which are a bisulphuret of calcium, combined with 3HO, according to the ob- 
servations of Herschel. When lime, or protosulphuret of calcium is boiled 
with excess of sulphur, it dissolves sulphur till a pentasulphurct of calcium is 
formed, which resembles in properties the corresponding degree of sulphura- 
tion of potassium. 

Pfiosphuret of calcium. — Small fragments of quicklime being heated to 
redness, by a spirit lamp, in a small mattrass with a long neck, and fragments 
of phosphorus dropped into the same vessel, a mixture is obtained of phos- 
phate of lime and phosphuret of calcium. The compound has a chocolate 
brown colour. When the temperature is raised too high, the affinities change, 
and phosphorus escaping in vapour, nothing but lime remains. This sub- 
stance decomposes water, when thrown into it, with effervescence, from the 
escape of phosphuretted hydrogen, which takes fire spontaneously, while hy- 
pophosphite of lime is dissolved by the water. 

Chloride of calcium; CaCl; 698.7, or 55.98. — Obtained by neutralizing 
hydrochloric acid with carbonate of lime, or as a residue in several processes; 
a concentrated solution affords crystals in large striated four-sided prisms, 
which contain 6 eq. of water. Dried with stirring, at 300°, it affords a crys- 
talline powder, containing 2 eq. water, which produces an intense degree of 
cold when mixed with snow (page 53.) The crystals are very soluble and 
exceedingly deliquescent. The salt is made anhydrous by heat, and under- 
goes the igneous fusion at a red heat. The liquid chloride is poured upon a 
slab, and the transparent cake of solid salt immediately broken into pieces, 
and preserved in a stopped bottle. It is much employed, from its great affi- 
nity for water, to dry gases and absorb moisture. Chloride of calcium always 
acquires by fusion a slight but sensible alkaline re-action, from partial decom- 
position; on which account Liebig prefers the salt strongly dried, but not 
fused, as the hygrometric agent in organic analysis. Ten parts of anhydrous 
alcohol dissolve 7 of chloride of calcium, at the boiling point, and the solution, 
in cold weather, affords crystals in rectangular scales, which are an alcoate, 
containing about 60 per cent, of alcohol, instead of water of crystallization. 
Anhydrous chloride of calcium likewise absorbs 4 equivalents of ammonia- 
cal gas. 

A solution of chloride of calcium when boiled with hydrate of lime dissolves 
that substance, and the solution filtered hot, deposites long flat and thin crys- 
tals, which contain 49 per cent, of water. The empirical formula of this salt 
is CaCi-f 3CaO-{-15HO. The salt is decomposed by water and alcohol. 

A compound of chloride of calcium with oxalate of lime, containing water 
of crystallization is obtained in good crystals, which are persistent in air, by 
dissolving oxalate of lime to saturation in hot hydrochloric acid and allowing 
the solution to cool. It consists of 1 eq. of each salt, with 7 eq. of water. 
Oxalate of lime is known to combine with 2 eq. of water, of which 1 eq. ap- 
pears to remain in this double salt, while the other is replaced by chloride of 
calcium carrying its 6 atoms of water of crystallization along with it. A simi- 
lar replacement is observed in the formation of quadroxalate of potash (page 
140.) This salt becomes anhydrous without decomposition at 266° (130° 
cent.) It is decomposed by pure water. 

Fluoride of calcium, fluor spar; CaF; 489.8 or 39.25.— This salt occurs 
in nature, massive and in transparent crystals, which are cubes or octohedrons. 
It is often of beautiful colours, generally green or purple, and is cut into orna- 



SALTS OF LIME. 34& 

ments. When heated gently on a plate of metal, it becomes very luminous 
in the dark, or phosphoresces. Fluoride of calcium is insoluble in water, 
and is obtained in a granular condition, when hydrofluoric acid is neutralized 
by freshly precipitated carbonate of lime. But when a neutral salt of lime is 
mixed with a soluble fluoride, the fluoride of calcium appears as a translucent 
gelatinous mass. This fluoride, whether artificial or natural, is not decom- 
posed by sulphuric acid at a low temperature, but imbibes that acid, and forms 
a thick ropy liquid. At 104° (40° cent.) this mixture begins to decompose 
and emits hydrofluoric acid. 



SALTS OF LIME. 

Carbonate of lime; CaC0 2 ; 632.5 or 50.68.— This is one of the most 
abundantly diffused salts in nature, forming the basis of limestones, marbles, 
marles, coral-reefs, shells, &c. It is always anhydrous, and occurs in two 
incompatible crystalline forms, the rhomboidal crystal of calc-spar, which with 
its numerous modifications is much the most abundant, and the six-sided prism 
of arragonite, isomorphous with carbonate of strontian, which may be readily 
recognised by falling to powder when heated. The grains of this powder 
have the form of calc-spar. The density of carbonate of lime in these two 
forms is sensibly different, that of calc-spar being 2.719, and of arragonite 
2.949 (G. Rose.) Carbonate of lime consists in 100 parts, of 56.29 lime and 
43.71 carbonic acid. 

Carbonate of lime may also be obtained in the state of a hydrate, by heat- 
ing together 1 part of hydrate of lime, 3 of sugar, and 6 of water, filtering the 
solution and leaving it to cool in a shallow vessel. In twenty-four hours crys- 
tals appear upon the surface of the liquid, and in fifteen days the whole lime 
is generally converted into hydrated carbonate, in the form of sharp transpa- 
rent rhombs. The carbonic acid is aftorbed from the atmosphere. These 
crystals contain 5 eq. of water. By boiling them in anhydrous alcohol, a 
second definite hydrate is obtained containing 3 eq. of water, as ascertained 
by Pelouze. These correspond in composition with two crystalline hydrates 
of carbonate of magnesia. 

Carbonate of lime is considered an insoluble salt, although according to 
Bucholz it dissolves in 16 or 24 thousand times its weight of pure water. 
But it is soluble in water containing carbonic acid, and is generally present in 
the water of wells, and in some mineral waters to a considerable extent. It 
is deposited from the latter, when exposed to air, in a gradual manner and in 
possession of a crystalline structure, forming stalactites in mountain caverns, 
and calcarious petrifactions, when it flows over wood and other organic and 
destructible matters, of which it preserves the form. It is decomposed with 
effervescence by acids. At a red heat it parts with carbonic acid and is con- 
verted into quicklime in the manner already described. 

A crystalline mineral was discovered by Boussingault at Merida in Ame- 
rica, which he ascertained to be a double carbonate of soda and lime, with 5 
eq. of water, and named Gay-lusnte, in honour of Gay-Lussac. It may be 
made anhydrous by heat, and its two salts are then separated by water. 

Sulphate of lime, gypsum; CaOS0 3 -f-2HO; 857.2+225, or 68.69-f 18.— 
This salt precipitates as a bulky and gritty powder, when sulphuric acid is 
added to a soluble salt of lime. Sulphate of lime appears to have nearly the 
same degree of solubility at all temperatures, and requires 461 parts of water 
for solution. It occurs in nature in well-formed crystals, and also in large 
crystalline masses, forming beds of gypsum; a mineral which contains 2 eq. 
of water, and of which the density is 2.322 (Roget and Dumas.) Mr. John- 
30 



350 CALCIUM. 

ston has likewise obtained small prismatic crystals of sulphate of lime, depo- 
sited in a steam boiler, which contain only half an equivalent of water (page 
240.) Sulphate of lime occurs in a crystalline form, without water, forming 
the mineral anhydrite, of which the density is about 2.96. Sulphate of lime 
fuses at a strong red heat, without decomposition, and on cooling assumes the 
crystalline form of the last mineral. To form plaster of Paris, gypsum, in 
pieces about the size of a pigeon's egg, is heated in an oven till it is nearly 
anhydrous, and then reduced to powder. When this is made into a paste 
with a little water, it forms a hard coherent mass, or sets, in a minute or two, 
with a slight evolution of heat. This artificial hydrate, or stucco, has the 
same composition as native gypsum. If sulphate of lime has been heated 
above 300°, in drying, it refuses to set when mixed with water. 

Hyposulphite of lime is formed by adding sulphurous acid to a solution of 
sulphuret of calcium, till the solution is neutral and colourless. The solution 
is decomposed when heated above 140° (60° cent.) into sulphur and sulphite 
of lime. If evaporated below that temperature, it yields large hexagonal 
prisms of hyposulphite of lime, on cooling, which are colourless. They 
contain 5 eq. of water, and are persistent in air. 

Nitrate of lime is a highly deliquescent, salt, which crystallizes with 6 eq. 
of water, like the nitrates of the magnesian class. It is soluble in alcohol. 

Phosphates of lime. — When earth of bones is dissolved in hydrochloric 
acid, and the solution afterwards neutralized by ammonia, that substance is 
thrown down as a light gelatinous precipitate, which Berzelius has distin- 
guished as the bone-earth phosphate. It contains 8 eq. of lime, with 3 eq. of 
phosphoric acid. When moderately dried, it retains, I find, 4 eq. of water; 
and as it is a tribasic phosphate, its formula probably is 2(3CaO,P0 5 )-fHO, 
2CaO,P0 5 -f3HO. 

On adding chloride of calcium to the tribasic subphosphate of soda, a cor- 
responding phosphate of lime precipitates, of which the formula is 3CaO,P0 5 . 
This phosphate occurs in nature in dlmbination with fluoride of calcium in 
the form of hexagonal prisms, in the minerals apatite and moroxite. The 
formula of apatite is CaF-f-3 (3CaO,PQ^.) The native phosphates of lead 
occur in the same form, with chloride of lead in the place of fluoride of cal- 
cium. Hedyphan is the same mineral, in which a portion of phosphoric 
acid is replaced by arsenic acid. 

Another tribasic phosphate of lime is obtained on pouring the solution of 
common phosphate of soda, drop by drop, into chloride of calcium; the liquid 
becomes acid. This precipitate is slightly crystalline. Its formula, exclusive 
of its water of crystallization, is HO,2CaO,P0 5 . Berzelius describes also a 
biphosphate of lime, obtained on evaporating a solution of the preceding salt 
in nitric acid to the point of crystallization, of which the probable formula is 
2HG,OaO,PQ 5 . There also exist a pyrophosphate and metaphosphate of 
lime. Theinsoluble phosphates of lime are soluble in water containing car- 
bonic acid. It is possibly in this manner that phosphate of lime is dissolved 
by the alkaline animal fluids. 

Chloride of lime, bleaching powder. — This compound is equally remarka- 
ble for its valuable applications in the arts, and for the discussions to which 
its anomalous or doubtful constitution has given rise. It is generally pre- 
pared by exposing hydrate of lime, from the purest lime, to chlorine gas, the 
latter being supplied so gradually as to prevent the heat, occasioned by the 
combination, from rising above 62°. When dried at 212,° hydrate of lime, I 
find, absorbs afterwards little or no chlorine; but dried over sulphuric acid, 
without heat, it is, on the contrary, in the most favourable condition for 
making chloride of lime. A dry, white, purverulent compound is obtained, 
by exposing the last hydrate to chlorine, which contains, 41.2 or 41.4 chlorine,. 



CHLORIDE OF LIME. 351 

in 100 parts; but of this chlorine about 39 parts only are available for bleach- 
ing", owing- to 2 parts of that element going to the formation of chloride of cal- 
cium and chlorate of lime. A slight addition of moisture to hydrate of lime 
does not increase the proportion of chlorine absorbed, and renders the com- 
pound less stable. The above appears to be the maximum absorption of 
chlorine by dry hydrate of lime, and is greater than it would be advisable to 
attempt in the manufacture of bleaching powder, owing to the occurrence of 
the partial decomposition adverted to. Yet this proportion is considerably 
short of 1 eq. of chlorine to 1 of hydrate of lime, which are 48.57 chlorine 
and 51.43 hydrate of lime, in 100 parts. The excess of lime appears to be 
useful in adding to the stability of the compound. The bleaching powder of 
commerce may contain, when newly prepared, about 30 per cent, of chlorine. 
As I have found it in the shops of the apothecaries, the proportion of availa- 
ble chlorine was more frequently below than above 10 per cent., so much 
does it deteriorate by keeping. 

The same compound is obtained in solution by transmitting a stream of chlo- 
rine gas through hydrate of lime suspended in water. The lime then absorbs 
a full equivalent of chlorine, and dissolves entirely. Ten parts of water take 
up the bleaching combination from one part of dry chloride of lime, leaving 
undissolved the hydrate of lime contained in excess. The solution has a strong 
alkaline reaction. It destroys most organic matters containing hydrogen, in- 
cluding colouring matters. But its bleaching action is not instantaneous, un- 
less an acid be added to it, which liberates the chlorine. Hence when Turkey- 
red cloth, having a pattern printed upon it with tartaric acid thickened by gum. 
is immersed for about one minute in this solution, it comes out with the colour 
discharged where the acid was present, but elsewhere uninjured. In this man- 
ner white figures are produced upon a coloured ground. The solution of chlo- 
ride of lime also absorbs and destroys contagious matters in the atmosphere, 
and is slowly decomposed by carbonic acid, with escape of chlorine. The 
powder or its solution, when heated, or when kept for a considerable time, un- 
dergoes decomposition; 18 eq. of chlorine, then leaving 17 eq. of chloride of 
calcium, and 1 eq. of chlorate of lime, and disengaging 12 eq. of oxygen gas, 
according to the observations of M. Morin. 



CONSTITUTION OF CHLORIDE OF LIME. 

Chloride of lime for bleaching was first prepared by the late Mr. Tennant 
of Glasgow, who in conjunction with some scientific friends, obtained a patent 
for the manufacture of the dry compound in 1799. For some time after the 
true nature of chlorine was known, bleaching powder appears to have been 
looked upon as simply a combination of chlorine with lime. But more accu- 
rate views of combination lead Berzelius to question the possibility of com- 
pounds of elementary bodies with binary compounds, which, if they exist, are 
certainly exceedingly rare, and to observe the similarity in the absorption of 
chlorine by lime, with its absorption by a strong solution of potash and the 
formation of chloric acid, and with the solution of sulphur in alkalies and 
formation of hyposulphurous acid. He concluded that a chlorous acid existed 
in the bleaching compounds of chlorine, consisting of 1 eq. of chlorine and 3 
of oxygen; the oxygen of this acid being derived from the metallic oxide like 
that of chloric and hyposulphurous acids, a corresponding quantity of metallic 
chloride being produced at the same time. This opinion was generally re- 
ceived, the bleaching power of the compound being referred to the facility 
with which chlorite of lime parts with 4 eq. of oxygen, and becomes chloride 



352 CALCIUM, 

of calcium. The subsequent discovery by M. Balard, of hypochlorous acid, a 
bleaching compound of chlorine and oxygen, which can be isolated, lent sup- 
port to the same view, although it altered the expression of it, hypochlorous 
acid being substituted in these compounds for the chlorous, of the separate ex- 
istence of which there is no evidence. Hypochlorous acid is actually absorbed 
by hydrate of lime and by solutions of alkalies, with the formation of bleach- 
ing compounds, but the identity of these with the compounds resulting from 
the absorption of chlorine itself is doubtful. The hypochlorous compounds 
are much less stable than the old chlorides, according to the observations of M. 
Martens*. 

M. E. Millon has quite recently announced some curious discoveries re- 
specting these compounds, which lead him to take a new and simpler view of 
their constitution. When the solution of chloride of lime is added to nitrate 
of lead, a white precipitate falls, which after a time becomes brown. In the 
first state it has hitherto been taken for chloride, and in the second for peroxide 
of lead, but Millon finds that it is a compound of protoxide of lead with chlo- 
rine, in both conditions, or Pb-fO,Cl. With protonitrate of iron, a brown 
precipitate, of similar constitution, Fe 2 +0 2 ,C1 is produced; and white proto- 
salts of manganese a similar precipitate, but containing twice as much chlorine. 
In the case of each of these three nitrates, the new compound corresponds with 
the peroxide of the same metal, the protoxide acquiring chlorine instead of 
oxygen. The red oxide, or suboxide of copper also, when warmed, absorbs 
half an equivalent of chlorine; becoming 2Cu-f-0,Cl, which corresponds'with 
the black oxide, the highest degree of oxidation of that metal. Potash, he 
finds also, to absorb 2 equivalents of chlorine, forming a compound K-{-0,2Cl, 
corresponding with the peroxide of potassium., K0 3 ; while soda absorbs only 
1 eq. of chlorine, forming Na-}-0,Cl; the peroxide of sodium containing less 
oxygen than the peroxide of potassium, although the composition of the former 
appears not to be certainly determined. M. Millon concludes that the compounds 
formed when chlorine is absorbed by metallic protoxides are bodies analogous 
to the peroxides of the same metals, but in which the place of a portion of the 
oxygen is held by chlorine. Bleaching powder is thus a compound of calcium 
with oxygen and chlorine, in a hydrated condition, analogous to hydrated per- 
oxide of calcium, or hydrated peroxide of barium which is better known. As 
a peroxide of hydrogen exists, the possibility is inferred of an analogous com- 
pound of hydrogen with oxygen and chlorine, H-}-0,Cl, which may be con- 
tained in the crystalline compound hitherto viewed as a hydrate of chlorinef. 
We have already admitted similar substitutions of chlorine for oxygen, as in 
chlorosulphuric acid (page 242.) The relation between a hydrated peroxide, 
such as that of barium, and chloride of lime appears, in both being decom- 
posed by acids, which unite with the barytes and lime, and liberate oxygen 
from the one compound and chlorine from the other. Peroxide of hydrogen also 
rivals the chlorine compounds, in bleaching power. But when the replacing 
bodies differ so much from each other as chlorine and oxygen, it is not to be 
expected that the resulting compounds will exhibit the closest analogy in pro- 
perties. 



CHLORIMETRY. 

The bleaching power of chloride of lime is often estimated by the quantity 
of a solution of sulphate of indigo, which a known weight of chloride can 

* An. de Ch. et de Ph. t. 61, p. 293. 

t Journal de Pharmacie, Sept. 1839, page 595. 



CHLORIMETRY. 353 

discolour or render yellow. But as the indigo solution alters by keeping-, this 
method is not unobjectionable. Several exact methods have been proposed, of 
which that in which sulphate of iron is used appears to be entitled to prefe- 
rence. This method reposes upon the circumstance that the chlorine of chlo- 
ride of lime converts a salt of the protoxide into a salt of the peroxide of iron; 
half an equivalent, or 221.3 parts of chlorine, effecting that change upon a 
whole equivalent, or 17.28 parts of cr. protosulphate of iron. Protoxide of 
iron is convertible into peroxide by half an equivalent of oxygen, which the 
half equivalent of chlorine may be supposed to supply, by decomposing water, 
in becoming hydrochloric acid. It follows, by proportion, that 10 grains of 
chlorine are capable of peroxidizing 78.1 grains of cr. sulphate of iron. 

A few ounces of good crystals of protosulphate of iron are reduced to 
powder, and dried by strong pressure between folds of cloth; the salt may af- 
terwards be preserved in a bottle without change. In a chlorimetric experi- 
ment 78 grains (equivalent to 10 grains of chlorine) of this salt are dissolved 
in about two ounces of water, which may be acidulated by a few drops of sul- 
phuric or hydrochloric acid. Fifty grains of the chloride of lime to be ex- 
amined are dissolved in about two ounces of tepid water, by rubbing them to- 
gether in a mortar, and the whole poured into the alkalimeter (page 329;) 
which is afterwards filled up to on the scale, by. the addition of water, and 
the whole mixed by inverting the alkalimeter upon the palm of the hand. The 
solution of chloride of lime, being thus»made up to 100 measures, is .poured 
gradually into the sulphate of iron, till the latter is completely peroxidized, 
and the number of measures of chloride required to produce that effect ob- 
served. The change in the degree of oxidation of the iron solution is disco- 
vered by means of red prussiate of potash, which gives a precipitate of prus- 
sian blue with a salt of the protoxide of iron only, and not with a salt of the 
peroxide. By means of a glass stirrer, a white stoneware plate is spotted 
over with small drops of the prussiate. A drop of the iron solution is mixed 
with one of these, after every addition of chloride of lime, and the additions 
continued, so long as a deep blue precipitate, is produced. The liquid may 
continue to be coloured green by the iron salt, but that is of no moment. The 
richer the specimen of chloride of lime is in chlorine, the fewer measures of 
its solution are required to peroxidize the iron, the number of measures con- 
taining 10 grains of chlorine always producing that effect. The quantity of 
chlorine in the fifty grains of bleaching powder is upw known, being ascer- 
tained by the proportion, as m measures the number poured out of the alkali- 
meter is to 10 grains of chlorine, so 100 is to the total grains of chlorine. In 
a particular experiment the 78 grains of sulphate of iron required 72 measures 
of the bleaching solution. Hence, as 72 is to 10, so 100 is to 13.89 chlorine 
in 50 grains of the chloride of lime. The quantity of chlorine in 100 grains 
of the chloride, or the per centage of chlorine, is obtained by doubling that 
number, and was therefore in this instance 27.78 per cent, or 28 per cent. 
The arithmetical process may always be reduced to that of dividing 2000' 
by the number of measures poured from the alkalimeter; thus in the last 
example — 

*292 -27.78. 
72 



30* 



354 MAGNESIUM. 

SECTION VII. 

MAGNESIUM. 
Eq. 158.3, or 12.69; Mg. 

To obtain magnesium, sodium in a test-tube of hard glass is covered by 
fragments of anhydrous chloride of magnesium, and heated to redness by a lamp. 
The alkaline metal unites with chlorine, with strong ignition. After extracting 
the chloride of sodium by means of water, the magnesium remains in little 
globules, which may be re-united, by fusing them under a stratum of chloride 
of potassium at a moderate red heat. 

Magnesium has the colour and lustre of silver ; it is malleable, and fuses at a 
red heat. It is oxidized superficially by moist air, but undergoes no change in 
dry air or oxygen. Heated to redness, it burns with great brilliancy, forming 
magnesia. It is evidently more analogous to zinc than to the preceding metals. 

Magnesia; MgO ; 258.3, or 20.69. — This is the only known oxide of mag- 
nesium. As usually prepared by calcining the artificial carbonate of magnesia, 
it forms the magnesia usta of pharmacy. Magnesia is a white soft powder, of 
density about 2.3, and highly infusible. It combines with water, but with much 
less avidity than lime, forming a protohydrate. The native hydrate of magnesia 
has the same composition, and so has the compound, obtained by precipitating 
magnesia from its soluble salts, when dried, either without heat, or at 212°. 
These preparations have a silky lustre and a softness to the touch, characteristic 
of magnesian minerals, such as is observed in asbestos and soapstone. Ac- 
cording to Dr. Fyfe, magnesia requires, for solution, 5142 times its weight of 
water at 60°, and 36,000 times its weight of boiling water. This earth, when 
mixed with a blue infusion of cabbage, causes it to become green, and is there- 
fore alkaline. 

Chloride of magnesium, made by neutralizing carbonate of magnesia with 
hydrochloric acid, crystallizes with 6HO,is very soluble and highly deliquescent. • 
When we attempt to make it anhydrous by heat, hydrochloric acid escapes, 
and magnesia remains. But the pure chloride, which is employed in preparing' 
the metal, maybe obtained by dividing a quantity of hydrochloric acid into two 
equal portions, neutralizing one with magnesia, and the other with ammonia, 
mixing and evaporating these two solutions to dryness, when an anhydrous 
double chloride of magnesium and ammonia is formed. On heating this salt to 
redness in a porcelain crucible, sal-ammoniac sublimes, and chloride of mag- 
nesium remains in a state of fusion, which becomes a translucent crystalline 
mass on cooling. This chloride is decomposed by oxygen, which, at a high 
temperature, displaces its chlorine, and magnesia is formed. 

Carbonate of magnesia. — This salt occurs native, generally as a white, hard, 
compact mineral of an earthy fracture, which is known as magnesite, and some- 
times in rhombohedral crystals, similar to those of carbonate of lime. It is pre- 
pared artificially by precipitating a soluble salt of magnesia, by means of carbo- 
nate of potash at the boiling point. The precipitate is diffused in pure water, 
and a stream of carbonic acid sent through it, by which the carbonate of mag- 
nesia is dissolved. On allowing this solution to evaporate spontaneously the 
excess of carbonic acid escapes, and carbonate of magnesia is deposited in small 
hexagonal prisms with right summits. These crystals contain 3 eq. of water. 
They effloresce in dry air, and then lose 2 eq. of water, according to my own 
observations. Carbonate of magnesia has also been obtained in crystals with 



SALTS OF MAGNESIA. 355 

5 eq. of water. There are, consequently, three hydrates of this salt, of which 
the formulae are, 

MgO, C0 2 , HO; 

MgO, C0 o ,H0 + 2H0; 

MgO, C0 2 ,HO + 4HO. 
The fact that this salt dissolves in carbonic acid water is not to be held as 
proof of the existence of a bicarbonate of magnesia. Various insoluble salts, 
such as phosphate of lime and fluoride of calcium dissolve in the same liquid, 
which appears to possess a specific solvent power. In the analogous solution 
of carbonate of lime in carbonic acid water, the proportion of the carbonate 
was found by Berthollet to have a variable and indefinite relation to the acid. 
On theoretical grounds, supersalts of magnesia, or the magnesian family of 
oxides, of the ordinary constitution, are not to be expected, as they would be 
double salts of water and another magnesian oxide. 

Magnesia alba, or the subcarbonate of magnesia of pharmacy, is prepared by 
precipitating a boiling solution of sulphate of magnesia or chloride of mag- 
nesium, by means of carbonate of potash. Carbonate of soda is not so suitable 
as a precipitant of magnesia, as a portion of it is apt to go down in combination 
with the magnesian carbonate, but it may be used provided the quantity applied 
be less than is required to decompose the whole magnesian salt in solution. 
Magnesia alba, when well washed with hot water is very white, light and bulky. 
A portion of carbonic acid is lost, the magnesia not being in combination with a 
full equivalent of that acid. Berzelius found magnesia alba to contain, in 100 
parts, 35.77 carbonic acid, 44.75 magnesia, and 19.48 water, or to consist of 3 
eq. of carbonic acid, 4 eq. of magnesia, and 4 eq. of water. He views it as a 
combination of hydrate of magnesia with hydrated carbonate of magnesia, of 
which the formula is MgO, HO + 3(MgO, C0 2 , HO.) This compound is said to 
require 2493 parts of cold, and 9000 of hot water for solution. 

Bicarbonate of potash and magnesia. — This salt was formed by Berzelius 
by mixing a solution of nitrate of magnesia or chloride of magnesium, with a 
saturated solution of bicarbonate of potash in excess, and allowing the liquor to 
rest. In the course of a few days, the double salt is deposited in large regular 
crystals. These crystals are insipid. They are insoluble in pure water, but 
are slowly decomposed by it. The composition of this salt corresponds with 1 
eq. of potash, 2 of magnesia, 4 of carbonic acid, and 9 of water. As a compound 
of 1 eq. of bicarbonate of potash and 2 of carbonate of magnesia, it may be 
represented thus : — 

MgO, C0 2 ,HO-i-2HO 

HO, C0 2 , (KO, C0 2 )+2HO 

MgO,C0 2 ,HO+2HO 

But a compound like this, of three salts of similar constitution, is not easily re- 
conciled with the ordinary laws of saline combination. This salt loses 8HO, at 
212°, or all its combined water, except the single basic equivalent. A corre- 
sponding bicarbonate of soda and magnesia also exists. 

Dolomite, a magnesian limestone, very extensively diffused in nature, is a 
mixture or combination of the carbonates of lime and magnesia, having the 
crystalline form of calc-spar. The two salts are almost always in the proportion 
of single equivalents. It is remarkable that when this rock is exposed to the 
solvent action of water containing carbonic acid, the carbonate of lime is dis- 
solved exclusively, and a magnesian limestone remains in the form of a porous 
and crystalline mass. It is not unusual to find whole mountains of magnesian 
limestone thus altered. 

Sulphate of magnesia; MgO, S0 3 , HO-f 6HO; 759.6+787.5, or 60>86-f 63. 



356 



MAGNESIUM. 




This salt exists in many mineral springs, in the waters of Epsom, of Seidlitz 
in Bohemia, &c., from which it was first procured by evaporation. It is now 
generally obtained from the bittern of seawater, which consists principally of 
chloride of magnesium and sulphate of magnesia, and is converted wholly into 
sulphate by the addition of sulphuric acid. Or magnesia is precipitated from 
seawater confined in a tank, by means of hydrate of lime, and the earth thus 
obtained, afterwards neutralized by sulphuric acid. Magnesian limestone is also 
had recourse to for magnesia. It is burnt and slaked with water, to obtain it 
in a divided state, and then neutralized by sulphuric acid. The mixed sulphates 
are easily separated, that of lime being soluble to a small extent only, while that 
of magnesia is highly soluble in water. A solution of sulphate of lime is also 
decomposed by carbonate of magnesia, with the formation of sulphate of mag- 
nesia, and this reaction is often witnessed in beds of magnesian limestone, when 
water containing sulphate of lime, percolates through them. 

The crystals of sulphate of magnesia are four-sided rectangular prisms, 
which when pure, have a slight disposition to effloresce in dry air. One hun- 
dred parts of water at 32° dissolve 25.76 parts of the an- 
hydrous salt, and for every degree above that temperature, 
they take up 0.26564 part additional, (see Gay-Lussac's 
table of the solubility of salts, at page 147.) The solution 
has a bitter disagreeable taste, which is characteristic of all 
the soluble salts of magnesia. It is not precipitated in the 7 
cold by the alkaline bicarbonates, by common carbonate of 
ammonia, nor by oxalate of ammonia if the solution of sul- 
phate of magnesia be dilute. 

Sulphate of magnesia loses 6HO considerably under 300°, 
but retains 1 eq. even at 400°. The last equivalent is re- 
placed by sulphate of potash, forming the double sulphate of 
magnesia and potash, which is considerably less soluble than 
the sulphate of magnesia, and crystallizes with 6HO. Sulphate of magnesia 
unites directly with sulphate of ammonia also, when solutions of the salts are 
used, but not with sulphate of soda. A double sulphate of magnesia and soda 
occurs, however, in the manufacture of sulphate of magnesia, which is said 
to have 6HO, like the potash salt, but a different form. 

Sulphate of magnesia, when ignited in contact with charcoal, leaves a sul- 
phuret of the metal, but it is the last of the earths which exibits this analogy to 
the alkalies. The sulphuret of magnesium is soluble in water. It may like- 
wise be obtained by precipitating sulphate of magnesia by sulphuret of barium. 
Hypo sulphate of magnesia forms crystals, which are persistent in air, very 
soluble, and contain 36.77 per cent, or 6 atoms of water of crystallization, like 
the following salt. 

Nitrate of magnesia is a very soluble and highly deliquescent salt. It crys- 
tallizes with 6HO, five of which it loses at a high temperature. The remain- 
ing hydrate may be fused without decomposition, but when heated more 
strongly, it loses both nitric acid and water, and pure magnesia is left. It ap- 
pears that one equivalent of water is essential to the existence of this and all 
other nitrates of the magnesian class of oxides. That water is not displaced by 
nitrate of potash heated in contact with the magnesian nitrate. Nitrate of 
magnesia is very soluble in alcohol, and forms a solid alcoate, in which proba- 
bly a portion of water is associated with the alcohol. I did not succeed in 
forming a double nitrate of magnesia and ammonia, (nor any other double ni- 
trate,) although such a salt is admitted by Berzelius. 

Phosphate of magnesia is formed on mixing cold solutions of common 
phosphate of soda and of sulphate of magnesia, and allowing the liquid to stand 
for 24 hours. The salt appears in tufts of slender prisms, which effloresce in 



SALTS OF MAGNESIA. 357 

dry air. They are soluble in about 1000 times their weight of water. The 
composition of this salt, which I carefully examined, may be expressed by the 
following formula, HO, 2MgO, P0 5 +2HO + 12HO. (Phil. Trans. 1837.) 

Phosphate of magnesia and ammonia. — This is the well-known granular 
precipitate, which appears, when a tribasic phosphate and a salt of ammonia 
are dissolved together, and any salt of magnesia is added to the mixture. Its 
formation is had recourse to as a test of the presence of magnesia. Although in- 
soluble in a liquid containing salts, it is so soluble in pure water that it cannot 
be washed without sensible loss. It is readily dissolved by acids. The same 
substance forms the basis of the variety of urinary calculus, known as the am- 
moniaco-magnesian phosphate. It is a tribasic phosphate, of which the 3 atoms 
of base are 1 atom of oxide of ammonium and 2 atoms of magnesia, with 12 
atoms of water of crystallization ; ten of the latter may be expelled without any 
loss of ammonia. The formula of this salt is therefore KH 4 0,2MgO, P0 5 + 
2HO-fl0HO. Dr. Otto has observed a corresponding tribasic phosphate of 
protoxide of iron and ammonia, which contains only two atoms of water of 
crystallization ; and also an arseniate of manganese and ammonia, of which the 
water of crystallization appears to be the same as that of the phosphate of mag- 
nesia and ammonia. 

Borate af magnesia. — The neutral salt was obtained by Wohler, in the 
form of crystals, by heating a mixture of the solutions of sulphate of magnesia 
and borax to the boiling point, to form a precipitate, and allowing the liquid to di- 
gest for some time upon this precipitate, at a temperature only a few degrees 
above 32°. The precipitate re-dissolves, and there are formed on the sides of 
the vessel thin crystalline needles, transparent, brilliant, hard, and having much 
of a mineral character. They are insoluble in hot or cold water. They lose 
by heat 58.4 per cent, of water, or 8 atoms, and leave a compound of single 
equivalents of boracic acid and magnesia, MgO, B0 3 . After the deposition of 
this neutral borate, the liquid affords large crystals of a double borate of soda 
and magnesia, containing 52.5 per cent, of water, but of which the proportions 
of the constitutent salts have not been determined. 

The mineral boracite, which occurs in the cube and its allied forms, is an 
anhydrous compound of magnesia and boracic acid, in the extraordinary ratio 
of 3 eq. of magnesia to 4 of boracic acid, or its formula is 3MgO -f 4BO 3 . This 
mineral becomes electrical by heat. The rare mineral, hydroboracile, is, ac- 
cording to Hess, a compound of a borate of lime and borate of magnesia, in both 
of which the acid and base are in the same ratio as in boracite, with 18 eq. of 
water. 

Silicates of magnesia. — Magnesia is found combined with silicic acid in 
various proportions, forming several mineral species, of which the formulae are 
as follows: — 

Steatite . . . MgO, Si0 3 . 
Meerschaum . . MgO, Si0 3 -f HO. 
Picrosmine and pyrallolite 3MgO + 2Si0 3 . 
Periote (olivine, or chryso- } ,, _ . ~.„ 
lyte) . . . JSMgO+SiO,. 

Serpentine (hydrate ofi 

magnesia with subsili- ^3MgO, 6HO + 2(3MgO + 2Si0 3 .) 

cate of magnesia) . J 
Pyroxene or augite (siliO 

cate of lime and magne- V3CaO, 2Si0 3 +3Mg0, 2Si0 3 . 

sia) .... J 
Amphibole, or hornblende 1 

(silicate of lime and IcaO, Si0 3 -f 3MgO, 2Si0 3 . 

magnesia) , . J 



358 ALUMINUM. 

In these minerals, particularly the two last, the magnesia is often replaced in 
whole or in part by protoxide of iron, which gives them a green, and sometimes 
black colour. Fine crystals of pyroxene are often found among the scoriae of 
blast furnaces. Serpentine is easily decomposed by acids, and may be em- 
ployed in the preparation of sulphate of mao-nesia. 



ORDER III. 

METALLIC BASES OF THE EARTHS. 

SECTION VIII. 
ALUMINUM. 

Eq. 171.2, or 13.72; Al. 

This element is named from alumen, the Latin term for alum, which is as> 
double salt, consisting of sulphate of alumina and sulphate of potash. 

Like the preceding metal, aluminum is obtained from its chloride, by the ac- 
tion of potassium. But the decomposition must be effected in a platinum or 
porcelain crucible, as the heat evolved from the reaction, which occurs, would fuse 
glass. Eight or 10 grains of potassium are covered by a quantity of anhydrous 
chloride of aluminum, containing, as nearly as possible, the proportion of chlo- 
rine equivalent to the potassium ; the lid of the crucible is fastened down by a 
wire, and the heat of a lamp applied. The action which follows is violent, and 
attended with the evolution of much heat. The aluminum is afterwards sepa- 
rated from the chloride of potassium, with which it is mixed, by digesting the 
crucible and its contents in a considerable quantity of cold water. The metal 
appears as a gray powder, resembling spongy platinum, but is seen in a strong 
light, while suspended in water, to consist of small scales or spangles having the 
metallic lustre. It is not a conductor of electricity when in this divided state, 
but becomes one when its particles are approximated by fusion. Wohler finds 
that iron resembles aluminum in that respect. 

Aluminum has no action upon water at the usual temperature, but decomposes 
it to a small extent, at the boiling temperature, with the evolution of hydrogen. It 
undergoes oxidation more rapidly in solutions of potash, soda and ammonia, 
and the resulting alumina is dissolved by these alkalies. Aluminum requires for 
fusion a temperature higher than that at which cast iron melts. Heated in 
open air it takes fire and burns with a vivid light, and in oxygen gas with the 
production of so much heat as to fuse the alumina, which then has a yellow- 
ish colour, and is equal in hardness to the native crystallized aluminous earth, 
corundum. 

Alumina; A1 2 3 ; 642.4, or 51.44. — This earth is the only degree of oxi- 
dation of which aluminum is susceptible, so far as is known at present. In its 
constitution, alumina is presumed to resemble peroxide of iron, because it occurs 
crystallized in the same form as the native peroxide of iron, and the salts, into 
which it enters, are strictly isomorphous with the corresponding salts of that 
oxide. To three atoms of oxygen it must, therefore, contain two atoms of 
metal, such being the composition of the peroxide of iron. Aluminum is not 



ALUMINA. 359 

known to enter into any other combination in a less proportion than two 
equivalents. 

Alumina occurs in a state of purity, with the exception of a trace of colour- 
ing matter, in two precious stones, the sapphire and ruby, the first of which is 
blue and the other red. They are not inferior in hardness to the diamond. 
Their density is from 3.9 to 3.97. It may be obtained by calcining the sulphate 
of alumina and ammonia, or ammoniacal alum, very strongly. But alumina 
so prepared is insoluble in acids. It is obtained in the state of a hydrate from 
common alum, by dissolving the latter in boiling water, and adding a solution 
of carbonate of potash till it no longer causes a precipitate : a slight excess of 
the carbonate may then be added, and the whole allowed to digest at a gentle 
heat for some time, in order to decompose a subsulphate of alumina which 
the alkali first throws down. The precipitate, which is white, gelatinous, and 
very bulky, must be very carefully washed by mixing it several times with a 
large quantity of distilled water, allowing it to settle and pouring off the clear 
liquid, or by affusion and decantation, as it is said. The precipitate is then dis- 
solved in hydrochloric acid, the solution filtered, if not clear, and precipitated again 
by ammonia or its carbonate. This last operation is necessary, in order to get rid 
of a portion of carbonate of potash which remains attached to alumina, when 
precipitated by that salt. Ammonia cannot be substituted for potash in the first 
precipitation, as it throws down a subsulphate of alumina, and does not deprive 
the earth entirely of its acid. The alumina of the second precipitation is also in 
the state of a subsalt, unless ammonia be added in excess, which is capable of 
decomposing completely the subsalt from hydrochloric acid. The alumina must 
again be carefully washed, as before, to get rid of every portion of the liquid in 
which it was precipitated. By drying in air, alumina is reduced to a few 
hundredths of the bulk of the humid mass. It is still a hydrate, but when ig- 
nited at a high temperature, it gives pure alumina. One hundred parts of alum 
furnish only 10.3 parts of alumina. 

Alumina is white and friable. It has no taste, but adheres to the tongue. 
Before the oxihydrogen blow-pipe, it melts into a colourless glass. After being 
ignited, it is dissolved by acids with great difficulty. It is highly 'hygrometric, 
condensing about 15 per cent, of moisture from the atmosphere in damp weather. 
If ignited alumina contains a small portion of magnesia, it becomes warm when 
moistened with water; this property is very sensible, even when the proportion 
of magnesia does not exceed half a per cent. It appears to be due to heat dis- 
engaged by humectation, a phenomenon first observed by Pouillet. 

The hydrate of alumina, when moist, is gelatinous and semi-transparent, like 
starch, but dries up into gummy masses. It is completely insoluble in water, 
but is readily dissolved by acids, and also by the fixed alkalies. Caustic 
ammonia dissolves it, only in very small quantity. When an excess of the hy- 
drate, immediately after precipitation, is digested in caustic potash, by a mode- 
rate temperature, and the solution filtered and sealed up in a flask, there separate 
from it after a time crystals upon the sides of the vessel. The same crystals 
are obtained, on allowing the solution to absorb carbonic acid slowly from the 
air. They are white and transparent at the edges, and contain 34.61 per cent, of 
water, or 3 equivalents which they do not lose at 212°. (Mitscherlich's Traite.) 
The mineral gibbsite is a native hydrate of alumina of the same composition, 
Al 2 3 -f3HO. Another native hydrate exists, containing less water, Al 9 3 -f 
2HO. It is called diaspor by mineralogists, from decrepitating and falling to 
powder when heated, a property which the artificial hydrate in gummy masses 
likewise exhibits. 

Hydrated alumina has a peculiar attraction for organic matter, which it with- 
draws from solution, and hence this earth is apt to be discoloured when washed 
with water not absolutely pure. This affinity is so strong, that when digested 



360 ALUMINUM. 

in solutions of vegetable colouring matters, alumina combines with, and carries 
down the colouring matter, which is removed entirely from the liquid, if the 
alumina is in sufficient quantity. The pigments called lakes are such alumi- 
nous compounds. The fibre of cotton, when charged with this earth, attracts 
and retains with force the same colouring matters. Hence the great application 
of aluminous salts in dyeing, to impregnate cloth or yarn with alumina, and 
thus enable it to fix the colouring matter, and produce a fast colour. 

Alumina, it will be observed, is not a protoxide, and is greatly inferior to the 
preceding earths in basic power. It is dissolved by acids, but never neutralizes 
them completely. Hence, alum and all the salts of alumina have an acid re- 
action. Their solutions have an astringent and sweetish taste which is peculiar 
to them. Alumina dissolves, to the extent of several equivalents, in some acids, 
particularly hydrochloric acid, forming feeble compounds, which are even de- 
prived of a portion of their alumina, by filtering them through paper. It does 
not combine with some of the weaker acids, such as carbonic acid. Hence an 
alkaline carbonate throws down alumina from alum, and not a carbonate of 
that earth. Alumina dissolves readily in solutions of potash or soda, forming 
compounds in which it must play the part of an acid. Such combinations occur 
in nature, spinell being an aluminate of magnesia (MgO,Al 2 3 ,) and gahnite 
an aluminate of zinc (ZnO,Al 2 3 .) 

All the known compounds of aluminum correspond with alumina, in the ratio 
of their equivalents, that is, to two atoms of aluminum they contain three atoms 
of another body. 

Sulphur et of aluminum is formed by burning the metal in the vapour of 
sulphur. It is a black semi-metallic mass, which is rapidly transformed, by con- 
tact of water, into alumina and sulphuretted hydrogen. Hydrosulphuret of 
ammonia has the same effect upon the solution of a salt of alumina, as ammonia 
itself, neutralizing the acid of the salt, and throwing down alumina, while sul- 
phuretted hydrogen escapes. 

Chloride of aluminum ; A1 2 C1 3 ; 1670.3 or 133.84. — When alumina is dis- 
solved in hydrochloric acid, it is to be supposed that water and a chloride of 
the metal are formed (3HC1 and A1 2 3 =A1 2 C1 3 and 3HO.) The solution, 
when concentrated by spontaneous evaporation in a very dry atmosphere, 
yields crystals, which BonsdorrT found to contain 44.7 per cent, or 12 eq. of 
water. But it generally forms a saline mass, which deliquesces quickly in the 
air. When it is attempted to make this salt anhydrous by heat, the chlorine 
goes off in the form of hydrochloric acid, and pure alumina is left. 

The anhydrous chloride was discovered by Oersted, who made known a 
method of preparing it, which has since had numerous applications. Pure alu- 
mina, free from potash, is intimately mixed with carbon, in the form of lamp- 
black, and strongly calcined in a crucible. The alumina is thus made anhydrous, 
without being otherwise altered. It is then introduced into a porcelain tube, 
which is placed across a furnace and exposed to a red heat. Chlorine gas, 
carefully dried, is conducted over the materials in the tube, when, under the 
conjoint influence of carbon and chlorine the alumina is decomposed ; its oxy- 
gen is carried off by the carbon as carbonic oxide gas, and chlorine unites with 
the aluminum itself, in the place of oxygen. The chloride of aluminum, being 
volatile, sublimes and condenses in the cool part of the porcelain tube. A glass 
tube, a little smaller than the porcelain tube, should be introduced into this part 
of the latter, which may afterwards be drawn out, containing the "Condensed 
chloride. The salt is partly in the state of long crystalline needles, and partly 
in the form of a firm and solid mass which is easily detached from the glass. 

Chloride of aluminum is of a pale greenish yellow colour, and to a certain 
degree translucent. In air it fumes slightly, diffuses an odour of hydrochloric 
acid, and runs into a liquid by the absorption of moisture. It is very soluble 



SALTS OF ALUMINA. 361 

in water, but cannot again be recovered in the anhydrous condition. It is 
equally soluble in alcohol. Chloride of aluminum combines with sulphuretted 
hydrogen, phosphuretted hydrogen, and also with ammonia. The latter com- 
pound Persoz finds to contain 27.61 per cent, of ammonia,=Al 2 Cl 3 -f 3NH 3 . 
The fluoride of aluminum can only be obtained by dissolving pure alumina 
in hydrofluoric acid ; it does not crystallize. This fluoride unites in two pro- 
portions with fluoride of potassium, for which it has a strong affinity. Both the 
compounds are gelatinous precipitates, which become white and pulverulent 
after being washed and dried. Berzelius assigns to them the formulae, 3KF+ 
A1 2 F 3 and 2KF-J-A1 2 F 3 . Fluoride of aluminum exists in two crystalline 
minerals, one of which, on account of its transparency, hardness and brilliancy 
is reckoned among the precious stones. They are, with their formulae after 
Berzelius : — 

Topaz . . . 3(Al 2 3 ,Si0 3 )+(AU0 3 +AUF 3 .) 
Pyknite . . 3(Al 2 ;i ,Si0 3 )+Al 2 F3. 

The Sulphocyanide. of aluminum crystallizes in oetohedrons, which arc 
persistent in air. 



SALTS OF ALUMINA. 

Sulphate of alumina; Al 2 3 ,3S0 3 + 18HO; 2145.8 -f- 2024.6, or 171.95 + 
162.23. — Obtained by dissolving alumina in sulphuric acid. It crystallizes 
with difficulty in thin flexible plates of a pearly lustre, has a sweet and astrin- 
gent taste, and is soluble in twice its weight of cold water, but does not dis- 
solve in alcohol. When heated it fuses in its water of crystallization, swells 
up, and forms a light porous mass, which appears at first to be insoluble in 
water, but dissolves completely after a time. Heated to redness it is entirely 
decomposed; the residue is pure alumina. This salt has been found in the 
crystalline form, in the volcanic island of Milo in the Archapelago. Sulphuric 
acid and alumina combine in several proportions, but this is considered the 
neutral sulphate, as it possesses the same number of atoms of acid, as it con- 
tains of atoms of oxygen in the base. 

Another sulphate of alumina (Al 2 3 ,3S0 3 -f-Al 2 3 ) is obtained, according 
to Maus, by saturating sulphuric acid with alumina, which contains twice as 
much alumina as the neutral sulphate. After evaporation this subsalt presents 
itself in a gummy mass, which dissolves in a small quantity of water, but is 
decomposed when the solution is diluted with a large quantity of water or 
boiled; in that case the neutral salt remains in solution, and the following salt 
precipitates. Subtrisulphate of alumina (A1 3 ,3S0 3 + 2A1 2 3 ) precipitates 
on adding ammonia to the sulphate of alumina, as a white insoluble powder, 
which is not decomposed by an excess of ammonia. It contains besides 46.9 
per cent, of water, or 9 atoms. This subsalt forms the mineral aluminife, 
which is found near Newhaven in England, and at Halle in Germany. 

Alum, sulphate of alumina and potash; KO,S0 3 -f A1„0 5 ,3S0 3 -f 24HO; 
3236.9+2700, or 259.38+216.— Sulphate of alumina has" a strong affinity for 
sulphate of potash, in consequence of which octohedral crystals of this double 
salt precipitate, whenever any salt of potash is added to a strong solution of 
sulphate of alumina. Alum is a salt of w r hich large quantities are consumed 
in dyeing. It is prepared by several processes, or derived from different 
sources. It may be prepared by decomposing clay with sulphuric acid; the 
decomposition is effected in the most complete manner by igniting pure clay, 
grinding it afterwards to powder and mixing it with 0.45 of sulphuric acid, of 
1.45 density. This mixture is heated in a reverberatory furnace till the mass 
31 



362 ALUMINUM. i 

becomes very thick; afterwards left to itself for at least a month, and then 
treated with water to wash out the sulphate of alumina formed. The addition 
of sulphate of potash converts the last salt into alum. But the mode of manu- 
facture just described has not been found so advantageous as the following", 
which alone is practised in this country. A series of beds occur low in many 
of the coal measures, which contain much bisulphuret of iron. One of these 
known as alum slate is a siliceous clay, containing a considerable portion of 
coaly matter, and of the metallic snlphuret in a state of minute division. 
When this mineral is exposed to air and moisture, it soon exfoliates, from the 
formation of sulphate of iron, the bisulphuret of iron absorbing oxygen like a 
pyrophorus. The excess of sulphuric acid formed attacks the other bases 
present, of which the most considerable is alumina. Aluminous schists often 
require to be moderately calcined or roasted, before they undergo this change 
in the atmosphere. The mineral being lixiviated, after a sufficient exposure, 
affords a solution of sulphate of alumina and protosulphate of iron from which 
the latter salt is first separated by crystallization. The subsequent addition of 
sulphate of potash to the liquor, causes the formation of alum; the chloride of 
potassium answers the same purpose, and has the advantage over the sulphate 
that it converts the remaining sulphates of iron into chlorides, which are very 
soluble, and from which the alum is most easily separated by crystallization. 
A very pure alum is obtained in the Roman states from alum-stone, which is 
simply heated till sulphurous acid begins to escape from it, and the residue of 
this calcination treated with water. This mineral contains an insoluble sub- 
sulphate of alumina with sulphate of potash. The heating has the effect of 
separating the excess of alumina, so that a neutral sulphate of alumina is 
formed. Alum-stone appears to be continually produced at the Solfatara near 
Naples, and other volcanic districts, by the joint action of sulphurous acid 
and oxygen upon trachyte, a volcanic rock composed almost entirely of fel- 
spar. 

Alum requires 18.4 parts of cold and only 0.75 parts of boiling water to 
dissolve it, and crystallizes very readily in regular octohedrons, of which the 
apices are always more or less truncated, from the appearance of faces of the 
p 1^1 cube. The taste of alum is sweet and astringent, and its action 
decidedly acid, and it dissolves metals, with evolution of hy- 
drogen, as readily as free sulphuric acid. The crystals efflo- 
resce slightly in air, and when heated melt in their water of 
L crystallization, which amounts to 45.5 per cent, of their weight 
or 24 atoms. The fused salt in losing this water, becomes 
viscid, froths greatly, and forms a light porous mass known as 
burnt alum. 

A pyrophorus is formed from an intimate mixture of 3 parts of alum and 1 
of sugar, which are first evaporated to dryness together, and then introduced 
into a small stoneware bottle, and this placed in a crucible and surrounded 
with sand. The whole is heated to redness till a blue flame appears at the 
mouth of the bottle, which is allowed to burn for a few minutes, and the mouth 
then closed by a stopper of chalk. After cooling, the bottle is found to contain 
a black powder, which becomes red hot when exposed to air; and catches fire 
also and burns with peculiar vivacity in oxygen gas. This property appears 
to depend upon the highly divided state of sulphuret of potassium, which is 
intermixed with charcoal and sulphate of alumina. A pyrophorus can be pro- 
duced from the sulphate of potash alone, without the sulphate of alumina, but 
it does not so certainly succeed. 

If the quantity of carbonate of soda, necessary to neutralize a portion of alum, 
be divided into three equal portions, and added in a gradual manner to the 
aluminous solution, it will be found that the alumina at first precipitated, is re* 




ALUM. 363 

dissolved upon stirring, and that no permanent precipitate is produced till 
nearly two parts of alkaline carbonate are added. It is in the condition of this 
partially neutralized solution that alum is generally applied as a mordant to 
cloth. Animal charcoal readily withdraws the excess of alumina from this so- 
lution, and so does vegetable fibre, probably from a similar attraction of sur- 
face. When this solution is concentrated by evaporation, alum crystallizes 
from it, generally in the cubic form and the excess of alumina is precipitated. 

Sulphate of ammonia may be substituted for sulphate of potash in this 
double salt, giving rise to ammoniacal alum, which agrees very closely in pro- 
perties with potash alum. 

Sulphate of alumina also combines with sulphate of soda forming soda alum, 
which crystallizes in the same form as common alum, and also contains 24HO. 
Crystals are obtained by mixing the constituent salts, and leaving a concen- 
trated solution to spontaneous evaporation; or by pouring spirits of wine upon 
the surface of such a solution contained in a bottle, which deposites crystals as 
the alcohol gradually diffuses through it. This salt effloresces in air, as rapidly 
as sulphate of soda. It is very soluble in water, 10 parts of water at 60° dis- 
solving 11 parts of this salt. 

Sulphate of alumina also combines with the sulphate of protoxide of iron, 
when dissolved with that salt and a considerable admixture of sulphuric acid 
(Klauer.) The double salt was found to contain i eq. protosulphate of iron 
(FeO,S0 3 ,) 1 eq. sulphate of alumina (Al 2 O v 3S0 3 ,) and 24 eq. of water 
(24HO,) which indicates a similarity in composition to alum. But it is depo- 
sited in long acicular crystals, which do not belong to the octohedral system, and 
has therefore no claim to be considered an alum. A similar salt with magnesia 
was obtained in the same way. Another combination of the same class, con- 
taining the sulphate of manganese, forms a white fibrous mineral found in a 
cave upon Bushman's river in south Africa. This salt has been carefully 
examined by Apjohn and by Kane, and found to contain 25HO. It is proba- 
ble that if the proportion of water in Klaur's salts were accurately determined, 
it would be found to be the same. These salts may be represented as com- 
pounds of a magnesian sulphate, retaining its single atom of constitutional wa- 
ter, with sulphate of alumina; the manganese compound thus: — 

MnO,S0 3 HO + Al 3 3 ,3SO+24HO. 

Certain salts have been formed, isomorphous with alum, and strictly analogous 
in composition, in which the alumina is replaced by metallic oxides isomor- 
phous with it, namely, by peroxide of iron, deutoxide of manganese, and ox- 
ide of chromium. To these salts the generic term alum is applied, and the 
species is distinguished by the name of the metallic peroxide it contains as 
iron alum, manganese alum, and chrome alum. 

Alumina dissolves freely in most acids, but like metallic peroxides in general 
it affords few crystalline salts, except double salts. The oxalate of potash and 
alumina is the only other of these that has been formed. It is remarkable for 
its composition, containing 3 eq. oxalate of potash to 1 eq. oxalate of alumina 
with 6 eq. of water. Its formula is, therefore, 

3(KO,C 2 3 ) + A] 2 3 ,3C 2 3 +6HO. 

Like alum it is the type of a genus of double salts. The corresponding oxalates- 
containing soda, crystallize with 1 OHO. — (Phil. Trans. 1837, p. 54.) 

Nitrate of alumina is said to crystallize with difficulty in prismatic crystals 
radiating from a centre. 

An insoluble phosphate of alumina precipitates when phosphate of soda is 
added to a solution of alum. By fusion it gives a glass like porcelain. Its 
composition is 2A1„0 3 ,3P0 5 (Berzelius.) This salt, dissolved in an acid and 



364 ALUMINUM. 

precipitated by ammonia in excess, gives a more highly basic phosphate, of 
which the formula is 4A1 2 3 ,3P0 5 (Berzelius.) The last salt occurs in nature, 
in combination with fluoride of aluminum, in the form of radiating crystals, con- 
taining 27.8 per cent, of water. It is the mineral wavellite, of which the formula 
is Al a F 3 +3(4Al 3 3 ,3P0 5 )+36HO. A phosphate of alumina and lithia, con- 
taining the same subphosphate of alumina, forms the rare mineral amblygonite, 
and may be prepared artificially. Its formula is 2LO,P0 5 -f 4A1 2 3 ,3P0 5 . 



SILICATES OF ALUMINA. 

The varieties of clay are essentially silicates of alumina, but composed as they 
are of the insoluble matter of various rocks destroyed by the action of water, it 
is not to be expected that they will be uniform in composition. Mitscherlich 
considers it very probable that the basis of clay is usually a subsilicate of alumina . 
of which the formula is 2Al 2 3 ,3Si0 3 ; and which contains 57.42 parts of silica 
and 42.58 of alumina in 100 parts. But from the analysis of Mosander, the re- 
fractory clay of Stourbridge (a fire-clay) is a neutral silicate of alumina, A1 2 3 , 
3Si0 3 . China-clay or kaolin, which is prepared from decaying granite, being 
the result of the decomposition of the felspar and mica of that mineral, is not 
uniform in its composition. 

A subsilicate of alumina exists, forming a very hard crystallized mineral. 
disihene or cyanite, of which the formula is 2Al 2 3 ,Si0 3 . 

Double silicates of alumina and potash are extensively diffused in the mineral 
kingdom, forming a very considerable portion of the solid crust of the globe, 
The most usual of these double salts is the following. 

Felspar is composed of single equivalents of the neutral silicates of potash 
and alumina. Its formula is therefore analogous to that of anhydrous alum, 
silicon being substituted for sulphur; K0,Si0 3 4-Al 2 3 ,3Si0 3 . It is one of the 
three principal constituents of granite and gneiss. 

Amphigen or leucite occurs principally in the lava of Vesuvius in a crystal- 
lized state. The relation between the potash and alumina is the same as in the 
preceding mineral, but it contains one-third less silica. Hence the formula 3K(X 
2Si0 3 -f 3(Al 2 3 ,2Si0 3 .) A similar combination is obtained by precipitating a 
saturated solution of alumina in potash, by a solution of silicate of potash (Ber- 
zelius.) 

When a mixture of silica and alumina is fused with an excess of potash, and 
the fused mass washed with water, to withdraw every thing soluble, a powder 
remains in which the potash and alumina are still in the ratio of single equivalents, 
but in which the oxygen of the silica is equal to that of the bases. This double 
salt has consequently the formula, 3KO,Si0 3 -j-3Al 2 O v 3Si0 3 . 

Mbite or soda felspar much resembles felspar in properties. Its composition 

is analogous, with the substitution of soda for potash ; NaO,Si0 3 -fAl 2 0^,3Si0 3 . 

Analcime is the soda silicate proportional to amphigen. It is crystallized like 

amphigen, but contains 8.27 per cent, or 6 atoms of water. Its formula is 3NaO, 

2Si0 3 -f3(Al 2 3 ,2Si0 3 ) + 6HO. 

A third compound may be prepared, corresponding with the artificial potash 
compound above. It occurs also in hexagonal prisms in the lava of Vesuvius, 
forming the mineral nephelin. Other silicates of soda and alumina are: — 
Mesofype or ncttroli/e, NaO,Si0 3 +3(Al 2 3 ,Si0 3 ) + 2HO. 
Sodalite, 3NaO,2Si0 3 -f 2(Al 2 3 ,Si0 3 .) The latter contains also chlorine. 
The two silicates of lithia and alumina are: — 
Pelalite, LO,2Si0 3 +Al 2 3 ,3Si0 3 . 
Triphane or Spodumene, LO,Si0 3 -f Al 2 3 2Si0 3 . 
Harmotome is a silicate of barytes and alumina, containing water. 



PORCELAIN. 365 

The silicates of lime and of alumina combine in many different proportions, 
forming a great variety of minerals. Most of them contain water, in consequence 
of which they froth when heated before the blow-pipe, and hence are called 
zeolites. One of these named stilbite, from its shining lustre, corresponds in 
composition with felspar, but contains in addition 6 atoms of water; its formula 
isCaO,Si0 3 -f Al 2 3 ,3Si0 3 4-6HO. A small portion of one or other of the 
alkalies is often found in these minerals, besides small quantities of protoxide of 
iron and other magnesian oxides, replacing, it may be presumed, the lime in 
part. This extensive class of minerals has been very fully studied by Dr. 
Thomson, who has added considerably to their number.* 

Silicate of alumina and magnesia, forms the mineral called soapstone, from 
its resemblance to mottled soap and being unctuous to the touch. The formula 
assigned to this mineral by Berzelius is 3MgO,2Si0 3 -f AI 2 3 ,2Si0 3 -!-6HO. 
The formula of dichroite, another combination of the same elements, is 3MgO. 
2Si0 3 + 3(Al 2 3 ,Si0 3 .) 



EARTHENWARE AND PORCELAIN 

The silicate of alumina is the basis of all the varieties of pottery. When 
moistened with water, clay possesses a high degree of plasticity, and can be 
extended into the thinnest plates, fashioned into form by the hand, by pressure 
in moulds; or, when dried to a certain point, be modelled on the turning lathe. 
It loses its water also in drying, without cracking, provided it is allowed to con- 
tract equally in all directions, and acquires greater solidity. When heated more 
strongly in the potter's kiln, in which it is not fused nor its particles agglutinated 
by partial fusion, it becomes a strong solid mass, which adheres to the tongue, 
and absorbs water with avidity. To render it impermeable by that liquid, it is 
covered with a vitreous matter, which is fused at a high temperature, and forms 
an insoluble glaze or varnish upon its surface. But the interior mass of ordinary 
pottery has always an earthy fracture, and presents no visible trace of fusion. 

When an addition is made to the clay, of some compound, which softens or 
fuses at the temperature at which the earthenware is fired, such as felspar in 
powder, then the clay is agglutinated by the fusible ingredient, and the mass i* 
rendered semi-transparent, in the same manner as paper that has imbibed 
melted wax remains translucent after the latter has fixed. The accidental 
presence of lime, potash, protoxide of iron, or any similar base in the clay, may 
produce the same effect by forming a fusible silicate diffused through the clay 
in excess. Such is the constitution of porcelain, and of brown salt-glaze ware 
of which soda-water bottles are made, which is indeed a sort of porcelain. 
When these kinds of ware are covered by a fusible material similar to that 
which has entered into the composition of their body, and a second time fired, 
they acquire a vitreous coating. Their fracture is vitreous and not earthy, the 
broken surface does not adhere to the tongue, and the mass has much greater 
solidity and strength than the former kinds of earthenware. In combining the 
ingredients of porcelain, an excess of the fusible ingredient is to be avoided, as 
it may cause the vessels to soften so much in the kiln as to lose their shape, or 
even to run down into a glass ; while on the other hand if the verifiable consti 
tuent is in too small a proportion, the heat of the furnace may be inadequate to 
soften the mass, and to agglutinate it completely. 

Porcelain. — The mode of fabricating porcelain, which has been known for a 
long time to the Chinese, was discovered in 1706 by Bottcher, at Dresden, 
where the art was first practised in Europe, and published afterwards by Reau- 

* Outlines of Mineralogy and Geology, vol. L 
31* 



366 



ALUMINUM. 



mur. The materials employed are (1) a fine and pure clay, prepared by levi- 
gation from mouldering granite or other disintegrated felspathic rocks. In China 
it is called kaolin. That consumed in the great potteries of Staffordshire is 
prepared in Cornwall, and known as china clay. A comparison of compact and 
disintegrated felspar, shows that by the solvent action of water, the latter has 
been deprived of half its silica, and above three-fourths of its potash. The 
silicate of alumina left, which forms the clay, is very difficult of fusion. The 
porcelain clay used at Berlin, which is extracted from the decomposed porphyry 
of Mori, contains, in 100 parts, 71.4 silica, 26 alumina, with small quantities of 
peroxide of iron, potash, and lime (Mitscherlich.) (2) Pure silica, which is pre- 
pared by heating chert or flint to redness, and quenching it in water. The 
mineral is afterwards obtained, by grinding and subsequent levigation, in a state 
of the greatest division. The clay and silica, both in the humid state, are then 
carefully intermixed. A body for the best kind of earthenware may be made of 
70 parts of the prepared clay and 24 of ground flint. But to form porcelain an 
addition is also made (3) of finely levigated felspar, to impart fusibility, the pro- 
portion necessary being learned by experiment. Phosphate of lime, sulphate of 
lime, and carbonate of lime are also added for the same purpose. A mixture of 
the prepared clay and felspar is also employed, without the introduction of silica. 
At Berlin, the porcelain earth of Mori is mixed with a quantity of felspar, which, 
it is said, amounts to about 32 per cent, without the addition of silica. At the 
royal pottery of Sevres, in France, the materials employed are felspar as it is 
found in three different states of decomposition, and which are technically termed 
sable cailloteux, sable argileux, and kaolin, the last being that in which the de- 
composition is most advanced, with small quantities of silica (sable d'Aumont) 
and chalk. They are combined in the following proportions: — 

Kaolin 70 

Sable cailloteux - - - 12 

Sable argileux - 9.18 

Sable d'Aumont - -".""'- 5.29 

Lime 3.53 (6.3 chalk.) 



100 



The body (pate) of the Sevres porcelain, so formed, consists very uniformly, 
according to M. Malaguti, in 100 parts, of— 

Silica - - - - 57 to 58 

Alumina ... 34.5 to 35 « 
Lime - 4.5 

Potash 3 

It forms a highly translucent and beautiful porcelain. Felspar mixed with a 
little clay is used as the glaze for this porcelain. Elsewhere a mixture of 
sulphate of lime, ground porcelain and flint is sometimes used as a glaze. In 
painting porcelain, the'kame metallic oxides are employed as in staining glass. 
They are combined with a vitrifiable material, generally made thin with oil of 
turpentine, and applied to the pottery sometimes under, and sometimes above 
the glaze. To fuse the latter colours, the porcelain must be exposed a third 
time to heat, in the enamel furnace. 

Stoneware. — The principal varieties of clay used here, according to Mr. 
Brande, are the following: — 1. Marly clay, which, with silica and alumina, 
contains a portion of carbonate of lime; it is much used in making pale bricks, 
and as a manure; and when highly heated enters into fusion. 2. Pipe clay. 



GLUCINUM. 367 

which is very plastic and tenacious, and requires a higher temperature than 
the preceding for fusion; when burned it is of a cream colour, and is used for 
tobacco-pipes and white pottery. 3. Potter's clay is of a reddish or gray 
colour, and becomes red when heated; it fuses at a bright red heat; mixed with 
sand it is manufactured into red bricks and tiles, and is also used for coarse 
pottery (Manual of Chemistry, p. 861.) The glaze is applied to articles of 
ordinary pottery after they are fired, and in the condition of biscuit ware. 
They are dipped into a mixture of about 60 parts of red lead, 10 of clay, and 
20 of ground flint diffused in water to a creamy consistence, and when taken 
out enough adheres to the piece to give a uniform glazing when again heated, 
To cover the red colour, which iron gives to the common clays when burnt, 
the body of the ware is sometimes coloured uniformly of a dull green, by an 
admixture of oxide of chromium, or made black by oxides of manganese and 
iron; or oxide of tin is added to the materials of the glaze, to render it white 
and opaque. The patterns on ordinary earthenware are generally first printed 
upon tissue paper, in an oily composition, from an engraved plate of copper, 
and afterwards transferred by applying the paper to the surface of the biscuit 
ware, to which the colour adheres. The paper is afterwards removed by a 
wet sponge. The fusion of the colouring matters takes place with that of the 
glaze, which is subsequently applied, in the second firing. The prevailing 
colours of these patterns are blue from oxide of cobalt, green from oxide of 
chromium, and pink from that compound of oxide of tin, lime, and a small 
quantity of oxide of chromium, known as pink colour. 



SECTION XI. 

GLUCINUM, YTTRIUM, THORIUM, ZIRCONIUM. 

GLUCINUM. 
Eq. 331.3 or 26.54; G. 

The compounds of this metal have a considerable analogy to those of alu- 
minum. Glucinum is obtained from its chloride, which is decomposed in the 
same manner as that of aluminum. This metal is fusible with great difficulty, 
not oxidable by air or water at the usual temperature, but it takes fire, in oxy- 
gen, at a red heat, and burns with a vivid light. It derives its name from 
yXvicvq, sweet, in allusion to the sweet taste of the salts of its oxide glucina. 

Glucina G 2 3 is a comparatively rare earth, but is contained to the ex- 
tent of 13| per cent, in the emerald or beryl, of which specimens that are not 
transparent or crystallized, can be procured in considerable quantity. To 
decompose this mineral, which is a silicate of glucina and alumina, it must be 
reduced to an extremely fine powder, the grosser particles which fall first 
when the powder is suspended in water, being submitted again to pulveriza- 
tion, and the powder fused with 3 times its weight of carbonate of potash. 
The calcined mass is moistened with water, and then treated with hydrochlo- 
ric acid, added in small portions till it is in excess. The potash, alumina and 
glucina are thus converted into chlorides, and dissolved. The solution is eva- 
porated to dryness on a water-bath, and the residue acidulated by a few drops 
of hydrochloric acid: the silica remains undissolved. The alumina and glucina 
are afterwards precipitated together from the solution, by ammonia; and after 
being well washed, but without being dried, the mixed oxides are digested in 



368 THORIUM. 

a large quantity of carbonate of ammonia, which takes up the glucina without 
touching the alumina. The liquor is filtered, and the carbonate of ammonia 
being then expelled from it by ebullition, carbonate of glucina precipitates. 
The earthy carbonate is ignited, and leaves glucina in the state of a white and 
light powder, tasteless, infusible, insoluble in water and ammonia, but soluble 
in potash and soda. Its density is nearly 3. It is distinguished from alumina, 
by forming a carbonate, and being soluble, when freshly precipitated, in a 
cold solution of carbonate of ammonia. 

Glucina combines with sulphuric acid in several proportions, forming a bi- 
sulphate G 2 3 ,6S0 3 , which is crystallizable, a neutral sulphate G 2 3 , 
3S0 3 , which may be obtained in solution, a soluble subsalt, G 2 3 ,2S0 3 , 
and an insoluble subsalt, G 2 3 ,S0 3 . 

Emerald or beryl is a silicate of the composition expressed by G 2 3 ,4Si0 3 
-f 2(Al 2 3 ,2Si0 3 .) This mineral crystallizes in six-sided prisms, which are 
very hard. When coloured green by oxide of chromium it forms the true 
emerald, and when colourless and transparent aqua marina, which are both 
ranked among the precious stones. The density of the emerald is 2.58 to 
2.732. 

Euclase is also a silicate of glucina and alumina, G 2 3 ,2Si0 3 4- 2(2A10 3 , 
Si0 3 .) It is a very rare mineral, which crystallizes in limpid, greenish 
prisms. 

Chrysoberyl, one of the finest of the gems, consists essentially of 1 atom of 
glucina combined with 6 atoms of alumina, G 2 3 ,6A1 2 3 . 



YTTRIUM. 
Eq. 402.5 or 32.25; Y. 

The earth yttria was discovered in 1794, by Gadolin, in a mineral from 
Ytterby in Sweden, which is now called gadolinite. It has since been found 
in several other minerals, but all of which are exceedingly rare. The metal 
was isolated from its chloride by Wohler, precisely in the same manner as 
the two preceding metals. It is of a darker colour than these metals, and in 
oxidability resembles glucinum. 

Yttria is considered a protoxide, Y'O. Its density is even greater than 
barytes, being 4.842. It is absolutely insoluble in the caustic alkalies, is pre- 
cipitated by yellow prussiate of potash, and its sulphate and some others of 
its salts have an amethystine tint, properties which distinguish it from the pre- 
ceding earths. 



THORIUM. 
Eq. 744.9 or 59.88; Th. 

This element was discovered by Berzelius, in 1824, in a black mineral, 
like obsidian, since called thorite, from the coast of the North Sea. This mi- 
neral contains 57 per cent, of thorina. This element has been named from 
the Scandinavian deity Thor. The metal was obtained from the chloride, 
and exhibited a general resemblance to aluminum. Like yttrium, it burns in 
oxygen with a degree of brilliancy which is quite extraordinary; the resulting 
oxide does not exhibit the slightest trace of fusion. 

Thorina is considered a protoxide, ThO. Its density is 9.402, and therefore 
superior to that of all other earths. It resembles yttria in being insoluble in 



ZIRCONIUM. 369 

alkalies, but differs from that earth in the peculiar property of its sulphate, to be 
precipitated by ebullition, and to re-dissolve entirely, although in a slow man- 
ner, in cold water. Its sulphate also forms a double salt with sulphate of 
potash, which dissolves in water, but is insoluble in a liquor saturated with sul- 
phate of potash. 



ZIRCONIUM. 
Eq. 420.2 or 33.67 ; Zr. 

Zirconium is obtained by heating the double fluoride of zirconium and potas- 
sium, with potassium, in a glass or iron tube. On throwing the cooled mass 
into water, the zirconium remains in the form of a black powder, very like that 
of charcoal. It contains an admixture of hydrate of zirconia, which may be 
withdrawn from it by digestion in hydrochloric acid, at 104° (40° cent.) The 
zirconium is afterwards washed with sal-ammoniac to remove completely chlo- 
ride of zirconium, and then with alcohol to withdraw the sal-ammoniac. If 
washed with pure water, it is apt to pass through the filter. After being thus 
treated, the powder assumes under the burnisher, the lustre of iron, and is com- 
pressed into scales which resembles graphite. When heated in air it takes fire 
below redness. It is very slightly attacked by either alkalies or acids, with the 
exception of hydrofluoric acid, which dissolves it with evolution of hycfrogen. 

The constitution of zirconia is not certainly known, but it is believed to be 
analogous to that of alumina, Zr 2 3 . It was first recognised as a peculiar 
earth by Klaproth in 1789, who discovered it in the zircon of Ceylon, a silicate of 
zirconia, which is also found in the syenitic mountains of the south-east side of 
Norway. The hyacinth is the same mineral of a red colour; it is found in vol- 
canic sand at Expailly in France, in Ceylon, and some other localities. The 
earth is obtained from this mineral, which is more difficult of decomposition 
than most others, by processes for which I must refer to Berzelius. (Traite, t. 
1, p. 329.) 

Zirconia is a white earth, like alumina in appearance, of density 4.3. Its hy- 
drate, after being boiled, is soluble with difficulty in acids. When heated it 
parts with its water, afterwards glows strongly, from a discharge of heat, be- 
comes denser and less susceptible of being acted on by reagents. It forms a 
carbonate. When once separated from its combinations, it is insolmble in car- 
bonate of potash or soda, but dissolves in them in the nascent state. The salts 
of zirconia have a purely astringent taste. It agrees with thorina in being pre- 
cipitated, when any of its neutral salts are boiled with a solution of sulphate of 
potash. 



370 MANGANESE. 



ORDER IV. 



METALS PROPER HAVING PROTOXIDES ISOMORPHOUS WITH 
MAGNESIA, WITH BISMUTH. 

SECTION I. 

MANGANESE. 

Eq. 345.9 or 27.72 ; Mn. 

9 

This element is found in the ashes of plants, the bones of animals, and in many 

minerals, of which that employed in the preparation of oxygen is one of the 
richest. The black oxide of manganese was long known as magnesia nigra, 
from a fancied relation to magnesia alba, but was first thoroughly studied by 
Scheele in 1774, and by Gahn immediately afterwards, who obtained from 
it the metal now named manganese. 

From its strong affinity for oxygen and the very high temperature which it 
requires for fusion, manganese is one of the metals proper, which is reduced 
and fused into a button with the greatest difficulty. Hydrogen and charcoal, 
at a red heat, reduce the superior oxides of this metal to the state of protoxide, 
without eliminating the pure metal at that temperature ; but at a white heat, 
charcoal deprives this metal of its whole oxygen. The following process is re- 
commended by M. John for the reduction of manganese : it illustrates the chief 
points to b£ attended to in the reduction of the less tractable metals. Instead 
of a native oxide, an artificial oxide of manganese, obtained by calcining the 
carbonate in a well-closed vessel, is operated upon. This oxide, which is pre- 
ferred from being in a high state of division, is mixed with oil and ignited in a 
covered crucible, so as to convert the oil into charcoal. After several repetitions 
of this treatment, the carbonaceous mass is reduced to powder, and made into 
a firm paste by kneading it with a little oil. Finally this paste is introduced into 
a crucible lined with charcoal (creuset brasque,) the unoccupied portion of 
which is filled up with charcoal powder. The crucible is first heated merely to 
redness for half an hour to dry the mass and decompose the oil, after which its 
cover is carefully luted down, and it is exposed for an hour and a half to the 
most violent heat of a wind-furnace, that the crucible itself can support without 
undergoing fusion. The metal is obtained in the form of a semiglobular mass 
or button in the lower part of the crucible, but not quite pure, as it contains 
traces of carbon and silicon derived from the ashes of the charcoal. By igniting 
the metal a second time in a charcoal crucible, with a portion of borax, John 
obtained it more fusible and brilliant, and so free from charcoal, that it left no> 
black powder when dissolved in an acid. 



OXIDES OF MANGANESE. . 371 

Manganese is a grayish white metal having the appearance of hard cast-iron. 
Its density according to John is 8.013; while M. Berthier finds it to be 7.05, 
and Bergman made it 6.850. From its close resemblance to iron, manganese 
may be expected to be susceptible of magnetism, but its magnetic powers are 
doubtful. Peclet has endeavoured to show that manganese can assume and 
preserve magnetic polarity from the temperature — 4° up to 70°, but that it 
loses it again at higher temperatures. The small difference between the atomic 
weights of iron, manganese, cobalt and nickel, which are respectively 339.2, 
345.9, 369 and 369.9, is remarkable, attended as it is by a great analogy be- 
tween these metals in many other respects. 

Manganese oxidates readily in air, soon falling down as a black powder ; in 
water it occasions a disengagement of hydrogen gas. It is best preserved in 
naphtha, like potassium, or over mercury. Manganese possesses five degrees 
of oxidation, with two intermediate or compound oxides. 



OXIDES OF MANGANESE. 



Protoxide of manganous 


oxide MnO. 


Deutoxide or manganic 


oxide 


Mn 2 3 . 


Peroxide 


. 


. Mn0 2 . 


Red oxide 


. 


. Mn 3 4 , 


Varvicite 


. 


. Mn t 7 , 


Manganic acid 




. MnO,. 


Hypermanganic acid 


• 


. Mn a 7 . 



or MnO-r-Mn„0 3 . 
orMn 2 0,-f 2MnO, 



Protoxide of manganese, Manganous oxide ; MnO, 445.9 or 35.72. — This 
is the oxide existing in the ordinary salts of manganese which are isomor- 
phous with the salts of magnesia. It may be obtained by fusing at a 
red heat in a platinum crucible, a mixture of equal parts of pure chlo- 
ride of manganese and carbonate of soda, b with a small quantity of sal- 
ammoniac. By the reaction between the first mentioned salts, chloride of sodium 
is produced and carbonate of manganese, which is decomposed at a red heat, 
leaving the protoxide of that metal. The hydrogen of the sal-ammoniac re- 
duces to the state of protoxide, at the same time, any peroxide which may be 
formed by absorption of oxygen from the air. Any one of the superior oxides 
of manganese, in the state of a fine powder, may be converted into protoxide 
by transmitting hydrogen gas over it, in a porcelain tube at a red heat ; the 
peroxide obtained by igniting the nitrate of the peroxide of manganese is 
recommended by Dr. Turner as the most easily deoxidated. The protoxide of 
manganese is a powder of a grayish green colour, more or less deep. When 
obtained by means of hydrogen at a low temperature, it absorbs oxygen from 
the air, soon becoming brown throughout its whole mass, and is, indeed, some* 
times a pyrophorus ; but when prepared by hydrogen at a high temperature, 
or prepared by means of an alkali, this oxide is permanent. It dissolves readily 
in acids, and is a strong base. When an alkali is added to a solution of its 
salts, protoxide of manganese is precipitated white, as a hydrate, which imme- 
diately absorbs oxygen from the air and becomes brown ; collected on a filter 
and washed, it ends by changing into a blackish brown powder, which is the 
hydrate of the deutoxide. A similar change is instantaneously produced by the 
action of chlorine- water upon the white hydrate, or by the addition of chloride 
of lime to a salt of the protoxide of manganese, but then the hydrated peroxide 
is formed. Protoxide of manganese resembles magnesia and protoxide of iron, 
in being precipitated by ammonia only in part. 



372 ' MANGANESE. 

Its salts are sometimes colourless, but more generally of a pale rose tint, 
which has been ascribed to a trace of manganic acid. But as the rose tint is 
not destroyed by sulphuretted hydrogen, it must be considered as a peculiar, 
although only occasional, character of manganous salts, (p. 125.) Solutions of 
the salts of manganese containing a strong acid in excess, are not precipitated 
by sulphuretted hydrogen. 

Protosulphuret of manganese may be procured in the dry way, by heating 
a mixture of deutoxide of manganese and sulphur. Sulphurous acid is disen- 
gaged, and a green powder remains, which dissolves in acids with disengage- 
ment of sulphuretted hydrogen. The same compound is obtained in the hu- 
mid way, when acetate of manganese is decomposed by sulphuretted hydrogen, 
or a manganous salt precipitated by an alkaline sulphuret. The precipitate is 
hydrated, and of an orange colour. When the protosulphate of manganese is 
decomposed by hydrogen at a red heat, it affords an oxisulphuret. 

Proto chloride of manganese; MnCl-|-4HO; 788.5+450 or 63.19+36. 
This salt crystallizes in thick tables, which are oblong and quadrilateral, of a 
rose colour, is very soluble in water and slightly deliquescent. The residuary 
liquid in preparing chlorine, by dissolving peroxide of manganese in hydro- 
chloric acid, consists of chloride of manganese contaminated by a portion of 
perchloride of iron. To remove the latter and obtain a pure chloride of man- 
ganese, the solution should be boiled down considerably, to expel the excess of 
acid, diluted afterwards with water and boiled again with carbonate of man- 
ganese, which salt precipitates the whole peroxide of iron, forming chloride of 
manganese with its acid (Mr. Everitt.) If about one fourth of the impure so- 
lution of chloride of manganese be reserved, and precipitated by carbonate of 
soda, a quantity of carbonate of manganese will be obtained, sufficient to pre- 
cipitate the iron from the other three-fourths of the liquid, and which may be 
used for that purpose after it has been washed. The chloride of ^manganese is 
precipitated white, when free from iron, without any shade of blue, by the fer- 
rocyanide of potassium. The crystals retain one, from their four equivalents of 
water, at 212° (Brandes,) but may be made anhydrous at a higher temperature. 
Brandes finds 100 parts of water to dissolve at 50°, 38.3 ; at 88°, 46.2°; at 144.5°, 
55 parts of the anhydrous salt. A higher temperature instead of increasing the 
solubility of this salt diminishes it. Absolute alcohol dissolves half its weight 
of the anhydrous chloride of manganese, and affords by evaporation in vacuo, 
a crystalline alcoate, containing two equivalents of alcohol. 

The correspondingy?t/or£c/e of manganese forms a double salt with fluoride 
of silicon, which is very soluble in water and crystallizes in long regular prisms 
of six sides. The formula of this double salt is, after Berzelius, 2SiF 3 -J-3MnF 
+21HO. 

Carbonate of manganese is a white insoluble powder, which acquires a 
brown tint when exposed in the dry state at 140°. It is decomposed by a red 
heat. Carbonate of manganese occurs in the mineral kingdom, but never in a 
state of purity, being mixed with the carbonates of lime and iron, which have 
the same crystalline form. Its presence in spathic carbonate of iron is said to 
be the cause, why the latter yields an iron peculiarly adapted for the manufac- 
ture of steel. 

Protosulphate of manganese; MnO, SO s +7HO. — A solution of this salt 
used in dying and entirely free from iron, is prepared by igniting the peroxide 
of manganese mixed with about one-tenth of its weight of pounded coal, in a 
gas retort. The protoxide thus formed is dissolved in sulphuric acid* with the 
addition at the end of a little hydrochloric acid ; the sulphate is evaporated to 
dryness and heated again to redness in the gas retort. The iron is found after 
ignition in the state of peroxide and insoluble, the persulphate of iron being de- 
composed, while the sulphate of manganese is not injured by the temperature 



DEUTOXIDEf OF MANGANESE. 273 

of ignition and remains soluble. The solution is of an amethystine colour, and 
does not crystallize readily. When cloth is passed through sulphate of manga- 
nese and afterwards through a caustic alkali, protoxide of manganese is pre- 
cipitated upon it, and rapidly becomes brown in the air, or it is peroxidized at 
once by passing the cloth through a solution of chloride of lime. The colour 
thus produced is called manganese brown. 

Crystallized under 42°, the sulphate of manganese gives crystals containing 
7HO, which have the same form as sulphate of iron. The crystals which form 
between 45° and 68°, contain 5HO, and are isomorphous with the sulphate of 
copper. By a higher temperature, from 68° to 86°, a third set of crystals are 
obtained, which contain 4HO, their form is a right rhombic prism. The sul- 
phate of iron and other sulphates also assume the same form (Mitscherlich.) 
This salt loses 3HO at 240°, but retains 1 eq. even at 400°, like the other 
magnesian sulphates. M. Kuhn finds, that when a strong solution of the sul- 
phate of manganese is mixed with sulphuric acid and evaporated by heat, a 
granular salt is precipitated, which contains only one equivalent of water. 
This sulphate also forms a double salt with sulphate of potash, which contains 
6HO. The anhydrous salt is soluble, according to Brandes, in 2 parts of 
water at 59°, in 1 part at 122°; but above the latter term, the salt becomes 
less soluble. It is insoluble in alcohol. 

Hypo sulphate of manganese (page 244,) is obtained by evaporation as a 
deliquescent saline mass. The peroxide of manganese used in preparing it, 
should be previously treated with nitric acid, to dissolve out the hydrated ox- 
ide, and be well washed. The oxalate of manganese, is a highly insoluble 
salt. The acetate is soluble in 3 2 parts of cold water, and also in alcohol. 
The bitartrate of potash dissolves protoxide of manganese, and forms a very 
soluble double salt, the tartrate of potash and manganese, which can be ob- 
tained, although with difficulty, in regular crystals. 

Deutoxide of manganese, Manganic oxide; Mn 2 3 ; 991.8 or 79,44. 
This oxide is left of a dark brown, almost black colour, when the nitrate of 
the protoxide is gently ignited. It also occurs crystallized in the mineral 
kingdom, although rarely; its density is 4.818, and it is named braunite as a 
mineral species. The hydrate of manganic oxide is formed by the oxidation 
in air of the manganous hydrate. The manganic hydrate also frequently 
occurs in nature of a black colour, both crystallized and amorphous, and is 
often mixed with the peroxide of manganese. It constitutes the mineral 
species manganite, of which the density is 4.3 to 4.4, and the formula Mn a 
3 , HO. This oxide colours glass of a red or violet colour. The common 
violet or purple stained glass, contains manganic oxide; also the amethyst. 

Manganic oxide is a base isomorphous with alumina and the peroxide of 
iron. It dissolves in cold hydrochloric acid, without decomposition, and in 
sulphuric acid, with a slight digestion. The manganic sulphate was found 
by Mitscherlich to form an alum, with sulphate of potash. Its solutions have 
a deep brown colour. At a higher temperature acids reduce the deutoxide of 
manganese to the state of protoxide, with evolution of oxygen gas. 

Sesqnichloride of manganese (Mn 2 Cl 3 ) is formed when the deutoxide is 
dissolved in hydrochloric acid at a low temperature. The solution is yellow- 
ish brown or black, according to its degree of concentration, and is decom- 
posed by a slight elevation of temperature, with evolution of chlorine. A 
corresponding sesquifluoride may be crystallized. 

Sesquicyanide of manganese. — A compound of this cyanide is formed, 

when the protacetate of manganese is mixed with hydrocyanic acid in excess, 

then neutralized with potash and evaporated; by the absorption of oxygen, the 

manganous cyanide is changed into hydrated manganic oxide and manganic 

32 



374 MANGANESE. 

cyanide, which last combines with cyanide of potassium, and appears, on the 
cooling of a concentrated solution, in red crystals, which dissolve easily in 
water, (Mitscherlich.) This salt is analogous to red prussiate of potash, con- 
taining manganese instead of iron, and may, therefore, be represented as con- 
taining manganicyanogen — a manganicyanide of potassium, K 3 -f(M 2 Cy 6 .) 
As a double cyanide, its formula would be, 3KCy-r-Mn 2 Cy 3 . 

Bed oxide of manganese, MnO, Mn 2 3 , named by Berzelius manganoso- 
manganic oxide, is produced at all times when any oxide of manganese is 
heated strongly in air. It is a double oxide, being a compound of single 
equivalents of protoxide and deutoxide of manganese. It forms the mineral 
hausmanite, which differs from manganite in having manganous oxide in the 
place of water. Its density is 4.722. Berthier finds that strong nitric acid 
dissolves out the protoxide of manganese from the red oxide, and leaves a 
remarkable hydrate of the peroxide, of which the formula is 4Mn0 o + HO. 

Peroxide of manganese, Black oxide of managanese; Mn0 2 ; 545.9 or 
43.72. — This is the familiar ore of manganese employed in the preparation of 
oxygen and chlorine. It generally occurs massive, of an earthy appearance, 
and contaminated with various substances such as peroxide of iron, silica and 
carbonate of lime; but sometimes of a fibrous texture, consisting of small 
prisms, radiating from a common centre. Its density varies from 4.819 to 
4.94; as a mineral species it has been named pyrolusi/e.* Another important 
variety of this ore, known as wad, is essentially a hydrate, containing 1 eq. of 
water to 2 eq. of peroxide, according to Dr. Turner. A hydrated peroxide, 
consisting of single equivalents of its constituents, is formed by precipitating 
the protosalts of manganese by chloride of lime; and the same compound re- 
sults from the decomposition of the acids of manganese, when diluted with 
water or an acid. It is possible that the equivalent of this oxide should be 
doubled, and that its proper formula is Mn 2 4 , corresponding with per- 
oxide of chlorine, ClO^. 

The peroxide of manganese, loses one-fourth of its oxygen at a low red 
heat and is changed into deutoxide; by the effect of a bright red heat it loses 
more oxygen, and becomes red oxide, the condition into which all the oxides 
of manganese pass when ignited strongly in the open air. The peroxide does 
not unite either with acids or with alkalies. When boiled with sulphuric acid 
it yields oxygen gas and a sulphate of the protoxide. In hydrochloric acid it 
dissolves with gentle digestion, evolving. chlorine gas, and forming protochlo- 
ride of manganese, (page 258.) It is extensively used in the arts for pre- 
paring chlorine, and also to preserve glass colourless by its oxidating action. 
In the last application, it is added to the vitreous materials in a relatively 
small proportion, and becomes protoxide, which is not a colouring oxide, 
while as deutoxide it would stain glass purple. At the same time it destroys 
carbonaceous matter, and converts protoxide of iron, which colours glass 
green, into peroxide which is less injurious. 

The mineral varvicile was discovered by Mr. Phillips among some ores of 
manganese from Hartshill in Warwickshire. It is distinguished from the perox- 
ide by being much harder, having more of a lamellated structure, and by yielding 
water freely when heated to redness. Its density is 4.531. It may be sup- 
posed to consist of 1 eq. of deutoxide, and 2 eq. of peroxide with 1 eq. of 
water (Dr. Turner;) its formula is, therefore, Mn 2 3 ,Mn 2 4 -f HO. 

* From Ttufi, fire, and xv* I wash, in allusion to its being employed to discharge the 
brown and green tints of glass. 



MANGANIC ACID. 375 



VALUATION OF PEROXIDE OF MANGANESE. 

The numerous applications of the higher oxides of manganese depending 
upon the oxygen which they can furnish, render it important to have the 
means of estimating expeditiously and without difficulty their value for sucli 
purposes. The value of these oxides is exactly proportional to the quantity 
of chlorine which they produce, when dissolved in hydrochloric acid, and the 
chlorine can be estimated by the quantity of protosulphate of iron, which it 
peroxidizes. Of pure peroxide of manganese 545.9 parts (1 eq.) produce 
442.6 parts of chlorine, which peroxidize 3456 parts (2 eq.) of crystallized 
protosulphate of iron (page 353.) Hence 50 grains of peroxide of manganese 
yield chlorine sufficient to peroxidize 317 grains (more exactly 316.5 grs.) of 
protosulphate of iron. 

Fifty grains of the powdered oxide of manganese to be examined are 
weighed out, and also any known quantity, not less than 317 grains, of the 
sulphate of iron (copperas) employed in chlorimetry. The oxide of manga- 
nese is thrown into a flask containing an ounce and a half of strong hydro- 
chloric acid, diluted with half an ounce of water, and a gentle heat applied. 
The sulphate of iron is gradually added in small quantities to the acid, so as 
to absorb the chlorine as it is evolved, and the addition of that salt continued 
till the liquid, after being heated, gives a blue precipitate with the red pussiate 
of potash, and has no smell of chlorine, which are indications that the proto- 
sulphate of iron is present in excess. By weighing what remains of the sul- 
phate of iron, the quantity added is ascertained; say m grains. If the whole 
manganese were peroxide, it would require 317 grains of sulphate of iron, and 
that quantity would, therefore, indicate 100 per cent, of peroxide in the spe- 
cimen; but if a portion of the manganese only is peroxide, it will consume a 
proportionally smaller quantity of the sulphate, which quantity will give the 
proportion of the peroxide, by the proportion: as 317 : 100 :: m : per centage 
required. The per centage of peroxide of manganese is thus obtained by 
multiplying the number of grains of sulphate of iron peroxidized, by 0.317. 

It also follows that the per centage of chlorine, which the same specimen of 
manganese would afford, is obtained by multiplying the number of grains of 
sulphate of iron peroxidized by 0.2588. 

Manganic acid; Mn0 3 ; 645.9 or 51.72. — When peroxide of manganese is 
strongly ignited with hydrate or carbonate of potash in excess, manganic acid 
is formed, under the influence of the alkali, together with a lower oxide of 
manganese. Ignition in open vessels or with an admixture of nitrate of potash, 
increases the production of the acid, by the absorption of oxygen which then 
occurs. The product has long been known as mineral chameleon, from the 
property of its solution, which is green at first, to pass rapidly through several 
shades of colour. But a more convenient process for preparing manganate of 
potash is that recommended by Dr. Gregory. He mixes intimately 4 parts ol 
peroxide of manganese in fine powder with 3$ parts of chlorate of potash, 
and adds them to 5 parts of hydrate of potash dissolved in a small quantity of 
water. The mixture is evaporated to dryness, powdered, and afterwards 
ignited in a platinum crucible, but not fused, at a low red heat. Digested in a 
small quantity of cold water, this affords a deep green solution of the alkaline 
manganate, which may be obtained in crystals of the same colour by evapo- 
rating the solution over sulphuric acid in the air-pump. The manganates 
were discovered by Mitscherlich to be isomorphous with the sulphates and 
chromates. It has not yet been found possible to isolate manganic acid. Its 



376 , MANGANESE. 

salts in solution readily undergo decomposition, unless an excess of alkali be 
present; and are also destroyed by contact of organic matter such as paper. 

Hypermanganic acid, Mn 2 7 ; 1391.8, or 111.44. — When the green solu- 
tion of manganate of potash, prepared as above directed, is diluted with boiling 
water, hydrated peroxide of manganese subsides, and the liquid becomes of a 
beautiful pink or violet colour. The manganic acid is resolved into peroxide 
manganese and hypermanganic acid: 

3Mn0 3 = Mn0 2 and Mn 2 7 . 

The hypermanganate of potash should be rapidly concentrated, without con- 
tact of organic matter, and allowed to crystallize. The crystals are of a dark 
purple colour, almost black, and soluble in sixteen times their weight of cold 
water; they were found by Mitscherlich to be isomorphous with hyperchlorate 
of potash. The hypermanganates give out oxygen when heated, and are re- 
converted into manganates. Their solutions have a rich purple colour, and 
are so stable that they may be boiled, if concentrated. A small portion of a 
hypermanganate imparts a purple colour to a very large quantity of water. 

The insoluble manganate of barytes may be formed by fusing peroxide of 
manganese with nitrate of barytes; and when mixed with a little water, and 
decomposed by an equivalent quantity of sulphuric acid, affords free hyper- 
manganic acid. In Mitscherlich's experiments, the free acid appeared to be a 
body not more stable than peroxide of hydrogen, being decomposed between 
86° and 104°, with the escape of oxygen gas and precipitation of hydrated per- 
oxide of manganese. It bleached powerfully, aud was rapidly destroyed by all 
kinds of organic matter. M. Huenefeld, on the other hand, obtained hyper- 
manganic acid in a state in which it could be preserved, evaporated, redis- 
solved, &c. He washed the manganate of barytes with hot water, by which 
it is resolved into peroxide of manganese and hypermanganate of potash, and 
then added to it the quantity of phosphoric acid exactly necessary to neutra- 
lize the barytes. The liberated hypermanganic acid was dissolved out, evapo- 
rated to dryness, and by a second solution* and evaporation, obtained in the 
form of a redish brown mass, crystalline and radiated, which exhibited the 
lustre of indigo at some points, and was entirely soluble in water. When dry 
hypermanganic acid was fused in a retort with anhydrous sulphuric acid, and 
afterwards distilled by a higher temperature, an acicular sublimate, of a crim- 
son red colour was obtained, which appeared to be a combination of hyper- 
manganic and sulphuric acids. (Berzelius's Traite, i. 522.) 

Hyperchloride of manganese, Mn 2 Cl 7 , is a greenish yellow gas, which 
condenses at zero into a liquid of a greenish brown colour. This liquid dif- 
fuses purple fumes, owing to the formation of hydrochloric and hyperman- 
ganic acids, by the decomposition of the moisture of the air. It was formed 
by Dumas by dissolving the manganate of potash in oil of vitriol, pouring the 
solution into a tubulated retort, and adding by degrees small portions of fused 
chloride of sodium or potassium, that is, salt completely free from water. The 
hyperchloride of manganese is the result of a reaction between the liberated 
hyoermanganic and hydrochloric acids: 

Mn 2 7 and 7HC1 = Mn 2 Cl 7 and 7HO. 

A corresponding hyperfluoride of manganese was formed by Wohler by- 
distilling, in a platinum retort, a mixture of manganate of potash and fluor spar 
in powder, with fuming sulphuric acid. It is a greenish yellow gas, which like- 
wise produces purple fumes in damp air. 



ISOMORPHOUS RELATIONS Of MANGANESE. 377 



ISOMORPHOUS RELATIONS OF MANGANESE. 

The compounds of no element enter into so many isomorphous groups, and 
connect so large a proportion of the elements by the tie of isomorphism as those 
of manganese. The salts of its protoxide are strictly isomorphous with the salts 
of magnesia and its class j so that manganese belongs to and represents the 
magnesian family of elements. The same metal connects the sulphur family 
with the magnesian, by the isomorphism of the sulphates and manganates ; and. 
therefore, sulphur, selenium, and tellurium, are thus allied to the magnesian 
metals. To these there may be occasion to add oxygen, if the reported dis- 
covery, by M. Persoz, of a class of hyposulphites isomorphous with the sulphates 
should prove to be correct. These hyposulphites are compounds of hyposul- 
phurous acid with basic sulphurets, and present a remarkable analogy, in solu- 
bility and other properties, to the sulphates, as well as similarity of form. Being 
sulphur salts, they are termed sulpho-sulphates by Persoz. The sulpho-sulphate 
of potash is formed by fusing 80 parts of sulphur with 100 parts of dry carbon- 
ate of potash, and washing out the sulphuret of potassium with alcohol. 

An equally interesting relation is that of hypermanganic with hyperchloric 
acid, and the isomorphism, which it establishes, of 2 equivalents of manganese 
with 1 equivalent of chlorine, and the other members of its family. We are thus 
enabled to place together for comparison the corresponding compounds of a 
magnesian metal or sulphur, and of chlorine, as in the following scheme: 

Metallic or Sulphur compound. Corresponding Chlorine compound 

Suboxide of copper, 

Manganous oxide, . 

Sulphurous acid, . 

Manganic oxide, 

Manganic acid, 

Peroxide of manganese, . 

Hyposulphuric acid, 

Hypermanganic acid, 

Although hyposulphuric acid is placed in relation with chloric acid, in the pre- 
ceding table, it is not known that the hyposulphates are isomorphous with the 
chlorates. It will be observed that the compounds deficient in the chlorine series 
are the analogues of those containing a single equivalent of manganese or sul- 
phur, and a compound of chlorine and oxygen resembling manganic oxide. 
The former deficiencies may be connected with the indivisibility of the equiva- 
lent of chlorine. 

That 2Mn, 2Zn, 2S, 20, 2H, &c, have the same value and character in com- 
bination as CI, is certainly a very remarkable circumstance. It suggests the 
idea, that it is by the intimate association or conjunction of two basyle atoms, 
that one salt-radical atom is produced ; and consequently that the basyle or 
salt-radical character of an elementary body is not absolute, but relative to the 
grouping of its atoms. In discussing the molecular condition of the metallic 
portions of the voltaic circle, (page 161) it was assumed that the ultimate atoms 
of a metallic mass are under the influence of chemical affinities, being in a state 
of chemical combination with one another, and not isolated and independent of 
each other, like loose grains of sand. The binary or saline structure of the 
metallic molecule there assumed, may be more precisely described by assigning 
to it three atoms of metal, two of which conjoined form the salt-radical or chlo- 
rous atom, and one the basyle or zincous atom. As this molecular theory 
modifies, in some degree, while it simplifies, and renders greatly more precise. 

32* 



Cu 2 


Hypochlorous acid, CIO. 


MnO 


Wanting. 


so 2 


Wanting. 


Mn 2 3 


Wanting. 


MnO, 


Wanting. 


Mn 2 0, 


Peroxide of chlorine, CIO 


S„0 5 


Chloric acid. CIO,. 


Mn 2 7 


Hyperchloric acid, C10 7 . 



378 ISOMORPHOUS RELATIONS OF MANGANESE. 

the view of voltaic action maintained in this work, I shall place in a note below 
a concise statement of the principles of that view, in its amended form.* 

* This modification of the chemical theory of the voltaic circle, which dispenses with 
any electrical hypothesis, is founded upon the three following postulates: 

I. The binary constitution of salts, which has already been fully discussed (page 130.) 
This applies to the fluid portions of the circle,-and its assumption is equally necessary on 
the usually received electro-chemical theory of the circle. 

II. The Sali. molecular structure of metals. — By this is meant that the metals are com. 
posed of molecules or groups of three atoms, having a binary or saline character, as ex- 
plained above. The metallic and fluid portions of the circle are thus assimilated in consti- 
tution. A decomposition can be propagated in any direction through the fluid portion of 
the circle, owing to the mobility of each particle, which permits it to take the new position 
required with a change of the direction in which the decomposing force is made to act, 
(page 1G1.) But decomposition is propagated, in both directions, through a chain of me- 
tallic molecules also, although solid, and therefore without the same power of adjustment. 
To explain this, it must be supposed that an internal decomposition can readily take place 
in the metallic molecule itself; that in respect of its three atoms, A, B and C, A forming 
the zincous element, and B-f-G the chlorous element, a change can easily occur, in which 
C becomes the zincous element of the sali-molecule, and A-f-B the chlorous element; that, 
supposing the three atoms of the molecules disposed in a line, A, B, C, any of its saline 
elements may be either to the right or left, as A-f-BC, or AB-J-C. The three atoms of the 
molecule being of one metal, and of the same nature, may admit of this change of internal 
arrangement, by a substitution of one atom for another. 

Several circumstances favour the idea of the existence of the assumed condition of 
metals: 1. In iron the susceptibility of magnetism is confined to the metal itself and one 
degree of oxidation, the black oxide, with its corresponding sulphuret. This is the degree 
of oxidation into which iron most readily passes; it consists of single equivalents of the 
protoxide and peroxide, or of three atoms of iron and four of oxygen. There is oxidation, 
in its formation, without disturbance of the metallic sali-molecule, Fe-}-Fe 2 ; the zincous 
element, Fe, combining with 1 eq. of oxygen, to form FeO, and the chlorous element, Fe 2 , 
with 3 eq. of oxygen, to form Fe 2 3 ; and these two oxides themselves remaining in a state 
of union. Metallic iron having, therefore, a common magnetic character with the black 
oxide of iron, or the loadstone, which has three atoms of metal in its molecule, may well be 
supposed to have three also. It is worthy of passing remark, that this double oxide is pe- 
culiar to the magnetic metals. It may not be an idle hope to look for the elucidation of 
the cause of magnetism in the peculiarities of the molecular structure of iron. 

2. It is supported by the disturbance of chemical affinities, or the electrical effects, con- 
sequent upon the contact of different metals; for one metal may be affected by another 
metal, admitting the reality of their sali-molecular structure, as well as by a salt or acid, 
the constitution of all these bodies being the same. When copper, for instance, touches 
zinc, the chlorous element of the copper molecule tends to leave its own zincous element, 
and to combine with the zincous element of the zinc molecule; so that a similar disturbance 
takes place as if the zinc were touched by hydrochloric acid. But the phenomena of the 
contact of metals belong to that class in which the chemical action stops short of combi- 
nation, the chlorous element of the copper molecule attracting its own zincous element the 
less that it attracts likewise the zincous element of the zinc, but not abandoning the former 
and combining with the latter. They belong to the class of the open, and not of the closed 
circuit. Sulphur, dry acids, peroxides, and many other bodies, disturb the molecular affi- 
nities of the metals they touch, in the same manner. The sali-molecule of the highly nega- 
tive metals, gold, platinum, mercury, &c, contains a strong salt-radical, united with a weak 
basyle, and resembles hydrochloric acid and the hydrates of the strong acids ; while the 
sali-molecule of the highly positive metals, potassium, zinc, &c, contains a powerful basyle 
and weak salt-radical, like the hydrated alkalies. In an alloy of two metals, the whole 
positive metal may exist as basyle, and the negative metal as salt-radical ; as in the crys- 
tallizable amalgam of cadmium, CdHg 2 . The sali-molecule of iron is difficult of decom- 
position, hence the unusual difficulty of alloying that with other metals, and the tendency 
of the iron molecule to combine, as a whole, as in the magnetic oxide. 

3. The reaction of the sali-molecules of different metals upon each other, when heated, 
appears to be the cause of the phenomena of thermo-electricity, (page 175,) but these are 
phenomena of the closed circle. It will be evident to those who are acquainted with the 
Contact Theory of galvanism, so ably developed by Ohm, and supported by the German 
electricians, and which embraces so happily the whole circle of the phenomena, that the 
chemical view, advocated here, although founded on a different fundamental assumption^ 



iron. 379 



SECTION II. 

IRON. 

Eq. 339.2 or 27.18; Fe (ferritin.) 

The most remarkable of the metals; the production of which, from the nume- 
rous and important applications it possesses, appears to be an indispensable con- 
dition of civilization. Meteoric masses of iron, often so pure as to be malleable, 
are found widely although thinly scattered over the earth's surface, and probably 

has a more perfect consistency and parallelism in its details with that theory than the electro- 
chemical theory, generally received, possesses. (Taylor's Scientific Memoirs, No. 7.) 

4. The relation of the phosphorus group of elements to the magnesian elements appear 
to be this : the equivalent of phosphorus, nitrogen, antimony and arsenic is equivalent to 
three magnesian atoms, and yet it is the least combining proportion of the elements enu- 
merated. This view, which was always probable, seems now rendered necessary by the 
observation of MM. Liebig and Dumas, that in the potash-tartrate of antimony strongly 
dried, 1 eq. of antimony replaces 3 eq. of hydrogen. Yet the elements of this triple molecule 
are not separable. In their individual action, however, we appear to have the cause of the 
singular tendency of the members of the phosphorus family to combine with three equiva- 
lents of other bodies, as with 3H, 30, 3Ni, 3Cu, 3Co, 3Hg, &c, and of the tribasic character 
of phosphoric, arsenic, and phosphorous acids. These elements, then, have an indissoluble 
sali-molecule. Metallic antimony also is isomorphous with tellurium, and connected, there- 
fore, through sulphur, with the magnesian family. 

5. Of the formation of molecular groups of atoms of the same element, apparently united 
by chemical affinity, it would not be difficult to multiply instances. Thus the atoms of 
sulphur appear to be associated in a molecular group composed of 12 atoms, when it pos. 
sess the crystalline form of bisulphate of potash ; for the integrant particle of' the salt con- 
tains not less than that number of atoms. Supposing aleo sulphur, in the state of vapour, 
to be similarly constituted, then, instead of one-third of a volume, its molecule will give 
four volumes of vapour, the most usual of all proportioBS. In crystallized sulphur, then, 
there may exist the same arrangement and aggregation of atoms as in bisuiphate of 
potash, resulting from the action of similar affinities. M. Liebig has represented KS 5 ,the 
pentasulphuret of potassium, by KS, SS 3 , or as a sort of sulphate of the sulphuret of po- 
tassium, which is quite in accordance with these molecular views. 

A change in the number of atoms forming the sulphur molecule, or in their arrange- 
ment, will account for the dimorphism of that body : indeed, inconstancy of molecular 
structure may be the general origin of dimorphism. In compound bodies, such as the 
acids, we have often illustrations of a similar association of several atoms. It appears, 
in the proportions in which they occasionally unite with bases, as in the terchromate of 
potash, the teriodate of soda, and may be inferred from the products of their decomposi- 
tion in other cases. Thus, when chlorate of potash is decomposed by sulphuric acid, 
three equivalents of that salt are decomposed together (page 268,) which is certainly a 
strong presumption that these three equivalents were previously associated in some way, 
forming one whole. On a similar presumption, Mitscherlich triples the equivalent of white 
precipitate, and makes it 3Hg Ad -j- 3Hg CI,) because that compound affords NHg 3 , as 
one of the products of its decomposition. It is certainly curious that the aggregation 
so indicated is very often that of three atoms, as if the atoms of compound bodies affected 
a salimolecular arrangement, similar to that assumed by the atoms of elements. 

III. The Rotal action of chemical affinity. — Chemical affinity is certainly capable of 
acting at a distance in a particular manner. The chemical affinity or characteristic 
attractive power of hydrogen, or of any other basyle, is a constant quantity. When the 
hydrogen is in combination with chlorine, as hydrochloric acid, that affinity is entirely 
engrossed by the chlorine. The chemical affinity of the chlorine, on the other hand, 
which is also a constant quantity, is then entirely engrossed by the hydrogen. But if an 
atom of zinc Zn, be brought in contact with a particular molecule of hydrochloric acid 
CI -f- H, then a portion of the affinity of CI is engaged by Zn, and diverted from H, which 
is proportionally relieved from that affinity. The unoccupied affinity of LI can act upon 
the CI' of an adjoining particle of hydrochloric acid; of which the H', in so far as it is re- 
lieved from its own CI', can attract the CI" of a third particle of hydrochloric acid, and 



380 



IRON. 



first attracted the attention of mankind to this metal. Of the occurrence of 
metallic iron as a terrestrial mineral in situ, the best established instances are 



the hydrogen H", of this third, the chlorine of a fourth, and thus an action be propagated 
in a rectilinear direction through the acid to a considerable distance from Zn, where it 
originated. The unoccupied affinity of the first H, instead of acting upon a single line of 
particles of hydrochloric acid as above supposed, may be divided among several lines of 
particles; these lines will radiate from a common centre Zn, being mutually repulsive of 
each other, for the same reason as the threads of iron filings attached to the pole of a magnet 
are so, (page 160.) As the number of lines and of particles of acid affected at any particu- 
lar distance from Zn, will increase with that distance, the action upon any one particle will 
necessarily diminish with its distance from the disturbing centre Zn, indeed it will be in 
the inverse ratio of the square of the particle's distance from Zn. 

A class of phenomena depending immediately upon the propagation of chemical affinity 
to a distance are those of cementation. When a compact mass of pure iron (a bar of the 
metal) is exposed to carbonic oxide gas, at a red heat, the superficial particles of iron de- 
compose that gas, by the exertion of a zincous affinity, taking carbon from the oxygen with 
which it is united, and becoming carburet of iron. But if exposure to the carbonic oxide 
be continued, the combined carbon does not remain at the surface of the iron, but travels 
inwards, diffusing itself through the metallic mass. It thus appears that when the iron 
Fe, of the superficial carburet, which we may represent by F -j- C is in contact with a 
second atom of carbon C, it attracts C', and C being proportionally relieved from the af- 
finity of Fe, may act upon the adjoining and interior atom of iron, Fe', and indeed com- 
bine with it, while the external atom Fe combines at the same time with C. The origi- 
nal atom of carbon C may thus combine in succession with a series of atoms of iron, Fe, 
Fe,' Fe'', &c, extending into the interior of the metallic mass, provided always that car- 
bon be constantly supplied to the external atom of iron Fe. Again, the steel may be de- 
carbonized, by exposing it to a source of oxygen, as by heating it in contact with oxide of 
iron, when the converse of what has been described occurs. The superficial particles of 
iron being deprived of their carbon, the balance of the attractive forces soliciting that 
element is turned, and it now travels in an outward direction, and abandons the iron en- 
tirely, if the external oxidating action is supported for a sufficient length of time. It is 
very obvious, from the phenomena of cementation, which are exhibited by a great variety 
of solid bodies besides iron, that a particle of carbon, when in combination with a particle of 
iron, may still attract and be attracted by the surrounding particle besides of that metal, 
and thus exercise an influence at a distance. 

The action of chemical affinity described in the preceding cases, as in direction recti- 
lineal, may very readily assume a circular direction or return upon 
itself. Thus, if two particles of hydrochloric acid, A and B, be dis- 
posed towards each other, with their unlike atoms together, as in Fig. 
102, it is obvious that, by an inconceivably minute expenditure of 
force, the h of A may be made to unite with the cl of B, while the k of B 
combines, at tbe same time, with the cl of A, or the combinations take 
place indicated by the brackets, and the two new molecules of hydro- 
chloric acid C and D are produced. It is impossible to prove the oc- 
currence of such a decomposition in molecules of the same kind, but 
we have it constantly illustrated in double decompositions where the 
molecules are different — as in hydrochloric acid and cyanide of silver, when the new pro- 
ducts, hydrocyanic acid and chloride of silver are formed, and demonstrate its occurrence 

by a sensible change. Now, instead of a pair of 
molecules of hydrochloric acid, we may have a circle 
composed of any number thus in contact, and under- 
going decomposition, as in the figure. For when the 
affinity of the cl of any acid molecule A (fig. 103) 
is engaged by h of the adjoining molecule B, to its 
left, the ft of A is proportionally relieved from the 
affinity of its own cl. The h of A is thus free to act 
upon the cl of the acid molecule C to its right; and 
the relieved hydrogen of that upon the chlorine of a 
third molecule to the right, and so on round the cir- 
f cle, as indicated by the brackets. When this action 
reaches B, the h of that molecule is thereby relieved 
from the attraction of its own cl, and on that account 
can the more readily combine with the cl of A. 
We pass at once from this to the voltaic circle, by 




Fig. 103. 




IRON ORES. 381 

the species of native iron which accompanies the Uralian platinum, and a thin 
vein about two inches in thickness, observed in chlorite slate, near Canaan in 
the United States. In a state of combination iron is extensively diffused, 
being found in small quantity in the soil, and in most minerals, and as sul- 
phuret, oxide and carbonate in quantities which afford an inexhaustible sup- 
ply of the metal and its preparations, for economical purposes. 

Iron differs from any other metal in two points, which greatly affect the 
methods of reducing it. Its particles agglutinate at a full red heat, although 
the pure metal is nearly infusible. The oxides of iron, which are easily re- 
duced by combustible matter, thus yield in the furnace a spongy metallic mass, 
which may admit of being compacted by subsequent heating and hammering, 
if the oxide has originally been free from earthy and other foreign matter, 
Such probably was every where the earliest mode of treating the ores of iron, 
and we find it still followed among rude nations. But iron is also singular in 
forming, at an elevated temperature, a fusible compound with carbon (cast 
iron,) the production of which facilitates the separation of the metal from 
every thing extraneous in the ore, and is the basis of the only method of ex- 
tracting iron, extensively practised. 

The ore of iron most abundant in the primary formations is the black oxide 
or magnetic ore, which affords the most celebrated and valuable irons of 
Sweden and the north of Europe; but of which the application is greatly 
circumscribed from its not being associated with coal. In the secondary and 
tertiary formations, the anhydrous and hydrated peroxide of iron, red and 
brown hematite, occur occasionally in considerable quantity, often massive, 
reniform, and quite pure, at other times pulverulent and mixed with clay. It 
is employed to some extent in England, in the last condition, but only for the 
purpose of mixing with the more common ore. The crystallized carbonate 
of iron, or spathic iron, is melted in some parts of the continent, and gives an 
iron often remarkable for a large proportion of manganese. The celebrated 
iron of Elba is derived from specular or oligistic iron, a crystallized peroxide. 
But the consumption of all these ores is inconsiderable, compared with that 
of the clay iron-stone of the coal measures. This is the carbonate of the pro- 
toxide of iron mixed with variable quantities of clay and carbonates of lime, 
magnesia, etc.; it is often called the argillaceous carbonate of iron. It is 
a sedimentary rock wholly without crystallization, resembling a dark coloured 
limestone, but of higher density, from 2.936 to 3.471, and not effervescing so 
strongly in an acid. It occurs in strata, beds or bands, as they are also named, 
from 2 to 10 or 14 inches in thickness, alternating with beds of coal, clay, 
bituminous schist, and often limestone. The proportion of iron in this ore, 
varies considerably, but averages about 30 per cent., and after it has been cal- 
cined, to expel carbonic acid and water about 40 per cent. r; 

supposing that part of these molecules are acid (A,) part zinc (B,) and part copper (C,) 
but all having the same binary or saline organization, and symmetrically placed in regard 
to each other. This, which I previously described as the inductive action of affinity from 
its analogy to magnetic induction, I now think may, with more propriety, be distinguished 
as the rotal action of affinity, and founded upon as a fundamental law of chemical affinity. 
Other applications will be found, for the molecular theory which it involves, in the sequel. 
* Accurate analyses of several Scotch varieties of this ore have been published by Dr. 
H. Colquhoun. Brewster's Journal, vii, 234 ; or Dr. Thomson's Outlines of Mineralogy 
and Geology, i, 446; and of the French ores by M. Bertheir, in his Traite des Essais par 
la Poie Seche, ii, 252, a work which is quite invaluable for the metallurgic student. 



382 



IRON. 



SMELTING CLAY IRONSTONE. 



The blast furnace, in which the ore is reduced, is of the form represented 
m the margin, 55 to 60 feet in height, with an interior diameter of from 14 to 
17 feet at the widest part. The cavity of the furnace is entirely filled with 
fuel, and the other materials, which are continuously supplied from an opening 



Fig. 104. 



near the top; and the combustion main 
tained by air thrown in at two or more 
openings, called twyeres near the bot- 
tom, under a pressure of about 6 inches 
of. mercury, from a blowing apparatus, 
so as to maintain the whole contents of 
the furnace in a state of intense ignition. 
When the air to support the combustion 
has attained a temperature of 600° or 
700°, by passing through heated iron 
tubes, before it is thrown into the fur- 
nace, raw coal may be used as the fuel; 
but with cold air, the coal must be pre- 
viously charred to expel its volatile mat- 
ter, and converted into coke, otherwise 
the heat produced by its combustion is 
insufficient. With the ore and fuel a 
third substance is added, generally lime- 
stone, the object of which is to form a 
fusible compound with the earthy mat- 
ter of the ore; it is, therefore, called a 
flux. Two liquid products accumulate 
at the bottom of the furnace, namely a 
glass composed of the flux in combina- 
tion with the earthy impurities of the 
ore, which when drawn off forms a solid 
slag, and the carburet of iron, or metal, 
which is the heavier of the two. It may be drawn from observations made bv 
Dr. Clark, in 1833, on the working of the Scotch blast furnaces, under the 
hot blast, that the relative proportions of the materials, including air,, and pro- 
duct of cast iron are as follows.* 




Weight. 

Coal 5 

Roasted iron stone. , 5 

Limestone. ......... 1 

Air 11 

Average product of cast iron. 2 

The ultimate fixed products are slag and carburet of iron, but the formation 
of these is preceded by several interesting changes, which the ore successively 
undergoes in the course of its descent in the furnace. A portion of the oxide 
of iron is certainly reduced to the metallic state, soon after its introduction, in 
the upper part of the furnace, by carbonic oxide and volatile combustible mat- 
ter; but the reduced metal does not then fuse. A large portion of the oxide 



Edinburgh Phil. Trans, vol. 13. 



SMELTING IRON. 383 

of iron must combine also, at the same time with the silica and alumina present 
in the ore, which act as acids, and a glass be formed, of which the oxide of 
iron is scarcely reducible by carbon. But this injurious effect of the acid 
earths is counteracted by the lime of the flux, which being a more powerful 
base than oxide of iron, liberates the oxide from the glass, and neutralizes the 
silica; so that the slag eventually becomes a silicate of lime and alumina, with 
scarcely a trace of oxide of iron, when the proportions of the materials intro- 
duced into the furnace are properly adjusted. The whole oxide of iron comes 
thus to be exposed to the reducing action of the volatile combustible, and con- 
sequently the whole iron is probably, at one time, in the condition of pure 
or malleable iron. But when the metal descends somewhat farther in the 
furnace, it attains the high temperature, at which it combines with the carbon 
of the coke in contact with it, and it fuses for the first time, in the form of car- 
buret of iron. It has not yet, however, attained its ultimate condition. When 
it reaches, in its descent, the region of the furnace where the heat is most in- 
tense, its carbon reacts on the silica, alumina, lime and other alkaline oxides 
contained in the fluid slag, with which it is accompanied, reducing portions of 
silicon, aluminum, calcium and other alkaline metals, which combine with the 
iron. The proportion of carbon replaced by silicon and metallic bases, is 
generally found to be greater in iron prepared by the hot than by the cold 
blast, owing, it is presumed, to the higher temperature of the furnace with the 
hot blast. 

The introduction of air already heated to support the combustion of the blast 
furnace, for which a patent was obtained by Mr. J. B. Neilson, has greatly re- 
duced the proportion of coal required to smelt a given weight of ore, enabling 
the iron master indeed, to effect a saving of more than three-fourths of the coal 
where that is of a bituminous quality. The air is heated between the blowing 
apparatus and the furnace, by being made to circulate through a set of arched 
tubes of moderate diameter, heated by a lire beneath them. The air can be heated 
in this manner to low redness, or to near 1000°, but there is found to be no 
proportional advantage in raising its temperature much above the melting point 
of lead (612°,) which is already higher than the point at which charcoal inflames. 
Considering the great weight of air that enters the furnace, the temperature of 
that material must greatly affect the whole temperature of the furnace, 
particularly of the lower part, where the air is admitted, and which part 
it is desirable should be hottest. Now a certain elevated temperature is 
required for the proper smelting of the ore, and unless attained in the 
furnace, the fuel is consumed to no purpose. The removal of the negative in- 
fluence of the low temperature of the air appears to permit the heat to rise to 
the proper point, which otherwise is attained with difficulty and by a wasteful 
consumption of fuel. Professor Reich, of Freiburg, has observed that heating 
the air likewise alters the relative temperatures of different parts of the furnace, 
depressing in particular, and bringing nearer the twyeres, the zone of highest 
temperature. The admixture of steam with the air has, he finds, precisely 
the opposite effect, elevating the zone of highest temperature in the furnace; 
so that the effect of the hot blast, may be exactly neutralized by mixing steam 
with the hot air. 

Cast iron. — The fused metal is run into channels formed in sand, and thus 
cast into ingots or pigs, as they are called. Cast iron is an exceedingly varia- 
ble mixture of reduced substances, of which the principal is iron combined 
with carbon. The theoretical constitution to which that variety of it, most 
definite in its composition, approaches, is the following: 



384 CAST IRON — MALLEABLE IRON. 



WHITE CAST IRON. 

Four atoms iron. 94.7 

One atom carbon 5.3 

100.0 

The difference in appearance and quality of the varieties of cast iron is not 
well accounted for by their composition. The gray or mottled cast iron, form- 
ing the qualities, Nos. 1 and 2, presents a fracture composed of small crystals, 
is easily cut by the file, and is preferred for castings. It is generally supposed 
that a portion of uncombined carbon is diffused through the iron of these 
qualities, in the form of graphite. No. 3, or white cast iron is more homoge- 
neous; its fracture exhibits crystalline plates, like that of antimony, and is 
nearly white; it is exceedingly hard and brittle. 

Mailable iron. — The great proportion of cast iron manufactured is afterwards 
refined, or converted into bar or malleable iron. Previous to refining, the cast- 
iron is always fused, and cooled suddenly by throwing water on the melted 
surface, by which it becomes white cast iron if not so before. In this condition 
it is most easily deprived of its carbon, which is the object of the refining. The 
principal operation, called the puddling process, consists in heating masses of 
the iron in a kind of reverberatory furnace with a certain access of air. The 
metal fuses, and by means of a sort of spatula is stirred about, and every part of 
it exposed to the flame. The carbon is thus gradually burnt out, partly by the 
direct action of oxygen in the flame, and partly by cementation with oxide of 
iron ; and the metal becomes less fusible but thick and tenacious, so that it sticks 
together, and is formed into a ball. In this condition it is removed by tongs, 
compressed into a cylindrical form by a few blows of a loaded hammer, and 
quickly converted into a bar by presssing it between grooved rollers. The 
tenacity of the metal is increased by welding several bars together ; a pile of 
bars brought to a full red heat in an oblong furnace, and then extended between 
the grooved rollers into a single bar. The texture of malleable iron is fibrous. 
Although the purest commercial form of the metal, it still contains about one-half 
per cent, of carbon, with traces of silicon and other metals. 

Steel. — Only the best qualities of malleable iron, those prepared from a pure 
ore, and reduced by means of charcoal, such as the Sweedish iron, are converted 
into steel. An iron box is filled with iron bars of such iron and charcoal powder, 
in alternate layers and kept at a red heat for forty-eight hours, or longer. The 
surface of the bars is found afterwards to be blistered, and they have absorbed 
from 1.3 to 1.75 per cent, of carbon. This is the process of cementation, to 
which allusion has already been made (Note, page 380.) It is known that iron 
can be converted into steel without being in actual contact with charcoal, pro- 
vided the iron and charcoal are in a close vessel together, and oxygen be 
present ; the carbon reaching the surface of the metal in the form of carbonic 
oxide gas. The iron becomes harder by this change and more fusible but can 
still be hammered into shape, and cut with a file. The property in which steel dif- 
fers most from soft iron, is the capacity it has acquired of becoming excessively 
hard and elastic when heated to redness and suddenly cooled by plunging it in 
water or oil. This hardness makes it invaluable for files, knives, and all kinds 
of cutting instruments. But the steel when hardened in the manner described, 
is harder than is required for most of its applications, and also very brittle. Any 
portion of its original softness can be restored to the steel by heating it up to 
particular temperatures, which are judged of by the colour of the film of oxide upon 
its surface, which passes from pale yellow at about 430°, through straw yellow, 



PASSIVE CONDITION OF IRON. 3S5 

brown yellow, and red purple into a deep blue at 580°, and allowing the steel 
afterwards to cool slowly. Articles of steel are tempered in this manner. 

Properties of iron. — Iron is of a bluish white colour, and admits of a high 
polish. It is remarkably maleable, particularly at a high temperature, and of 
great tenacity. Its mean destiny is 7.7, which is increased by fusion to 7.8439. 
When kept for a considerable time at a red heat, its particles often form large 
cubic or octohedral crystals, and the metal becomes brittle. Malleable iron 
softens before entering into fusion, and in this state it can be welded, or two 
pieces be united by hammering them together. The point of fusion of cast iron 
is 3479° ; that of malleable iron is much higher. Iron expands in becoming 
solid and therefore takes the impression of a mould with exactness. Iron is at- 
tracted by the magnet at all temperatures under an orange-red heat. It is then 
itself magnetic by induction but immediately loses it spolarity, if pure, when 
withdrawn from the magnet. If it contains carbon, as steel and cast iron, it is 
affected less strongly, but more durably, by the proximity of a magnet, be- 
coming then permanently magnetic. The black oxide, which forms the load- 
stone, and the corresponding sulphuret, are the only compounds of iron which 
share this property with the metal. A steel magnet loses its polarity at the 
boiling point of almond oil ; a loadstone, just below visible ignition (Faraday.) 

Iron reduced from the oxide by hydrogen at a heat under redness, forms a 
spongy mass, which takes fire spontaneously at the usual temperature, when 
exposed to air, and oxide of iron is reproduced (Magnus.) But iron, in mass, 
appears to undergo no change in dry air, and to be incapable of decomposing 
pure water at that temperature. Nor does it appear to be acted upon by 
oxygen and water together, but the presence of carbonic acid in the water, 
causes the iron to be rapidly oxidated with evolution of hydrogen gas. In 
the ordinary rusting of iron, the carbonate of the protoxide appears to be 
first produced, but that gradually passes into the hydrated peroxide, and the 
carbonic acid is evolved. The rust always contains ammonia, of which the 
hydrogen is imagined to come from the water decomposed; the native oxides 
of iron also contain ammonia. Iron remains bright in solutions of the alkalies 
and in lime-water, which appear to protect it from oxidation, but neutral 
and more particularly acid salts have the opposite effect. The corrosion of iron 
under water appears, in general to be immediately occasioned by the formation 
of a subsalt of that metal with excess of oxide, of which the acid is supplied by 
the saline matter in solution. Articles of iron may be completely defended from 
the injury occasioned in this way, by contact with the more positive metal, zinc, 
as in galvanized iron (page 170;) while the protecting metal itself wastes away 
very slowly. Cast iron is converted into a species of graphite, by many years 
immersion in sea-water, the greater part of the iron being dissolved while the 
carbon remains.* In open air, iron burns at a high temperature with vivacity, 
and its surface becomes covered with a fused oxide, which may afterwards be 
detached from it in scales, and forms smithy ashes. Iron also decomposes steam 
at a red heat, and the same oxide is formed as by the combustion of the metal 
in air, namely, the magnetic or black oxide, FeO-h Fe 2 O v 

Iron dissolves readily in diluted acids, by substitution for hydrogen, which is 
evolved as gas. Strong nitric acts violently upon iron, yielding oxygen to it, 
and undergoing decomposition. But the relations of iron to that acid, when 
slightly diluted, are exceedingly singular. They have been particularly studied 
by Professor Schcenbein. 

Passive condition of iron. — Pure malleable iron, such as a piece of clean 

* Mr. Mallet has collected much information respecting the corrosion of iron, in his 
First Report to the British Association, on the action of sea and river water upon cast and 
wrought iron. 1839. 
33 



386 iron. 

stocking wire, usually dissolves in nitric acid of sp. gr. 1.3 to 1.35, with elfer- 
vesence, but it may be thrown into a condition in which it is said by Schoenbein 
to be passive, as it is no longer dissolved by that acid, and may be preserved in 
it for any length of time without change : — 1. By oxidating the extremity of the 
wire slightly, by holding it for a few seconds in the flame of a lamp, and after it 
is cool, dipping it gradually in the nitric acid, introducing the oxidated end first. 
2. By dipping the extremity of the wire once or twice in concentrated nitric acid, 
and washing it with water. 3. By placing a platinum wire first in the acid, 
and introducing the iron wire, preserving it in contact with the former, which 
may afterwards be withdrawn. 4. A fresh iron wire may be introduced in the 
same manner into the nitric acid, in contact with a wire already passive ; this 
may render passive a third wire, and so on. 5. By making the wire the posi- 
tive pole or zincoid of a voltaic battery, introducing it after the negative pole or 
chloride has been placed in the acid. Oxygen gas is then evolved from the sur- 
face of the iron wire, without combining with it, as if the wire were of platinum. 
As the passive state can be communicated by contact of passive iron, so it may 
be destroyed by contact with active iron or zinc undergoing, at the moment, 
solution in the acid. If passive iron be made a negative pole (chlorous) in ni- 
tric acid, it also ceases to resist solution. The indifference to chemical action 
exhibited by iron when passive, is not confined to nitric acid of the density 
mentioned, but extends to various saline solutions which are usually acted upon 
by iron. An indifference to nitric acid of the same kind can also be acquired by 
other metals as well as iron, particularly bismuth (Dr. Andrews,) but in a much 
less degree. That the peculiar condition of the iron, which enables it to resist 
solution in the nitric acid, is of a voltaic nature cannot be doubted, but its exact 
character is still very imperfectly defined. In the consideration of the subject, 
the circumstance is not to be overlooked, that iron may, and does dissolve in ni- 
tric acid in two different ways : — (1) When directly oxidated by the decom- 
position of the acid and (2) by substitution for the hydrogen of the nitrate of 
water, as the same metal dissolves in oil of vitriol. The first mode of solution 
is not known to be connected with voltaic action, but the second is so, and 
should be promoted by rendering the iron positive or ziricous ; the condition 
which actually prevents all solution, makes iron passive in nitric acid of 1.3 
density. But if the predominating tendency of iron is to dissolve in acid of that 
.strength by direct oxidation, which is very probable, it comes to be a question 
whether increasing the disposition of the metal to dissolve in the other mode, or 
by substitution may not counteract the former tendency, and thereby impede 
the solution of the metal. The passive condition would then be represented as 
the result of an antagonism in the two forces which act simultaneously upon the 
metal.* Schoenbein has observed, however, an action of thin films or pellicles 
of foreign matter adhering to metallic surfaces, which he thinks, with reason, 
may be concerned in the phenomenon, and which is interesting independently 
of that relation. Platinum wire, after being plunged for a few seconds in hy- 
drogen gas, acts as a positive metal, or as if it were zinc, when associated with 
clean platinum in dilute sulphuric acid. This can be explained only by sup- 
posing combination of the hydrogen and platinum, and that the superficial polar 
molecule of the metal then consists of hydrogen as the external zincous 
element, and platinum as the chlorous element resembling the positive 
amalgam of zinc, in which zinc forms the external zincous atom, and 
mercury the chlorous atom of the molecule (page 163.) This hydro- 



* Dr. Andrews has indeed drawn the conclusion, from observation, that the ordinary 
chemical action of a hydrated acid upon the metals which dissolve in it, is in general di. 
minished when the acid is concentrated, by the voltaic association of these metals with 
such metals as gold, platinum, &c ; while on the contrary, it is increased when the acid is 
diluted.— Trans, of the Royal Irish Academy, 1838; or Becquerel, vol. v, pt. 2, p. 187. 



PROTOCOMPOUNDS OF IRON. 387 

gen must decompose the hydrated sulphuric acid (H-fS0 4 ,) evolving hydrogen 
and cause a train of decompositions from the hydruretted to the clean platinum. 
The analogy between this voltaic action of hydrogen, and the oxidation of hy- 
drogen gas by spongy platinum, adds to its interest. Again, platinum, gold and 
silver, by being placed for a few seconds in chlorine, become capable of acting 
negatively, or are chlorous, when they form a circle with clean platinum in di- 
lute sulphuric acid. Here, also, there must be a compound polar molecule, of 
which the zincous element is platinum, and the external chlorous element chlo- 
rine ; and this chlorine must combine with the hydrogen, and evolve the salt- 
radical of the hydrated acid, thus causing a train of decompositions through the 
latter. A pellicle of peroxide of lead can be precipitated upon the surface of 
iron and platinum, and then they become strongly chlorous in a voltaic circle, 
with nitric acid, like platinum with the film of chlorine above, till the pellicle of 
peroxide is dissolved off by the acid. Here the excess of oxygen in the perox- 
ide must decompose water, or more likely the hydrated acid present, evolving 
oxygen or the salt-radical of the acid, when the circuit is completed. In such 
circles, we have the affinity of hydrogen, of chlorine, or of oxygen, originating 
the rotal action, instead of that of a positive metal as usual* 



PROTOCOMPOUNDS OF IROX. 

Protoxide of iron, Ferrous oxide; FeO, 439.2 or 35.18. — Iron appears to 
admit of only two degrees of oxidation, the protoxide and peroxide, which are 
both basic, and correspond respectively with manganous and manganic oxides. 
The protoxide is not easily obtained in a dry state, from the avidity with 
which it absorbs oxygen. It exists in the sulphate and other salts of iron, 
formed when the metal dissolves in an acid with the evolution of hydrogen, 
and is precipitated as a white hydrate, when potash is added to these salts, 
which becomes black on boiling, from loss of water. The colour of the white 
precipitate changes by exposure to air to gray, then to green, bluish black, 
and finally to an ochrey-red, when it is entirely peroxide. 

The protoxide of iron is thrown down by alkalies as a hydrate, and by alkaline 
carbonates as a carbonate, which are white at first, but soon become of a dirty 
green, and undergo the same subsequent changes from oxidation. Its salts 
are not precipitated by sulphuretted hydrogen, the sulphuret of iron being dis- 
solved by strong acids, but give a black sulphuret with solutions of alkaline 
sulphurets. They give a white precipitate with the ferroeyanide of potas- 
sium, which gradually becomes of a deep blue when exposed to air; with the 
ferricyanide, a precipitate which is at once of an intense blue, being one of 
the varieties of Prussian blue. The infusion of gall-nuts does not affect a so- 
lution of the protoxide of iron when completely free from peroxide. 

Protosulphuret of iron is prepared by heating to redness, in a covered cruci- 
ble, a mixture of iron filings and crude sulphur, in the proportions of 7 of the 
former and 4 of the latter. It dissolves in sulphuric and hydrochloric acids 
with evolution of sulphuretted hydrogen gas (page 287-t) 

* Schcenbein ami Faraday in the Phil. Mag. 3rd Series, vols. 9, 10, 11, 12 and 14. 

t [As a hydrate, protosulphuret of iron is formed by precipitating a protosalt of iron 
by an alkaline protosulphuret. In this form it has lately been recommended by M. 
Mialhe as a valuable antidote for corrosive sublimate and the poisonous salts of lead and 
copper. To prepare the hydrated protosulphuret of iron, pure protosulphate of iron is to 
be dissolved in twenty-four parts of boiling- distilled water; this solution is to be precipi- 
tated by a sufficient quantity of protosulphuret of sodium likewise dissolved in boiled dis- 
tilled water. The protosulphuret is to be washed with pure boiled water, and kept in 
well-stopped bottles filled with distilled water, to prevent the action of the oxygen of the 



388 iron. 

A subsulphuret of iron, Fe 2 S, appears to be formed when the sulphate of 
iron is reduced by hydrogen; one-half of the sulphur coming off in the form 
of sulphurous acid. This subsulphuret will correspond with the subsulphu- 
rets of copper and lead, which crystallize in octohedrons. 

Protochloride of iron crystallizes with 4HO, and is very soluble. Like all 
the soluble protosalts of iron, it is of a green colour, gives a green solution, 
and has a great avidity for oxygen. 

Protiodide of iron is formed when iodine is digested with water and iron 
wire, the latter being in excess, and is obtained as a crystalline mass by evapo- 
rating to dryness. It has been introduced into medical use by Dr. A. T. Thom- 
son. A piece of iron wire is placed in the solution of this salt, to preserve it from 
oxidizing. The protiodide of iron dissolves a large quantity of iodine, with- 
out becoming periodide, as the excess of iodine may be precipitated by starch. 

Protocyanide of iron is obtained with the same difficulty as the protoxide 
of iron. When cyanide of potassium is added to a protosalt of iron, a yel- 
lowish red precipitate appears, which dissolves in an excess of the alkaline 
cyanide, and forms the ferrocyanide of potassium (page 318.) A gray powder 
remains on distilling the ferrocyanide of ammonium by a gentle heat; and a 
white insoluble substance on digesting recently precipitated prussian blue in sul- 
phuretted hydrogen water, contained in a well-stopped phial, which, although 
they differ considerably in properties, have both been looked upon as protocy- 
anide of iron. The most remarkable property of this cyanide is its tendency to 
combine with other cyanides of all classes, and to form double cyanides, or 
to enter as a constituent into the salt-radicals ferrocyanogen and ferricyanogen 
Cy 3 Fe, and Cy 6 Fe 2 . The two following compounds are obtained when the 
ferrocyanide and the ferricyanide of potassium are addded to a protosalt of 
iron. 

Ferrocyanide of potassium and iron; 3Fe.K-f-2(Cy 3 Fe.) — The bluish 
white precipitate which falls on testing a protosalt of iron with the ferrocy- 
anide of potassium or yellow prussiate of potash. Of the four equivalents of 
potassium contained in two equivalents of the latter salt (page 318,) three are 
replaced by three equivalents of iron in the formation of this precipitate, while 
the three potassium unite with the former salt-radical of the iron. This salt is 
represented above as consisting of 2 eq. of ferrocyanogen with 4 eq. of metal 
(3Fe-f-K,) ferrocyanogen being bibasic. Exposed to the air it absorbs oxy- 
gen, and becomes blue. It then affords ferrocyanide of potassium to water, 
and after all soluble salts are removed, a compound remains, which Liebig 
names the basic sesquiferrocyanidc of iron, and represents by the formula 
Fe_ 4 ,3(Cy 3 Fe)-f~Fe 2 3 , which corresponds, as will be seen afterwards, with 
1 eq. of prussian blue-j-1 eq. of peroxide of iron. This basic compound is 
dissolved entirely by continued washing, and affords a beautiful deep blue 
solution. The addition of any salt causes the separation of this compound. 
Tts solution may be evaporated to dryness without decomposition. 

Ferricyanide of iron, TumbuWs blup; 3Fe-f-(Cy 6 Fe 2 ). — This is the 
beautiful blue precipitate that falls on adding the ferricyanide of potassium 
(red prussiate of potash) to a protosalt of iron. It is formed by the substi- 
tution of 3 eq. of iron for the 3 eq. of potassium of the latter salt (page 318.) 
The same blue precipitate may be obtained by adding to a protosalt of iron, a 
mixture of yellow prussiate of potash, chloride of soda, and hydrochloric acid. 



air, by which it is quickly converted into a sulphate. Protosulphuret of iron acts as an 
antidote for corrosive sublimate, by converting it into cinnabar. One equivalent of pro- 
tosulphuret of iron and one of corrosive sublimate (FeSHgCl) become one equivalent of 
chloride of iron and one of cinnabar. (FeCIHgS) — Journ. de Phar. et Chim. Ser. III. 
t. 2, p. 315, and Am. Journ. of Pharm. vol. 14, p. 339. R. B] 



PROTOCOMPOUNDS OF IRON, 389 

The tint of this blue is lighter and more delicate than that of prusssian blue. 
It is occasionally used by the calico-printer, who mixes it with permuriate of 
tin, and prints the mixture, which is in a great measure soluble, upon Turkey 
red cloth, raising the. blue colour afterwards by passing the cloth through a 
solution of chloride of lime, containing an excess of lime. The chief object 
of that operation is indeed different, namely, to discharge the red and produce 
white patterns, where tartaric acid is printed upon the cloth, but it has also 
the effect incidentally of precipitating the blue pigment and peroxide of tin 
together on the cloth, by neutralizing the acid of the permuriate of tin. This 
blue is believed to resist the action of alkalies longer than ordinary prussian 
blue. Mr. R. C. Campbell observed that the ferricyanide of iron may be dis- 
tinguished from prussian blue by the circumstance, that when boiled in a so- 
lution of yellow prussiate of potash, it affords red prussiate of potash, which 
dissolves, and a gray insoluble residue of ferrocyanide of iron and ferrocyanide 
of potassium (Liebig.) 

Carbonate of iron is obtained on adding carbonate of soda to the protosul- 
phate of iron, as a white or greenish white precipitate, which may be washed 
and preserved in a humid condition in a close vessel, but cannot be dried with- 
out losing carbonic acid and becoming peroxide of iron. It is soluble, like the 
carbonate of lime, in carbonic acid water, and exists under that form in most 
natural chalybeates. Carbonate of iron occurs also crystallized in the rhom- 
boidal form of calc spar, forming the mineral spathic iron, which generallv 
contains portions of carbonates of lime, magnesia, and manganese. It is 
generally of a cream colour or black, and its density rarely exceeds 3.8. This 
anhydrous carbonate does not absorb oxygen from the air. Carbonate of iron 
is also the basis of clay-iron-stone. There is no carbonate of the peroxide. 

Sulphate of iron, Ferrous sulphate. Green vitriol, Copperas; FeO, S0 3 , 
HO + 6HO; 940.4+787.5 or 75.3+63.— This salt maybe formed by dis- 
solving iron in sulphuric acid diluted with 4 or 5 times its bulk of water, 
filtering the solution while hot, and setting it aside to crystallize. But the 
large quantities of sulphate of iron, consumed in the arts, are prepared simul- 
taneously with alum, by the oxidation of iron pyrites, (page 362.) 

The commercial salt is in large rhomboidal crystals, from an oblique rhom- 
boidal prism, which effloresce slightly in dry air, and when at all damp, ab- 
sorb oxygen, and become of a rusty red colour; hence the 
origin of the French term couperose applied to this salt, and 
corrupted in our language into copperas. If these crystals 
be crushed and deprived of all hygrometric moisture by 
strong pressure between folds of cotton cloth or filter paper, 
they may afterwards be preserved in a bottle without any 
change from oxidation. Of the 7HO which copperas con- 
tains, it loses 6HO at 238°, but retains 1 eq. even at 535°. 
It can be made, however, perfectly anhydrous, with proper 
caution, without any appreciable loss of acid. It was ob- 
served by Mitscherlich to crystallize at 176°, with 4HO, in 
a right rhombic prism, like the corresponding sulphate of manganese. When 
its solution, containing an excess of acid, is evaporated by heat, a saline crusr 
is deposited, which according to Kuhs, contains 3HO. Another hydrate has 
also been obtained by dissolving the sulphate in sulphuric acid, which contain- 
2HO, and has the crystalline form and sparing solubility of gypsum (Mit- 
scherlich.) The sulphate of iron appears to form neither acid nor basic salts 
One part of copperas requires to dissolve it; the following quantities of wa- 
ter, at the particular temperatures indicated above each quantity, according to 
the observations of Brandes and Firnhaber: 

33* 




390 IRON. 

50°— 59°— 75.2°— 109.4°— 114.8°— 140°— 183.2°— 194°— 212° 
1.64—1.43—0.87— 0.66 — 0.44—0.38— 0.37 —0.27—0.30 

The sulphate of iron undergoes decomposition at a red heat, changes into 
sulphate of the peroxide, and leaves, after all the acid is expelled, the red per- 
oxide known as colcothar. This sulphate, like all the magnesian sulphates, 
forms a double salt with sulphate of potash, containing 6HO. A solution of 
the sulphate of iron absorbs nitric oxide, and becomes quite black; it takes up 
the gas in the proportion of 9 parts to 100 anhydrous salt, according to Peli- 
got, or one-fourth of an equivalent (page 214.) 

Protonitrate of iron may be formed by dissolving the protosulphuret of iron 
in nitric acid, diluted and cold; the solution evaporated in vacuo gives pale 
green crystals, which are very soluble. The solution of the neutral salt is 
decomposed near the boiling temperature; with the evolution of nitric oxide, 
and the precipitation of a subnitrate of the peroxide in abundance. Iron turn- 
ings dissolve in pure nitric acid, and form the same salt, without the evolution 
of any gas, the water and acid undergoing decomposition, so as to produce 
ammonia, while they oxidate the iron. 

Protacetate of iron is obtained by dissolving the metal or its sulphuret 
in acetic acid. It forms small green prisms, which decompose very readily 
in the air. 

Tartrate of potash and iron is prepared by boiling bitartrate of potash with 
half its weight of iron turnings and a small quantity of water. Hydrogen gas 
is evolved, and a white, granular and sparingly soluble salt is formed, which 
blackens in air from absorption of oxygen. It is used medicinally. The 
iron of this salt is not precipitated either by hydrate or carbonate of potash. 

The titanate of iron occurs in masses of a metallic black, or as black grains 
in volcanic sand. It crystallizes in the form of peroxide of iron, (page 122,) 
with which it is often mixed. Its formula is FeO,Ti0 2 . 



PERCOMPOUNDS OF IRON. 

Peroxide of iron, Sesquioxide of iron, Ferric oxide, Fe 2 3 ; 978.4 or 
78.36. — Occurs in great abundance in nature: 1. As oligistic or specular iron, in 
crystals derived from a rhomboid very near the cube, which are of a brilliant 
metallic black and often iridescent. Their powder is red; their density from 
5.01 to 5.22. This forms the celebrated Elba ore. 2. As red hematite, in 
fibrous, mamillated, or kidney-shaped masses, of a dull red and very hard, of 
which the density is from 4.8 to 5.0. This mineral is cut, and forms the 
burnishers of blood-stone. 3. Also in combination with water, as brown 
hematite, which is much more abundantly diffused than the anhydrous perox- 
ide, the granular variety supplying, according to M. Berthier, more than three- 
fourths of the iron furnaces in France. Its density is 3.922, its powder brown, 
with a shade of yellow, and it dissolves readily in acids, which the anhydrous 
peroxide does not. From analyses of Dr. Thomson and M. Berthier, this 
mineral occurs with 1 eq. of water, or HO,Fe- 2 3 , analogous to the magnetic 
oxide of iron, FeO,Fe 2 3 .* The hydrated peroxide produced by the oxida- 
tion of iron pyrites, of which it retains the form, contains 1 eq. of water, or 
10.31 per cent, and that from the oxidation of the carbonate of iron, 3 eq. of 
water, or 14.71 per cent, to 2 eq. of peroxide, (Mitscherlich, Lehrbuch, II. 23, 

* One of the hydrates, probably this one, occurs very rarely crystallized in very small 
crystals, derived from the cube or octohedron, (Berthier, Traite, II. 225,) that is, in the form 
of the magnetic oxide of iron — a circumstance of great interest, if it is an instance of the 
isomorphism of hydrogen with iron or a magnesian metal. 



PERCOMPOUNDS OF IRON. 391 

1840.) The hydrate is the yellow colouring matter of clay, and with silica 
and clay it forms the varieties of ochre. 

When metallic iron is oxidated gradually in a large quantity of water, there 
forms around it a light precipitate of a bright orange yellow, which is a ferric 
hydrate, according to Berzelius, and of which the empirical formula is 2Fe 2 
3 4-3HO, the usual composition of brown hematite. When iron is oxidated 
in deep water, it is converted, according to Mr. E. Davy, into the magnetic 
oxide, which is possibly formed by cementation from the hydrated peroxide. 
The hydrated peroxide is also obtained, by precipitation from the persalts of 
the metal, by ammonia and by a hydrated or carbonated alkali; but never pure, 
as when an insufficient quantity of alkali is added, a subsalt containing acid 
falls, and when the alkali is added in excess, a portion of it goes down in com- 
bination with the peroxide, and cannot be entirely removed by washing. When 
ammonia is used, the water and excess of the precipitant can be expelled by 
ignition, and the pure peroxide obtained.* The latter is not magnetic, and after 
ignition dissolves with difficulty in acids. When ignited strongly, it loses oxy- 
gen and becomes magnetic. 

The peroxide of iron and its compounds are strictly isomorphous with alu- 
mina and the compounds of that earth, and remarkably analogous to them in 
properties. It is a weak base, of which the salts have a strong acid reaction, 
and are decomposed by all the magnesian carbonates, as well as by the mag- 
nesian oxides themselves. The solution of its salts, which are neutral in com- 
position, have generally a yellow tint, but they are all capable, when rather 
concentrated, of dissolving a great excess of peroxide and then become red. 
Very dilute solutions of the neutral salts of peroxide of iron are decomposed 
by ebullition, and the peroxide entirely precipitated, the acid of the salt then 
uniting with water as a base, (Scheerer.) 

Iron is most conveniently distinguished by tests, or precipitated for its 
quantitative estimation, when in the state of peroxide. The solution of a 
protosalt is usually peroxidized by transmitting a current of chlorine throuo-h 
it, or by adding to it, at the boiling point, nitric acid, in small quantities, so 
long as effervescence is occasioned from the escape of nitric oxide. Alkalies 
and alkaline carbonates precipitate the peroxide in the state of hydrate. Sul- 
phuretted hydrogen converts a persalt of iron into a protosalt, with precipita- 
tion of sulphur. The ferrocyanide of potassium throws down prussian blue, 
but the ferricyanide has no effect upon a persalt of iron. The sulphocyanide 
of potassium produces a deep wine-red solution with a persalt of iron, which 
becomes perfectly colourless when considerably diluted with water, provided 
the salt of iron is not in great excess. Infusion of nut-galls produces a bluish 
black precipitate — the basis of common writing ink. 

Black or magnetic oxide of iron, FeO,Fe20 3 , called also the ferroso-ferric 
oxide, an important ore of iron, is a compound of the two oxides. It crystallizes 
in the regular octohedron. In this compound, the peroxide of iron may be re- 
placed by alumina and by oxide of chromium, and the protoxide of iron by 
oxide of zinc, magnesia, and protoxide of manganese, without change of form. 
It was produced artificially, by Liebig and Wohler, by mixing the dry proto- 



* [In the pulpy state as precipitated by an excess of ammonia, this hydrate is a valuable 
antidote for the acids of arsenic. It is to be prepared by precipitating the neutral persul- 
phate, (p. 393,) by a solution of ammonia, washing the precipitate and preserving 1 it under 
and merely covered by water. As first produced it is bulky and of a dull brown colour; 
by keeping, it gradually shrinks in volume and becomes deep reddish brown. The antidote 
is most efficacious in its recent state; the above changes being accompanied by some loss 
of power as evinced by the experiments of Mr. Procter. (Amer. Journ. of Pharmacy, vol. 
14, p. 29.) This is probably due to a closer cohesion of the particles and not to any loss 
of water. R. B.l 



392 iron. 

chloride of iron with an excess of carbonate of soda, calcining the mixture in 
a crucible, and treating the mass with water. The double oxide remains as a 
black powder, which may be washed and dried without its oxidating farther. 
The same chemists, by dissolving the black oxide in hydrochloric acid, and 
precipitating by ammonia, obtained a hydrate of the double oxide. It was at- 
tracted by a magnet, even when a flocculent precipitate suspended in water. 
When ignited and anhydrous, this double oxide is much more magnetic than 
iron itself. 

Sesquisulphuret of iron, or Ferric sulphuret, Fe 2 S 3 , corresponding with 
the peroxide, may be prepared by pouring, drop by drop, a solution of per- 
salt of iron, into a solution of an alkaline sulphuret, the last being preserved 
in excess. At a low red heat, it loses 2-9ths of its sulphur and becomes mag- 
netic pyrites. The common yellow iron pyrites is the bisulphuret of iron. 
It crystallizes in the cube or other forms of the regular system, its density is 
4.981. It may be formed artificially by mixing the protosulphuret with half 
its weight of sulphur, and distilling in a retort by a temperature short of red- 
ness. The metallic sulphuret combines with a quantity of sulphur equal to 
what it already possesses, and forms a bulky powder of a deep yellow colour 
and metallic lustre, upon which sulphuric and hydrochloric acids have no ac- 
tion. This sulphuret appears to be of a stable nature, but the lower sulphurets 
of iron oxidate, when moistened, with great avidity. Stromeyer found the na- 
tive magnetic sulphuret of iron to consist of 100 parts of iron combined with 
68 of sulphur; and the sulphuret left on distilling iron with sulphur, at a high 
temperature, to be of the same composition. It may be viewed as 5FeS-f- 
Fe 2 S 3 (Berzelius.) It is said to be this compound which is almost always 
formed when sulphuret of iron is prepared. 

Per chloride of iron, Fe 2 Cl 3 , is formed when iron is burned in an excess of 
chlorine. It is volatile at a red heat. Its solution, which is used in medicine, 
is obtained by dissolving the hydrated peroxide of iron in diluted hydrochloric 
acid. When greatly concentrated, the solution of perchloride of iron yields at 
one time orange yellow crystalline needles, radiating from a centre, which are 
Fe 2 Cl 3 4- 12HO; at another time, large dark yellowish red crystals, Fe 2 Cl 3 4- 
5HO (Mitscherlich, Lehrbuch II. 498.) Mixed with sal ammoniac, and evapo- 
rated in vacuo, it affords beautiful ruby red octohedral crystals, consisting of 2 
eq. of chloride of ammonium, and 1 eq. perchloride of iron, with 2 eq. of water r 
Fe 2 Cl 3 ,2NH 4 Cl-h2HO. Of this water, the double salt, I find, loses 1 eq. at 
150°, and the other when dried above 300°. There is a similar double salt, 
containing chloride of potassium, but not so easily formed. The perchloride of 
iron is soluble both in alcohol and ether. A strong aqueous solution was found 
by Mr. Phillips to dissolve not less than 4 eq. of freshly precipitated hydrated 
peroxide of iron, becoming deep red and opaque. 

Periodide of iron is formed in similar circumstances as the preceding per- 
chloride. 

Percyanide, or sesqwcyanide of iron, Fe 2 Cy 3 , is unknown in a pure state. 
A solution of it, which is decomposed by evaporation, is obtained by precipi- 
tating the potash of the red prussiate by the fluoride of silicon. It forms a 
numerous class of double cyanides. A compound of the two cyanides of iron, 
like the compound oxide, is obtained as a green powder, when a solution of the 
yellow prussiate of potash, charged with an excess of chlorine, is heated or ex- 
posed to air. The precipitate should be boiled with eight or ten times its weight 
of concentrated hydrochloric acid, and well washed. Its formula is, FeCy, Fe 2 
Cy 3 +4HO.* 

* Pelouze, An. de Ch. et de Ph. t. 69, p. 40. 



PERSALTS OF IRON. 393 

Sesquiferrocyanide of iron, Prussian blue, Fe 4 , 3(Cy 3 Fe.) — This remark- 
able substance precipitates whenever the yellow prussiate of potash is added 
to a persalt of iron. For the preparation of prussian blue in quantity, Liebig 
recommends the following process of Hochsteller. Six parts of green vitriol 
and six parts of yellow prussiate of potash to be dissolved, each by itself, in 
fifteen parts of water, the solutions mixed, and an addition then made to them 
of one part of oil of vitriol, and twenty-four parts of strong hydrochloric acid. 
After some hours, a clear solution of one part of chloride of lime in eighty 
parts of water is gradually added, by small portions, observing the precaution 
to stop as soon as an effervescence is observed, from the disengagement of 
chlorine. After being allowed to subside for several hours, the precipitate is 
washed and dried at the usual temperature, or by artificial heat. It is said that 
the finest colour is obtained by heating the precipitate with dilute nitric acid, 
till it acquires a deep blue colour, instead of oxidizing by chlorine. 

Prussian blue, dried at the temperature of the air, is a light porous body, of 
a rich velvety blue colour; dried at a higher temperature, it is more compact, 
and exhibits in mass a coppery lustre. It is tasteless, and not poisonous. 
Alkalies decompose it, precipitating peroxide of iron and reproducing an alka- 
line ferrocyanide. This renders prussian blue of little value in dying, as it 
is injured by washing with soap. Red oxide of mercury, boiled with prussian 
blue, affords the soluble cyanide of mercury, with an insoluble mixture of oxide 
and cyanide of iron. It is destroyed by fuming nitric acid, but combines 
with oil of vitriol, forming a white pasty mass, which is decomposed by 
water. 

In the formula above, prussian blue is represented as consisting of 4 eq. of 
iron and 3 eq. of the bibasic salt-radical, ferrocyanogen, and, therefore, named 
a sesquiferrocyanide. It contains oxygen and hydrogen, besides, which can- 
not be separated without the decomposition of the compound. In its forma- 
tion 3 eq. of ferrocyanide of potassium react upon 2 eq. of a persalt of iron. 
Thus supposing the ferrocyanide of potassium and perchloride of iron to be 
mixed: 

OK-f 3(Cy 3 Fe) and 4Fe + 6Cl = 4Fe + 3(Cy Fe) and 6KC1. 

In precipitating prussian blue, care should be taken to avoid an excess of the 
ferrocvanide of potassium, as the precipitate is apt to carry down a portion of 
that salt. The combination of prussian blue and peroxide of iron, called basic 
prussian blue, was noticed at page 388. 

Although there is no carbonate of the peroxide of iron, the hydrated per- 
oxide is dissolved by alkaline bicarbonates, under certain conditions, which 
are not well understood, and a red solution is formed. 

Persidphates of iron. — The neutral persulphate, Fe 2 3 ,3SO ;! , is formed 
by adding to a solution of the protosulphate half as much sulphuric acid as it 
already contains, and peroxidizing by nitric acid. It gives a syrupy liquid, 
without crystallizing. This salt is found native in Chili, forming a bed of con- 
siderable thickness. It is generally massive, but forms also six-sided prisms, 
with right summits, which are colourless, and contain 9HO, (Rose.) The 
persulphate of iron is soluble in alcohol. It may be made anhydrous by a 
low red heat ; but after ignition dissolves in water with extreme slowness, 
like calcined alum. 

When hydrated peroxide of iron is digested in the neutral sulphate, a 
red solution is formed, which, according to Maus, is the compound Fe 2 3 , 
2S0 3 . The rusty precipitate which is formed in a solution of the protosul- 
phate from the absorption of oxygen, is another subsulphate, of which the 
empirical formula is S0 3 +2Fe 2 3 . 

A double persulphate of iron and sulphate of potash, or iron alum, is 



394 iron. 

formed by evaporating a solution of the mixed salts to their point of crystal- 
lization. It is colourless and quite analogous in composition to ordinary alum, 
(page 361.) Its formula is KO,S0 3 +Fe 2 3 , 3S0 3 +24HO. 

Another double sulphate is formed, which crystallizes in large six-sided 
tables, and of which the formula is 2(KO,S0 3 )+Fe 2 3 ,2S0 3 4-6HO, (Maus,) 
when potash is added gradually to a concentrated solution of persulphate of 
iron, till the precipitate formed ceases to redissolve, and the solution is eva- 
porated in vacuo. 

Berzelius designates as the ferrosoferric sulphate a combination of the pro- 
to and persulphates of iron, FeO,S0 3 -fFe 2 3 ,3S0 3 . It is the salt produced 
when a solution of the neutral protosulphate of iron is exposed to the air, till 
no more ochre is precipitated. The solution, which is yellowish red, does not 
crystallize, but gives the black oxide of iron when precipitated by an alkali. 
A salt of the same constituents, but in different proportions, forms large sta- 
lactites, composed of little transparent crystals, in the copper mine of Fahlun. 
It is represented by 3FeO,2S0 3 -f 3(Fe 3 3 ,2S0 3 ) + 36HO, (Berzelius.) 

Pernitrate of iron. — By dissolving iron in nitric acid, without heat, as in 
Schosnbein's experiments, (page 386,) a salt is obtained in large, transparent, 
and colourless crystals. From more than one analysis, M. Pelouze found the 
constituents of this salt to be in the proportion of 2Fe 2 3 -f 3N<D 5 +UHO. 
Its solution is decomposed by heat, and the peroxide of iron precipitates. 

Peroxalate of iron is very soluble and does not crystallize. It forms a 
double salt with the oxalate of potash, of a rich green colour, of which the 
formula is 3(KO,C 2 3 ) + Fe 2 3 ,3C 2 3 -f 6HO. The crystals effloresce in 
dry air. In this double salt, the peroxide of iron may be replaced by alumina 
and oxide of chromium (page 363.) This salt is formed by dissolving the 
hydrated peroxide of iron to saturation, in binoxalate of potash, (salt of sorrel,) 
and crystallizes readily from a concentrated solution. The circumstance of 
its being the salt of peroxide of iron most easily obtained and preserved in a 
dry state, should recommend it as a pharmaceutical preparation.* 

The benzoate and succinate of peroxide of iron are insoluble precipitates. 
Hence the benzoate and succinate of ammonia are employed to separate iron 
from manganeses. As both these precipitates are dissolved by acids, the iron 
solution should be made as neutral as possible. The formula of the succinate 
is, Fe 2 3 ,S. 

* [Tartrate of potash and peroxide of iron, KO,Fe 3 O 3 C 8 H 4 O l0 is formed by dissolving 
bitartrate of potash and peroxide of iron in water by a gentle heat, filtering and evapo. 
rating to dryness by means of a water bath. It is an olive brown slightly deliquescent 
powder, soluble in water and alcohol. It does not. afford precipitates with the alkalies or 
their carbonates or with ferracyanide of potassium. Used medicinally and has entirely 
superseded the prototartrate. 

Percitrate of iron is formed by boiling three parts of nitric acid and two of dry hydrated 
peroxide of iron in twelve parts of water until dissolved. The solution is to be filtered 
and evaporated to dryness on a water bath. The moist hydrate dissolves most readily, 
and the amounts obtained by converting three and a half parts of proto into persulphate, 
precipitating by ammonia and washing may be substituted for the two parts of dry 
hydrate. Percitrate of iron is not crystallizabie. It forms a deep garnet-red translucent 
mass, which in scales is transparent; it has no taste, is completely, though slowly •> 
soluble in water and not altered by the action of the air, — BeraL R, B,] 



COBALT. 395 

SECTION III. 

COBALT. 
Eq. 369, or 29.57; Co. 

Cobalt occurs in the mineral kingdom chiefly in combination with arsenic, as 
arsenical cobalt, CoAs ; or with sulphur and arsenic, as gray cobalt ore, CoAs+ 
CoS 2 , but contaminated with iron, nickel and other metals. Its name is that of 
the Kobolds or evil spirits of mines, and was applied to it by the superstitious 
miners of the middle ages, who w T ere often deceived by the favourable appear- 
ance of its ores. These remained without value, till the middle of the sixteenth 
century, when they were first applied to colour glass blue. They are now con- 
sumed in great quantity for the blue colours of porcelain and stoneware. Co- 
balt is likewise found in almost all meteoric stones. 

To obtain metallic cobalt, the native arseniuret is repeatedly roasted, by 
which the greater part of the arsenic is converted into arsenious acid, and car- 
ried off in vapour, while the impure oxide of cobalt, known as zaffre, remains.' 
This is dissolved in hydrochloric acid, and the remaining arsenic precipitated as 
sulphuret by passing a stream of sulphuretted hydrogen through the solution. 
To get rid of the iron present, the last solution, after filtration, is boiled with a 
little nitric acid to peroxidize that metal ; carbonate of potash is added in excess, 
which throws down carbonate of cobalt and peroxide of iron. The precipitate 
is treated with oxalic acid, which forms an insoluble oxalate of cobalt and the so- 
luble peroxalate of irof!. The oxalate of cobalt is dried and decomposed by 
ignition in a covered crucible, when the oxide is reduced by the carbon of the 
acid, which goes off as carbonic acid, while the metallic cobalt remains as a black 
powder. To separate cobalt from nickel, with which it is almost always asso- 
ciated, the mixed oxalates of cobalt and nickel, obtained by the preceding pro- 
cess, are dissolved in ammonia, after which the liquid is diluted and exposed to 
the air in a shallow basin for several days. The ammonia evaporates, and the 
salt of nickel precipitates as a green powder, while the salt of cobalt remains in 
solution. The liquid is then decanted, and if no additional precipitate subsides 
from it in twenty-four hours, it is free from nickel, and may be evaporated to 
dryness. The precipitate of nickel contains a little cobalt. 

Cobalt is a brittle metal, of a reddish gray colour, somewhat more fusible than 
iron, and of the density 8.5131 (Berzelius.) It is generally stated to be mag- 
netic, even when free from iron and nickel, although a minute quantity of arse- 
nic causes it to lose that property. But Mr. Faraday finds pure cobalt not to 
be susceptible of magnetism. Cobalt is less oxidable in the air or by acids than 
iron, dissolving slowly in diluted hydrochloric or sulphuric acid, when heated, 
with effervescence of hydrogen ; but it is readily oxidized by nitric acid. This 
metal forms a protoxide and peroxide, CoO and Co 2 3 , corresponding with the 
oxides of iron, and also a compound oxide, CoO-f Co 2 3 , analogous to the black 
oxide of iron. 

Protoxide of cobalt, CoO, 469 or 37.57. — Prepared by the ignition of the car- 
bonate, this oxide is a powder of an ash gray colour. It is precipitated by an 
alkali, as a hydrate, from its solutions in acids, of a fine blue. Fused with glass, 
the oxide of cobalt colours it blue, even when in minute quantity, no other 
colouring matter having so much intensity. Smalt blue is a pounded potash 
glass containing cobalt. The salts of this oxide have a reddish colour in so- 
lution. They are not precipitated by sulphuretted hydrogen, when they con- 
tain a strong acid, but give a black protosulphuret with an alkaline sulphuret. 



396 COBALT. 

The oxide is precipitated blue by ammonia, and re-dissolved by an excess of that 
alkali. It is precipitated as a pale pink carbonate by alkaline carbonates, which 
is soluble in carbonate of ammonia. The colour of the ammoniacal solutions of 
the salts of cobalt is red, which is of a lively tint when the oxide is pure, but 
becomes of a dull purple and even brown-black when oxide of nickel is present 
in greater or less quantity. 

Oxide of cobalt appears to combine with alkalies and earths, as well as with 
acids. It dissolves in fused potash, and imparts a blue colour to the compound. 
Magnesia with a drop of nitrate of cobalt, when dried and ignited, assumes a 
feeble but characteristic rose tint, by which the presence of that earth in minerals 
containing no metallic oxides nor alumina, is ascertained in blow-pipe experi- 
ments. A compound of oxide of cobalt with alumina is obtained by mixing 
the solution of a salt of cobalt, which must be perfectly free from iron or nickel, 
with a solution of equally pure alum, precipitating the liquor by an alkaline car- 
bonate, washing the precipitate with care, drying and igniting it strongly. It 
forms a beautiful blue pigment, known as cobalt blue, which may be compared 
in purity of tint with ultramarine. A compound of oxide of cobalt with oxide 
of zinc may be prepared in a similar manner, which is a fine green. 

Chloride of cobalt, CoCl, is obtained by dissolving zaffre or the oxide in hy- 
drochloric acid. Its solution is of a pink red, and affords hydrated crystals of 
the same colour ; but when highly concentrated, the solution assumes an intense 
blue colour and then affords blue crystals of chloride of cobalt, which are an- 
hydrous, (Proust.) The red solution is used as a sympathetic ink : charac- 
ters written with it on paper are colourless and invisible, or nearly so, but when 
the paper is warmed by holding it near a fire or against a stove, the writing 
becomes visible and appears of a beautiful blue. By and by, as the salt ab- 
sorbs moisture the colour again disappears, but may be reproduced by the ef- 
fect of heat. If the paper be exposed to too high a temperature, the writing 
becomes black, and does not afterwards disappear. The addition of a salt of 
nickel to the sympathetic ink, gives a green instead of blue. 

The neutral carbonate of cobalt is unknown, oxide of cobalt, like magnesia, 
being thrown down from its solutions, by alkaline carbonates, as a carbonate 
with excess of oxide. The subcarbonate of cobalt is a pale red powder, which 
contains, according to Setterberger, 2 eq. of carbonic acid, 5 eq. of oxide of co- 
balt, and 4 eq. of water. 

Besides the sulphate of cobalt corresponding with green vitriol, another salt 
was crystallized by Mitscherlich between 68° and 86°, containing 6 eq. of 
water, CoO,S0 3 4- 6HO, isomorphous with a corresponding sulphate of magnesia. 
Sulphate of cobalt forms the usual double salts with sulphates of potash and am- 
monia, containing 6HO. 

Phosphate of cobalt, 2CoO, HO,P0 5 , is an insoluble precipitate of a deep 
violet colour. When 2 parts of this phosphate, or one part of the arseniate of 
cobalt, is carefully mixed with 16 parts of alumina and strongly ignited for a 
considerable time, a beautiful blue pigment is obtained, having all the characters 
of ultramarine, which was discovered by Thenard. 

Arseniate of cobalt, CoO,As0 5 4-6HO, exists as a crystalline mineral. It con- 
tains 6HO, according to Bucholz. 

Peroxide of cobalt, Co 2 3 , has not the same importance as the peroxide of 
iron, as it does not combine with acids. It is formed when chlorine is trans- 
mitted through water in which the hydrated protoxide is suspended, or when 
a salt of the protoxide is precipitated by a solution of chloride of lime. In the 
former case, water is decomposed by the chlorine, and hydrochloric acid pro- 
duced, while the oxygen of the water peroxidizes the cobalt: Co 2 2 and HO 
and CI = Co 2 3 and HC1. The peroxide of cobalt is precipitated as a black 
hydrate, containing 2H0. This hydrate, when cautiously heated to 600° or 



NICKEL. 397 

700° yields the black anhydrous oxide. When the peroxide of cobalt is digested 
in hydrochloric acid, chlorine is evolved, and the protochloride formed. Ex- 
posed to a low red heat, the peroxide loses oxygen, and the compound oxide, 
CoO,Co 2 3 , is produced, (Hess.) When the protoxide of cobalt is calcined 
with a borax glass, at a moderate heat it absorbs oxygen, and a black mass is 
obtained, which mixed with magnetic oxide, serves as a black colour in enamel 
painting. A cobaltic acid, Co0 2 , was supposed to be formed by the conjoint 
action of oxygen and ammonia upon the protoxide, but the evidence of its ex- 
istence is insufficient. 

There exists three sulphur ets of cobalt, a protosulphuret, sesquisulphuret, and 
bisulphuret. 

Percyanide or sesquicyamde of cobalt has not been obtained in a separate 
state, but it exists in a class of double cyanides, of which the radical is cobalti- 
cyanogen,Cy 6 Co 2 , analogous to the ferricyanides. The cobalticyanide of potas- 
sium corresponding with the red prussiate of potash, is formed when protoxide of 
cobalt or its carbonate is dissolved in caustic potash, which has been treated with 
an excess of hydrocyanic acid. It is an anhydrous salt, pale yellow and nearly 
colourless when pure, of the same form as the ferricyanide of potassium. Its 
solution does not affect the salts of iron, but forms a rose-coloured precipitate 
with those of the protoxide of cobalt. 

A phozphuret of cobalt, Co 3 P, was obtained by Rose, as a gray powder, on 
passing hydrogen over the subphosphate of cobalt ignited in a porcelain tube. 
It is also produced by the action of phosphuretted hydrogen on the chloride of 
cobalt, and may be looked upon as analogous in composition to the former com- 
pound, H 3 P. 



SECTION IV. 

NICKEL. 

Eq. 369.7 or 29.62 ; Ni. 

This metal resembles iron and cobalt more than any others, and is asso* 
ciated with these metals in meteorites, and in most of the terrestrial minerals 
which contain it. The principal ore of nickel is arsenical nickel, a mineral 
having the colour of metallic copper, to which the German miners, having 
attempted in vain to extract copper from it, gave the name cupfer-nickel, or 
false copper. This mineral was discovered, by Cronstedt of Sweden, in 1751 , 
to contain a particular metal, which he called nickel. Nickel imparts a re- 
markable whiteness to the metallic alloys which contain it, on which account 
it has come of late to be valued in the arts, b'eing added to brass, to form the 
well-known imitations of silver. 

The metal is prepared from the native arseniuret, or from an artificial ar- 
seniuret called speiss, which contains about 54 per cent, of nickel, and has 
been observed by Wohler in octohedrons of a square base, having the com- 
position Ni As. Speiss is a metallic substance which collects at the bottom 
of the crucibles in which smalt or cobalt blue is prepared. In that operation, 
a mixture of quartzy sand, potashes, and the roasted ore of cobalt are fused 
together. The previous roasting never being perfect, a part of the metals 
escape oxidation, and hence when the mixture described is fused, the cobalt, 
which is more oxidable than nickel and copper, reacts upon the oxides of 
these metals, and reduces them while it is itself oxidated: the nickel and cop- 
per concentrate in the speiss, while the smalt contains almost none of them. 
A salt of nickel may be obtained by treating speiss in fine powder with an 
34 



398 OXIDES OF NICKEL. 

equal weight of sulphuric acid, diluted with four or five times its bulk of 
water, and adding gradually an equal weight of nitric acid, which occasions 
the oxidation of both the nickel and arsenic. The green solution thus obtained, 
when cooled and allowed to stand for twenty-four hours, deposites much arseni- 
ous acid, from which it may be separated by filtration. A quantity of carbo- 
nate of potash, equal to half the weight of the speiss, is then added to the 
solution, which is concentrated and set aside to crystallize. The double sul- 
phate of nickel and potash, NiO,S0 3 -fKO,S0 3 -f6HO, forms easily, and may 
be obtained free from arsenic by a second crystallization, (Dr. Thomson.^ 
The perfect separation of small quantities of cobalt and copper, which these 
crystals may still contain, requires additional processes, for which 1 must re- 
fer to Berzelius, (Traite, I, 486.) With the view of obtaining the metal, the 
insoluble oxalate of nickel may be precipitated from the preceding salt by 
oxalate of ammonia, washed, dried, and ignited gently in a covered crucible. 
The oxalic acid reduces the oxide of nickel, and the metal remains in a spongy 
state. It is pyrophoric, like manganese and iron prepared in the same man- 
ner, if the temperature of reduction has been low. To obtain the metal in a 
solid mass, it should be fused in a crucible covered with pounded glass. The 
oxide of nickel is very easily reduced both by carbonic oxide and hydrogen. 

Nickel, when free from cobalt, is silver white, unalterable in air, and highly 
ductile Its density, according to Richter, is 8.279, and after being forged, 
8.666. Nickel is magnetic nearly to the same extent as iron. Magnets 
composed of this metal lose their polarity at 630° (Faraday.) It is somewhat 
more fusible than iron. Nickel forms two oxides corresponding with the 
protoxide and peroxide of iron; but the double compound of the two oxides of 
nickel, corresponding with the black oxide of iron, has not been observed. 

Protoxide of nickel, NiO; 469.7 or 37.62. — May be obtained by the igni- 
tion of the carbonate or nitrate of nickel, or by precipitation from its salts by 
an alkali, as a dark ash-coloured powder, or as a bulky hydrate, of an apple- 
green colour, NiO, HO. Oxide of nickel is very soluble in acids, but not in 
potash or soda. Ammonia dissolves it, and forms an azure blue solution, from 
which oxide of nickel is precipitated by potash, barytes, and strontian, having 
a considerable tendency to combine with salifiable bases. The solutions of 
its salts have all a green colour, much more intense than that of the ferrous 
salts. They are not precipitated by sulphuretted hydrogen when a strong 
acid is present, but afford a black sulphuret with alkaline sulphurets. The 
carbonate of nickel is of a pale green colour, and soluble in carbonate of am- 
monia. 

Peroxide of nickel, Ni 2 3 , is obtained as a black powder, by exposing the 
hydrated protoxide suspended in water to a stream of chlorine gas. It does 
not combine with acids, and in other respects resembles peroxide of cobalt. 

Besides a proto.wlpharet, NiS, a subsulphuret of nickel, Ni 2 S, is formed, 
like that of manganese, by decomposing the ignited sulphate of nickel by hy- 
drogen. A bisulphuret of nickel also exists in combination as a constituent of 
the mineral, nickel-glance, NiS 2 +NiAs. 

Chloride of nickel, NiCl, forms a solution of an emerald green colour, and 
yields by evaporation a hydrated salt of the same colour, which becomes yel- 
low when deprived of its water of crystallization. Chloride of nickel, sublimed 
at a high temperature without access of air, forms golden scales, which dissolve 
with difficulty. 

Sulphate of nickel crystallizes from a strong solution in slender green prisms, 
isomorphous with epsom salt, of which the composition is NiO,S0 3 -f-7HO. At a 
higher temperature, it crystallizes with 6 eq. of water, NiO,S0 3 -f6HO, like the 
magnesia and cobalt salt, and in the same form. M. Mitscherlich has made 
the singular observation, that when the crystals containing 7 eq. of water are 



zinc. 399 

exposed, in a close glass vessel, to a day of sunshine, or kept for some time in 
a temperate place, they change their form, becoming a mass of small crystals. 
of which the form is the regular octohedron. The original crystals become 
opaque from this change, but lose none of their combined water. Sulphate of 
nickel forms the usual double salts with sulphates of potash and ammonia. 

The useful white alloy of nickel, German silver, or packfong, is formed by 
fusing together 100 parts of copper, 60 of zinc, and 40 of nickel. 



SECTION V. 

ZINC. 

Eq. 403.2 or 32.31 ; Zn. 

The principal ores of zinc are calamine, or the carbonate, a pulverulent 
mineral generally of a reddish or flesh colour, and zinc, blende, a massive mine- 
ral of an adamantine lustre, and often black. The oxide, from the carbonate 
or from the calcined sulphuret, is reduced by means of carbonaceous matter. 
This process is conducted in a distillatory apparatus, of a particular form, 
owing to the volatility of the metal. It consists of a crucible, covered above, with 
an iron tube in its bottom, of which the upper open extremity is in the crucible, 
and the other terminates over a vessel of water below the furnace. The gase- 
ous products and vapour of zinc escape by this tube, and the latter is con- 
densed in the water. Zinc may be purified by a second distillation in a porce- 
lain retort, but the first portions of that metal which come over should be re- 
jected, as they generally contain cadmium and arsenic. 

Zinc is a white metal, with a shade of blue, and possessing a bright metallic 
lustre. It is usually brittle, and its fracture exhibits a crystalline structure. 
But zinc, if pure, may be hammered into thin leaves, at the usual temperature; 
and commercial zinc, which is impure and brittle at a low temperature, acquires 
the same malleability between 210° and 300° : it may then be laminated ; and 
the metal is now consumed in the form of sheet zinc for a variety of useful pur- 
poses. At 400° it again becomes brittle, and may be reduced to powder in a 
mortar of that temperature. The density of cast zinc is 6.862, but it may be 
increased by forging to 7.21. Its point of fusion is 773°, (Daniell.) At a red 
heat, zinc rises in vapour, and takes fire in air, burning with a white flame like 
that of phosphorus ; the white oxide produced is carried up mechanically in the 
air, although itself a fixed substance. Laminated zinc is a valuable substance, 
from its little disposition to undergo oxidation. When exposed to air, or 
placed in water, its surface becomes covered with a gray film of suboxide, 
which does not increase ; this film is better calculated to resist both the me- 
chanical and chemical effects of other bodies than the metal itself, arid preserves 
it. Zinc dissolves with facility in dilute hydrochloric, sulphuric and other 
hydrated acids, by substitution for hydrogen. In contact with iron, it protects 
the latter from oxidation in any saline fluid. Zinc forms probably three oxides, 
the suboxide referred to, the protoxide, and a peroxide, when the hydrated pro- 
toxide is acted upon by a solution of peroxide of hydrogen; but of these, the 
first and last have not been studied, and the protoxide is, therefore, the only 
well-known oxide of zinc. 

Protoxide of zinc; ZnO; 503.2 or 40.31. — May be obtained by the combus- 
tion of the metal in a stoneware crucible, as a white powder, or by precipita- 
tion from its salts, by an alkali, as a white hydrate. It is of a yellow colour at a 
high temperature, which disappears on cooling. Oxide of zinc combines 



400 SALTS OF ZINC. 

with acids and forms salts, which are colourless like those of magnesia. It is 
precipitated as a white gelatinous hydrate, by ammmonia, and redissolved by 
an excess of that alkali. It is soluble also in potash and soda, and combines 
with several other basic oxides. Its salts, containing a strong acid in excess, 
are not affected by sulphuretted hydrogen, but give a white hydrated sulphuret 
with an alkaline sulphuret. By the oxidation of zinc in air and water, without 
access of carbonic acid, a hydrate 3ZnQ-f HO, has been obtained in crystalline 
needles, (Mitscherlich.)* 

The native sulphuret of zinc, or zinc blende, ZnS; crystallizes in oetohe- 
drons. Its colour is variable, being sometimes yellow, red, brown or black. 

Chloride of zinc, ZnCl, is produced by the combustion of zinc in chlo- 
rine, and by dissolving the metal in hydrochloric acid. It is fusible at 212°, 
volatile at a red heat, and perhaps the most dilequescent of salts. 

Iodide of zinc, is formed by digesting iodine, zinc and water together, and 
resembles the chloride. 

The neutral carbonate of zinc, forms the ore of zinc, calamine. When 
precipitated by an alkaline carbonate, the salts of zinc, like those of magnesia, 
yield the neutral carbonate in combination with hydrated oxide, (2ZnQ,C0 2 )-f- 
(3ZnO,HO.) The mineral substance, zinc bloom, is of the same composition. 
Precipitated in the cold, the carbonate is ZnO,C0 2 -|-(2ZnO,HO,) but is con- 
taminated by sulphate of soda, (Mitscherlich.) 

Sulphate of zinc, White vitriol, ZnO, S0 3 -f-7HO. — This salt is formed by 
the oxidation of the native sulphuret at a high temperature, or by dissolving 
the metal in dilute sulphuric acid. It crystallizes in colour- 
, Fig. 106. less prismatic crystals, containing 7 eq. of water, of which 
the form is a right rhombic prism. These crystals are so- 
luble in 2i times their weight of water, at the usual tem- 
perature, and fuse in their water of crystallization, when 
heated. It also crystallizes above 86°, with 6 eq. of water, 
in an oblique rhombic prism (Mitscherlich.) Another hy- 
drate is formed and precipitated as a white powder, according 
to Kuhn, containing 2 eq. of water, when a concentrated so- 
lution of sulphate of zinc is mixed with oil of vitriol. The 
sulphate of zinc forms the usual double salt with sulphate of 
potash, ZnO,S0 3 -j-KQ,S0 3 -f 6HO. The double sulphate of zinc and soda 
contains 4 atoms of water, ZnO,S0 3 -fNaO,SQ 3 -f4HO. It is formed by 
a singular decomposition ("page 152.) When a solution of the sulphate is 
mixed with a quantity of alkali less than sufficient for complete precipitation, 
a subsulphate of zinc precipitates, which according to the analyses of several 
chemists, contains 4 eq. of oxide of zinc to 1 eq. of sulphuric acid, besides water. 
A concentrated solution of sulphate of zinc dissolves the preceding subsalt, 
and when saturated contains a compound of 1 eq. of acid and 2 eq. of base, 
according to Schindler,anddoes not crystallize. From this solution Schindler 
obtained the -former insoluble subsalt with two different proportions of water, 
in long crystalline needles, containing 10HQ, by the spontaneous evaporation 
of the solution, and in brilliant crystalline plates, containing 2HO, which 
were deposited on boiling the solution. He also obtained another subsalt, by 
diluting the same solution with a large quantity of water, as a light bulky 
precipitate, which contained 1 eq. of acid, 8 eq. of oxide of zinc, and 2 eq. of 
water. The insoluble matter which precipitates when dry sulphate of zinc 

* [Oxide of zinc is best prepared by precipitating- by carbonate of ammonia and ex- 
posing the precipitate to a red heat to drive off carbonic acid. When a salt of zinc is pre- 
cipitated by a caustic alkali, a subsalt usually falls and is soluble in an excess of the pre- 
cipitant. ' R. B] 




CADMIUM. 401 

combined with 1 eq. of aumonia (page 294,) is thrown into water, is con- 
sidered, by Dr. Kane, a third subsulphate of zinc, containing 1 eq. of acid, ft 
eq. of oxide of zinc, and 10 eq. of water. All these subsulphates afford neu- 
tral sulphate of zinc to water, after being heated to redness, so that whatever 
their constitution may be, when hydrated, it is certainly different from what it 
is in their anhydrous condition. 

Nitrate of zinc, ZnO,N0 5 -f-6HO, is very soluble in water, and moderately 
deliquescent. 

Phosphate of zinc, 2ZnO,HO.P0 5 4-2HO, is obtained in minute silvery 
plates, which are nearly insoluble, on mixing dilute solutions of phosphate of 
soda and sulphate of zinc. 

Silicate of zinc is found as a crystalline mineral, which has received the 
name of the electrical oxide of zinc, because it acquires, like the tourmalin, a 
high degree of electrical polarity when heated. It contains water, and may be 
represented by the formula 2 (3ZnO,Si0 3 )H-3HO. 

The most important alloys of zinc are those with copper, which form the 
varieties of brass. Zinc also combines readily with iron, and is contaminated 
by that metal, when fused in an iron crucible. 



SECTION VI. 

CADMIUM. 

Eq. 696.8 or 55.83; Cd. 

This metal is frequently found in small quantity with zinc, and derives the 
name cadmium, applied to it by Stromeyer, from cadmia fossilis, a denomina- 
tion by which the common ore of zinc was formerly designated. In the pro- 
cess of reducing ores of zinc, the cadmium which they contain comes over 
among the first products of distillation, owing to the great volatility of that 
metal. It may be separated from zinc, in an acid solution, by sulphuretted 
hydrogen, .which throws down cadmium as a yellow sulphuret. This sul- 
phuret dissolves in concentrated hydrochloric acid, affording the chloride of 
cadmium, from which the carbonate may be precipitated by an excess of car- 
bonate of ammonia. Carbonate of cadmium is converted by ignition into the 
oxide, and the latter yields the metal when mixed with one-tenth of its weight 
of pounded coal, and distilled in a glass or porcelain retort, at a low red 
heat. 

Cadmium is a white metal, like tm, very ductile and malleable. It fuses 
considerably under a red heat, and is nearly as volatile as mercury. The den- 
sity of cadmium, cast in a mould, is 8.604, after being hammered, 8.6944. 
Cadmium may be dissolved in the more powerful acids, by substitution for 
hydrogen, with the aid of heat; but nitric acid is its proper solvent 

Oxide of cadmium. CdO; 796.8 or 63.83. — The only known oxide of 
cadmium is obtained by the combustion of the metal, or by the ignition of its 
carbonate, as a powder of an orange colour, or as a white hydrate by precipi- 
tation from its salts by an alkali. Its density, in the anhydrous condition, is 
8.183, (Herapath.) This oxide is soluble in ammonia, but not in its carbonate, 
(differing in the last property from zinc and copper,) nor in the fixed alkalies. 
Its salts are white, and greatly resemble those of zinc. They are precipitated 
of a fine yellow by sulphuretted hydrogen. 

Sulphuret of cadmium is distinguished from sulphuret of arsenic, which it 

34* 



402 COPPER. 

resembles in colour, by being insoluble in potash, and by sustaining a red heat 
•without subliming. 

Chloride and iodide of cadmium are easily crystallized in combination with 
water. 

Sulphate of cadmium forms efflorescent crystals, CdO, S0 3 +4HO; and 
forms a double salt with sulphate of potash: CdO,S0 3 +KO,S0 3 -f-6HO. 

Several definite alloys of cadmium have been formed. At a red heat, 100 
parts of platinum retain 117.3 parts of cadmium, giving a compound Cd 2 Pt: 
100 parts of copper retain at a red heat, 82.2 of cadmium, which approaches 
nearly the proportion of CdCu 2 . Cadmium forms an amalgam with mercury, 
which crystallizes in octohedrons, and consists of 21,74 parts of cadmium, and 
78.26 of mercury, or CdHg 2 . 



SECTION VII. 

COPPER. 

Eq. 395.7 or 31.71; Cu {cuprum.) 

Copper, if not the most abundant, is certainly one of the most generally dif- 
fused of the metals. Its ores are often accompanied by metallic copper, crys- 
tallized in cubes or octohedrons. The richest mines of this country are those 
in Cornwall and Anglesea. The common ore of this metal is copper pyrites, 
a compound of subsulphuret of copper and sesquisulphuret of iron, or a sul- 
phur salt, Cu 2 S~f Fe 2 S 3 , but in which the two sulphurets are also found in 
other proportions, and which often contains an admixture of the bisulphuretof 
iron. Few metallurgic processes require more skill and attention than the ex- 
traction of copper from this ore. The first object of the process is, by roast- 
ing the ore at a high temperature, in contact with siliceous matter, to oxidate and 
convert the iron into a fusible silicate or slag, while the less oxidable copper is 
obtained as the fusible subsulphuret of copper, but still contaminated with a 
considerable quantity of protosulphuret of iron. By alternate oxidation of 
the last product, and reduction by carbonaceous matter in contact with quartzy 
sand, more of the iron and other oxidable substances are separated in the form 
of scoriae, and the same end is afterwards more perfectly attained by directing 
a stong blast of air upon the surface of the melted copper. 

With the exception of titanium, copper is the only metal of a red colour. 
The crystals of native copper, and of that obtained in the humid way by pre- 
cipitation with iron, belong to the regular system ; but the crystals which form 
in the cooling of melted copper were fo^d by Seebeck to be rhomboidal, and 
to have a different place in the thermo-electric series from the other crystals. 
The density of copper when cast is about 8.83, and when laminated or forged 
8.95 (Berzelius.) It is less fusible than silver, but more so than gold, its point 
of fusion being 1996° (Daniell.) It is one of the most highly malleable metals, 
and in tenacity is only inferior to iron. It has much less affinity for oxygen 
than iron, and decomposes water only at a bright red- heat, and to a small ex- 
tent. In damp air, it acquires a green coating of subcarbonate of copper, and 
its oxidation is remarkably promoted by the presence of acids. The weaker 
acids, such as acetic have no effect upon copper, unless with the concurrence 
of the oxygen of the air, when the copper rapidly combines with that oxygen, 
and a salt of the acid is formed. Copper scarcely decomposes the hydrated 
acids, by displacing hydrogen ; for when boiled in hydrochloric acid, it dis- 
engages only the smallest traces of that gas.. But hydrogen does not precipi - 



PROTOXIDE OF COPPER. 403 

tate metallic copper from solution. Copper acts violently on nitric acid, 
occasioning its decomposition, with evolution of nitric oxide, and dissolving as 
a nitrate. 

Suboxide of copper, Red oxide of copper, Cu^O; 891.4 or 71.42. — This 
degree of oxidation is better marked in copper than in any other metal of the 
magnesian class. The suboxide of copper is found native in octohedral 
crystals, and may be prepared artificially by heating to redness, in a covered 
crucible, a mixture of five parts of the black oxide of copper with four parts of 
copper filings. It is a reddish brown powder, which undergoes no change in 
the air. The surface of vessels of polished copper is often converted into sub- 
oxide, or bronzed, to enable them to resist the action of air and moisture: this 
is done by covering them with a paste of peroxide of iron, heating to a certain 
point, and afterwards cleaning them, to remove the oxide of iron ; or otherwise, 
by means of a boiling solution of acetate of copper. 

Dilute acids decompose suboxide of copper, dissolving the protoxide, and 
leaving metallic copper. Undiluted hydrochloric acid dissolves the suboxide, 
without decomposition, or rather forms a corresponding subchloride of copper, 
which is soluble in hydrochloride acid. The hyd rated alkalies precipitate a 
hydrated suboxide from that solution, of a lively yellow colour, which changes 
rapidly in air from absorption of oxygen. 

Suboxide of copper is also formed when copper is placed in a dilute solution 
of ammonia, containing air, and is dissolved by the alkali. If the ammonia has 
been corked up in a bottle with copper for some time, the liquid is colourless ; 
but on pouring it out in a thin stream, it immediately becomes blue, by absorb- 
ing oxygen. The liquid may be again deprived of colour by returning it to 
the bottle, and closing it up, in contact with the metal. 

Compounds have been obtained of suboxide of copper with several acids, par- 
ticularly with sulphurous acid, the sulphite forming a double salt with sulphite 
of potash, Cu 2 0, S0 2 -f 2(KO, SO„,) with hyposulphurous acid, with sulphuric, 
carbonic, and acetic acids. When fused with vitreous matter, the suboxide of 
copper gives a beautiful ruby red glass; but it is difficult to prevent the sub- 
oxide from absorbing oxygen, when the glass becomes green. 

Subsu/phiiret. of copper, Cu 2 S, forms the mineral copper glance, and is also 
a constituent of copper pyrites. It is a powerful sulphur base. Copper filings, 
mixed with half their weight of sulphur, when heated, unite with intense igni- 
tion, and form this subsulphuret. 

Subchloride of copper, Cu 2 Cl, may be prepared by heating copper filings 
with twice their weight of corrosive sublimate. It was obtained by Mitscher- 
lich in tetrahedrons, by dissolving in hydrochloric acid the subchloride of copper 
formed on mixing solutions of protochlorides of copper and tin, and allowing the 
concentrated solution to cool. Subchloride of copper so prepared is white, 
insoluble in water, soluble in hydrochloric acid, but precipitated by dilution. It 
is dissolved by a boiling solution of chloride of potassium, which, if allowed to 
cool in a close vessel, yields large octohedral crystals of a double chloride : 
Cu 2 Cl+2KCl; they are anhydrous. It is remarkable that the forms of this 
double salt, and of both its constituents, all belong to the regular system * 

Subiodide of copper, Cu 2 I, is a white insoluble precipitate, obtained on mix- 
ing a solution of 1 part of sulphate of copper and 2| parts of protosulphate of 
iron, with a solution of iodide of potassium. 

Protoxide of copper, Black oxide of copper, CuO; 495.7 or 39.71.— The 
base of the ordinary salts of copper. It is formed by the oxidation of copper at 
a red heat, but is generally prepared by igniting the nitrate of copper. It is 
black like charcoal, and fuses at a high temperature. This oxide is remarkable 



Mitscherlich in PoggendorfFs Annalen, 49, 401. 1840. 



404 COPPER. 

for the facility with which it is reduced, at a low. red heat, by hydrogen and 
carbon, which it converts into water and carbonic acid. It is that property 
which recommends oxide of copper for the combustion of organic substances, 
in close vessels, by which their ultimate analysis is effected. The protoxide of 
copper precipitates as a blue hydrate, when a solution of sulphate of copper is 
allowed to fall, drop by drop, into solution of potash. This hydrate is decom- 
posed in boiling water, and becomes brown, but is apt to carry down a little of 
its precipitating alkali, of which it is difficult to deprive the brown oxide alto- 
gether by washing. 

The oxide of copper dissolves readily in ammonia, affording a deep azure 
blue solution. But for this experiment a small quantity of acid, or of a salt of 
ammonia, must be present, the solution appearing to be truly that of a subsalt 
of copper in ammonia, and pure ammonia not dissolving equally pure oxide of 
copper. Dr. Kane obtained, on one occasion, an insoluble ammoniacal oxide 
of copper, by precipitating chloride of copper by ammonia, of which the com- 
position was 3CuO-j-2NH 3 -f 6HO. 

Oxide of copper is a powerful base. Its salts are generally blue or green, 
when hydrated, but white when anhydrous. Although neutral in composition, 
they have a strong acid reaction. They are poisonous ; but their effect upon 
the animal system is counteracted in some degree by sugar. Liquid albumen 
forms insoluble compounds with these salts, and is an antidote to their poison- 
ous action. Copper is separated in the metallic state from its salts by zinc, 
iron, lead, and the more oxidable metals, which are dissolved and take the 
place of the former metal. Copper is completely precipitated by sulphuretted 
hydrogen, as a dark brown or black sulphuret, even from acid solutions. The 
ferrocyanide of potassium gives a characteristic brown precipitate with the salts 
of copper. Its salts also impart a green colour to flame. The black oxide of 
copper dissolves by fusion in a vitreous flux, and produces a green glass. 

Thenard obtained a higher oxide of copper, Cu0 2 , by the action of diluted 
peroxide of hydrogen on the hydrated protoxide. 

Chloride of copper, CuCl-b2HO, is obtained by dissolving the black oxide in 
hydrochloric acid. Its solution, when concentrated is green, but the salt forms 
blue prismatic crystals, which contain two atoms of water. It combines with 
chloride of potassium, and more readily with chloride of ammonium, forming 
the double salts, KCl-fCuCH-2HO, and NH 4 Cl-f'CuCl-f 2HO. 

Carbonates of copper. — When a salt of copper is precipitated by an alkaline 
carbonate, a hydrated subcarbonate is produced, containing 2 eq. of oxide of 
copper to 1 eq. carbonic acid. It is a pale blue bulky precipitate, which be- 
comes denser and green when treated with boiling water. It is used as a 
pigment, and known as mineral green. The beautiful native green carbonate 
of copper, malachite, is of the same composition, CuO,C0 2 -r-CuO,HO. The 
finely crystallized blue copper ore is another subcarbonate. It may be repre- 
sented as the neutral hydrated carbonate of copper, in combination with a 
similar carbonate of copper, in which the constitutional water is replaced by 
oxide of copper: 

CCuO, C0 2 -fHO 
£CuO, C0 2 +CuO. 

In the green carbonate, the constitutional water of the neutral carbonate of 
copper is replaced by hydrate of copper. The neutral carbonate of copper 
itself, of which the formula would be CuO,CO„ -f-HO, is unknown. 

Sulphate of copper, Blue vitriol, CuO,S0 3 ,HO + 4HO; 996.9 + 562.5 or 
79.88 + 45. — This salt may be formed by dissolving copper in sulphuric acid 
diluted with half its bulk of water with ebullition, when the metal is oxidated 
with formation of sulphurous acid. But the sulphate of copper is more gene- 



SALTS OF COPPER. 405 

rally prepared, on the large scale, by the roasting and oxidation of sulphuret of 
copper. It forms large rhomboidal crystals of a sapphire blue, containing 5 eq. 
of water, which loose their transparency in dry air : they are soluble in four 
times their weight of cold, and twice their weight of boiling water. Like the 
other soluble salts of copper, the sulphate has an acid reaction; it is used as an 
escharotic. The water in this salt may be reduced to 1 eq. at 212° ; above 400° 
it is anhydrous and white. Although pure sulphate of copper does not crystal- 
lize with 7HO, yet, when mixed with sulphates of magnesia, zinc, nickel, and 
iron, it crystallizes along with these isomorphous salts in the form of sulphate of 
iron. At a strong red heat, it fuses and loses acid. The anhydrous sulphate 
absorbs 2| eq. of ammonia, and forms a light powder of a deep blue colour, 
When ammonia is added to a solution of sulphate of copper, an insoluble sub- 
sulphate is first thrown down, which is redissolved as the addition of ammonia 
is continued, and the usual deep azure blue ammoniacal solution formed. The 
ammoniacal sulphate may be obtained in beautiful indigo-blue crystals, by 
conducting a stream of ammoniacal gas into a saturated hot solution of the 
sulphate: it is CuO,S0 3 HO+2NH 3 (Berzelius.) These crystals lose 1 eq, 
ammonia and 1 eq. water at 390° (Kane,) and are converted into a green 
powder, CuO,S0 3 -f NH,, or (NH 3 CuO)S0 3 (p. 296;) by the cautious appli- 
cation of a heat not exceeding 500°, the whole ammonia may be got rid of, 
and sulphate of copper quite pure remains behind. Sulphate of copper forms 
the usual double salts with sulphate of potash and with sulphate of ammonia. 
A saturated hot solution of the double sulphate of copper and potash allows a 
remarkable double subsalt to precipitate in crystalline grains, KO,S0 3 -f 3,CuO, 
S0 3 )-|-CuO,HO-f 3HO. A corresponding seleniate falls, under the boiling 
point, and always in crystals. The ammoniacal and double salts of sulphate of 
copper may be represented thus: 

Sulphate of copper (blue vitriol) . . . CuO,S0 3 , HO+ 4HO 

Sulphate of copper and potash .... CuO, S0 3 , (KO. S0 3 ) + 6HO 

Hydrated ammoniacal sulphate of copper CuO, S0 3 , HO-f 2NH fl 

Preceding salt dried at 300° . . . . (NH 3 Cu< >,) S0 3 

Rose's ammoniacal sulphate .... CuO, B0 3 + (.\rT,CuO)S0 3 -f 4NH|' 

Do. heated to 350° CuO, S0 3 -f- (NH 3 CuO)S0 3 . 

Several subsulphafes of copper have been formed. A green powder is ob- 
tained by digesting hydrated oxide of copper in a solution of sulphate of cop- 
per, of which the constituents are, according to Berzelius, SO,, 3CuO and 
3HO. The bluish green precipitate which falls when ammonia is added to 
sulphate of capper, or potash added in moderate quantity to the same salt, 
contains, according to Kane's analysis and my own, S0 3 , 4CuO and 4HO. 
By a larger quantity of potash, Dr. Kane precipitated a clear grass-green sub- 
sulphate, containing S0 3 , 8CuO and 12HO. The last subsulphate, loses ex- 
actly half its water at 300°.* 

Nitrate of copper, CuO, N0 5 -f 3HO, is formed by dissolving copper in 
nitric acid. It crystallizes from a strong solution in blue prisms, which con- 
tain 3 atoms of water, or in rhomboidal plates, which contain 6 atoms of water. 
This salt acts upon granulated tin, with nearly as much energy, as hydrated 
nitric acid. A crystallized ammoniacal nitrate of copper, is obtained by con- 
ducting a stream of ammoniacal gas into a saturated solution of nitrate of cop- 
per. It is anhydrous, and contains N0 5 ,CuO and 2NH 3 * (Kane.) T would 
prefer to represent it as a nitrate of cuprammonium-f-1 eq. of ammonia, that 
is, (NH 3 ,CuO)N0 5 +NH 3 . 

* Transactions of the Royal Irish Academy, vol. 19, p. 1; or An. de Ch. et de Ph.t. 72, 
p. 272. 



406 SALTS OF COPPER. 

Subnitrate of copper, HO, N0 5 -f 3CuO, is a green powder, produced by 
the effect of heat upon the neutral nitrate, at any temperature between 150° 
and 600°; or by adding a quantity of alkali to that salt, insufficient for complete 
precipitation. When oxide of copper is drenched with the most concentrated 
nitric. acid (HO, N0 5 ,) it is this subsalt, singular as it may appear, which is 
formed, even when the acid is in great excess; the reason seems to be, that the 
nitrate of water, being deficient in constitutional water, assumes 3 atoms of 
oxide of copper in its place (page 220.) 

Oxalate of copper and potash, is obtained by dissolving oxide of copper in 
binoxalate of potash; it crystallizes with both 2 and 4 atoms of water. 

Acetates of copper. — The neutral acetate, CuO, (C 4 H s 3 )-f HO, is ob- 
tained by dissolving oxide of copper in acetic acid. It forms fine crystals of 
a deep green colour, containing 1 eq. of water, which lose their transparency 
in air, and are soluble in 5 times their weight of boiling water. This salt also 
forms blue crystals from an acid solution, under 40°, which contain 5HO 
(Wohler.) The green salt is found in commerce under the improper name of 
distilled verdigris. Acetates of copper and potash unite in single equivalents, 
and form a double salt in fine blue crystals containing 8HO. Verdigris is a 
subacetate of copper, formed by placing plates of the metal in contact with the 
fermenting marc of the grape, or with cloth dipped in vinegar. The bluer spe- 
cies which consists of minute crystalline plates, is a definite compound of 1 
eq. acetic acid, 2 eq. oxide of copper, and 6 eq. of water, CuO, (C 4 H 3 3 ,) 
CuO + 6HO. The ordinary green species is a mixture of sesqui and tribasic 
acetates of copper, with the preceding bibasic acetate. Water dissolves out 
from verdigris the sesquiacetate, which presents itself on evaporating the solu- 
tion, sometimes as an amorphous mass, and sometimes in crystalline grains of 
a pale blue colour. It consists of 2 eq. of acetic acid, 3 eq. of oxide of cop- 
per and 6 eq. of water; it loses 3 eq. of water at 212°. The tribasic acetate 
is the insoluble residue which remains, after the lixiviation of verdigris. It is 
a clear green powder, which loses nothing at 212°. It contains 2 eq. of acetic 
acid, 6 eq. oxide of copper, and 3 eq. of water. (Berzelius.) 

Acetate of copper also combines with acetate of lime, and with several other 
salts. The double acetate and arsenite of copper, is a crystalline powder of 
a brilliant sea-green colour, which is used as a pigment, under the name of the 
green of Schweinfurth. It is obtained by mixing boiling solutions of equal 
parts of arsenious acid, and the neutral acetate of copper, adding to the mix- 
ture its own volume of cold "water, and leaving the whole at rest for several 
days. It is a highly poisonous substance. From the analysis of Ehrmann 
its formula is CuO, (C 4 H 3 3 ,-f3(CuO, As0 3 .) 

The most important alloys of copper are those with tin and zinc: 
100 parts copper with 10 tin, form bronze and gun metal. 
100 parts copper with 20 to 25 tin, form bell metal. 
100 parts copper with 30 to 35 tin, form speculum metal. 
A little arsenic is generally added to the last alloy, to increase its whiteness. 

The different varieties of brass are prepared, either by fusing together the 
two metals, copper and zinc, or by heating copper under a mixture of charcoal 
and calamine, an operation in which zinc is reduced and its vapour absorbed 
by the copper. Two or three parts of copper to one of zinc form common 
brass; equal parts of copper and zinc, or four of the former and one of the lat- 
ter, give an alloy of a higher colour resembling gold, and on that account 
called similor. 



LEAD. 407 

SECTION VIII. 

LEAD. 
Eq. 1294.5 or 103.73; Pb {plumbum.) 

Lead was one of the earliest known of the metals. A considerable number 
of its compounds are found in nature, but the sulphuret, or galena, is the only- 
one which is important as an ore of lead. The reduction of the metal is ef- 
fected by heating with exposure to air (or roasting) the sulphuret, by which 
much of the sulphur is burned and escapes as sulphurous acid, and a fusible 
mixture of oxide of lead and sulphate of lead is produced. A fresh portion of 
the ore is added, which reacts upon the oxide of lead, the sulphur and oxygen 
forming sulphurous acid, and the lead of both oxide and sulphuret being con- 
sequently reduced. Lime also is added, which decomposes the sulphate of 
lead, and exposes the oxide to be reduced by the fuel or by sulphuret. 

Lead has a bluish gray colour and strong metallic lustre, is very malleable, 
and so soft, when it has not been cooled rapidly, as to produce a metallic streak 
upon paper. Its density is 11.445, and is not increased by hammering. Its 
tenacity is less than that of any other ductile metal. The melting point of lead 
is 612°; on solidifying, this metal shrinks considerably, so that bullets cast into 
a mould are never quite round. Lead, like most other metals, assumes the 
octohedral form on crystallizing. Lead is one of the less oxidable metals, at 
least, when massive; its surface soon tarnishes, and is covered with a gray pel- 
licle, which appears to defend the metal from farther change. Rain or soft 
water cannot be preserved with safety in leaden cisterns, owing to the rapid 
formation of a white hydrated oxide at that line where the metal is exposed to 
both air and water; the oxide formed is soluble in pure water, and highly poi- 
sonous. But a minute trace of any sulphate or chloride in the water, which 
spring and well water usually contain, arrests the corrosion of the lead, by con- 
verting the oxide of lead into an insoluble salt, and prevents the contamination 
of the water, (Dr. Christison's Treatise on Poisons.) Lead is not directly at- 
tacked by hydrochloric and sulphuric acids, at the usual temperature, but they 
favour its union with oxygen from the air. Its best solvent is nitric acid. 
Besides a protoxide PbO, which is a powerful. base, lead forms a suboxide 
Pb 2 0, and a peroxide Pb0 2 which do not combine with acids. 

Suboxide of lead, Pb 2 0, was discovered by Dulong and is best obtained by 
heating the oxalate of lead to redness in a small retort. It is dark gray, almost 
black and pulverulent, and is not affected by metallic mercury. By the ana- 
lysis of Boussingault, it contains 1 eq. of oxygen to 2 eq of lead. The gray pel- 
licle which forms upon lead exposed to the air is, according to Berzelius, the 
same suboxide. 

Protoxide of lead, PbO, 1394.5 or 111.73. — When a stream of air is thrown 
upon the surface of melted lead, the metal is rapidly converted into the protox- 
ide, of a sulphur-yellow colour. The oxidated skimmings of the metal are, in 
this condition, termed massicot, and were at one time used as a yellow pigment 
This preparation is fused at a bright red heat, and the oxide is thus separated 
from some metallic lead, with which it is intermixed in massicot. The fused ox- 
ides forms a brick red mass, on solidifying, which divides easily into crystalline 
scales, which are tough and not easily pulverized ; they form litharge. • The 
protoxide of lead can be obtained distinctly crystallized by various processes, 
but always presents itself in the same form, an octohedron with a rhombic base 



408 PROTOXIDE OF LEAD. 

(Mitscherlich.) By igniting the subnitrate of lead, the protoxide is obtained 
very pure and of a rich lemon yellow colour. Its density when fused is 
9.4214. 

When the acetate, or any other salt of lead, is precipitated by potash, the pro- 
toxide falls as a white hydrate, which may be dried at 212° without decom- 
position. It contains 3\ per cent, water, and is, therefore, the hydrate 2PbO-f 
HO, (Mitscherlich. ) Oxide of lead likewise crystallizes anhydrous, from solution, 
at the usual temperature, when water to combine with is denied to it, in the 
circumstances of its precipitation. This oxide dissolves in above 12,000 times 
its weight of distilled water, which acquires thereby an alkaline reaction ; but 
not in water containing any saline matter. It is soluble in potash or soda ; and 
the solutions, when evaporated afford small crystals of an alkaline compound. 
A compound of lime and oxide of lead is obtained in needles, when hydrate of 
lime and that oxide are heated together, and the solution allowed to evaporate 
with exclusion of air. This solution has been employed to dye the hair black. 
The oxide of lead combines readily with the earths and metallic oxides by fusion, 
and when added to the materials of glass imparts brilliancy to it and increased 
fusibility. 

Oxide of lead is a powerful base, resembling barytes and strontian, and affords 
a class of salts which often agree in form and in general properties with the salts of 
these earths. Its carbonate occurs in plumb ocalci/e, in the form of carbonate 
of lime ; and isomorphism by which the protoxide of lead is connected with the 
magnesian oxides. All its soluble salts are poisonous, although no salt of lead, 
with the exception of the carbonate, which is insoluble, is highly so (Dr. A. T. 
Thomson.) Lead is precipitated by sulphuretted hydrogen, as a black sulphuret, 
even from acid solutions. Neutral salts of lead are also precipitated by so- 
lutions of carbonates, chlorides, sulphates, phosphates, etc., the corresponding 
salts of lead being insoluble. Iodide of potassium and red chromate of potash 
produce yellow precipitates in salts of lead, which are highly characteristic of 
the metal. Iron and zinc throw down metallic lead. If a mass of zinc be sus- 
pended in a solution, made by dissolving one ounce of acetate of lead in two 
pounds of distilled water, the lead is precipitated in beautiful crystalline plates, 
which are deposited only in metallic contact with the zinc, but extend from ' 
it to a considerable distance in the liquid, forming what is called the lead tree. 

Peroxide of lead, Pb0 2 , may be obtained in the same manner as the perox- 
ides of cobalt and nickel, exposing the protoxide suspended in water to a stream 
of chlorine ; also by fusing protoxide of lead with chlorate of potash at a tem- 
perature short of redness ; or by digesting the following intermediate oxide, 
minium, in diluted nitric acid, which dissolves protoxide of lead, decanting off 
the nitrate of lead, and washing the powder which remains with boiling water. 
Peroxide of lead is of a dark earthy brown colour. It loses half its oxygen by 
ignition, absorbs sulphurous acid with great avidity and becomes sulphate of 
lead, affords chlorine when digested in hydrochloric acid, and the nitrate of pro- 
toxide of lead with water, when digested in ammonia. 

Minium, or Red lead is formed by heating massicot or protoxide of lead, 
which has not been fused, to incipient redness in a flat furnace, of a particular 
construction, and directing a current of air upon its surface. Oxygen is ab- 
sorbed and an oxide formed of a fine red colour, with a shade of yellow. It is 
not constant in composition. The proportion of oxygen, when the absorption 
is least considerable, approaches that of a compound 3PbO+Pb0 2 , and such 
was the composition of a crystallized compound of a fine red colour, formed by 
accident in a minium furnace, and analyzed by Houton-Labillardiere. But 
when the absorption is favoured by time and most considerable, it approaches, 
but never exceeds 2.4 per cent, of the original weight of the protoxide, which 
gives a compound of 2Pb0-f-Pb0 2 , according to the observations of M. Dumas. 



SULPHURET OF LEAD. 409 

The proportion of 3 eq. of metal to 4 eq. of oxygen, which minium thus posesses, 
is a very common one, but generally due to the combination of a protoxide 
with a peroxide, the latter containing 2 atoms of metal and S atoms of oxygen, 
as the peroxide of iron. Berzelius considers the composition of minium to favour 
the existence of such an oxide of lead Pb 2 3 ; minium would be represented as 
PbO+Pb 2 3 . The finest minium is obtained by calcining oxide of lead from 
the carbonate, at about 600°. 

Minium is not altered by being heated in a solution of acetate of lead, which 
is capable of dissolving free protoxide of lead. When heated to redness it 
losses oxygen, and the protoxide remains. It does not combine with acids, 
but is resolved by a strong acid into peroxide of lead, and protoxide, the last 
combining with the acid. When minium is treated with concentrated acetic 
acid, it first becomes white, then dissolves entirely in a new quantity of acid 
without colouring it. But the solution gradually decomposes, and peroxide of 
lead separates from it of a blackish brown colour. (Berzelius.) 

Proto sulphur et of lead, PbS, is thrown down from salts of lead as a black 
precipitate, by sulphuretted hydrogen, which is insoluble in diluted acids or in 
alkalies. It forms also the ore galena, which crystallizes in the cube and other 
forms of the regular system; its density is 7.585. Sulphuret of lead is de- 
composed easily by nitric acid, and converted into nitrate and sulphate of lead, 
with the separation of a little sulphur. Concentrated and boiling hydrochloric 
acid dissolves it, with disengagement of sulphuretted hydrogen gas. Galena 
can be united by fusion with more lead, and gives the subsulphurets Pb 4 S. 
and Pb. 2 S. When a solution of persulphuret of potassium is added to a salt 
of lead, a blood red precipitate appears, which is a persulphuret of lead, but 
is almost immediately changed into the black protosulphuret of lead and free 
sulphur. 

Chloride of 'lead, PbCl, 1737.15 or 139.2.— Lead dissolves slowly in hy- 
drochloric acid, by substitution for hydrogen, forming the chloride of lead. 
The same compound is obtained by digesting oxide of lead in hydrochloric 
acid, and also falls as a white precipitate, when a salt of lead is added to any 
soluble chloride. The chloride of lead is soluble in 135 times its weight of 
cold water, and more so in hot water, from which it crystallizes in cooling in 
long flattened acicular crystals, which are anhydrous. The chloride of lead 
is very fusible, and may be sublimed at a high temperature. It combines in 
several proportions with oxide of lead. The bibasic chloride of lead, PbCl 
-f 2PbO, is a colourless crystalline mineral, found at Mendip in Somersetshire. 
The tribasic chloride of lead, PbCl f 3PbO-f 4HO, is a white insoluble powder 
that falls when ammonia is added to a solution of chloride of lead. It contains 
7 per cent, of water (Berzelius.) A surbasic chloride of lead, PbCl-f 7PbO, 
is produced on fusing by heat a mixture of 10 parts of pure oxide of lead, and 
1 part of pure sal-ammoniac, a portion of the lead being at the same time re- 
duced. The surbasic chloride fused affords cubic crystals, on cooling slowly. 
It forms in that state a beautiful yellow pigment, known as Turner's yellow in 
this country, and Cassel yellow in Germany. It was prepared in England by 
digesting litharge, with half its weight of common salt, a portion of which is 
converted into caustic soda, and afterwards washing and fusing the oxichloride 
formed. But it is sufficient to use 1 part of salt to 7 parts of oxide of lead in 
this decomposition. 

Iodide of lead, Pbl, 2874 or 230.3. — Appears as a beautiful lemon yellow 
powder, when iodide of potassium is added to a salt of lead. It is soluble in 
194 parts of boiling water, and in 1235 parts of water at the usual tempera- 
ture, and may be obtained from solution in brilliant hexagonal scales of a 
golden yellow colour. A compound of a paler yellow, which appears in di- 
lute solutions, and when the salt of lead is in excess, is a basic iodide. M 
35 



410 LEAD. 

Denot finds three basic iodides of lead, containing to 1 eq. of iodide of lead, 1 
eq., 2 eq. and 5 eq. of oxide of lead, and always 1 eq. of water, which last 
they do not lose below a temperature of about 400°. 

Cyanide of lead, PbCy, is a white insoluble powder, obtained by precipita- 
tion. 

Carbonate of lead, Ceruse, White lead; PbO, C0 2 ; 1670.9 or 133.89.— 
Occurs in nature well crystallized, in the form of carbonate of barytes. It is 
precipitated as a white powder, of which the grains although very minute are 
crystalline, when an alkaline carbonate is added to the acetate or nitrate of lead. 
The precipitate is anhydrous. When oxide of lead is left covered with water 
in an open vessel, it absorbs carbonic acid, and becomes white, forming the 
subcarbonate PbO, C0 2 -fPbO, HO. 

The carbonate of lead is invaluable as a white pigment from its great opa- 
city, which gives it that property, called body by painters, and enables it to 
cover well. As precipitated by an alkaline carbonate, it is deficient in body, 
owing to the transparency of the crystalline grains composing the precipi- 
tate. It is also a neutral carbonate, as thus prepared, and differs in com- 
position from the ceruse of commerce, which Mulder finds always to contain 
hydrated oxide of lead in combination with the carbonate of lead. The re- 
sult of Mulder's analyses of numerous specimens of white lead, is, that there 
are three varieties of that substance, the composition of which is expressed by. 
the three following formulae: 

2(PbO, C0 2 )+PbO, HO; 

5(PbO, GO;)+2(PbO, HO;) and 
3(PbO, CO;)+PbO, HO. 

Mr. T. Richardson, who has also been engaged with a chemical examination 
of the varieties of white lead, finds all of them to contain a portion of oxide of 
lead, in addition to the carbonate, and so far confirms the conclusions of Mul- 
der.* 

In the old or Dutch mode of preparing white lead, which is still extensively 
practised, thin sheets of the metal are placed over gallipots containing weak 
acetic acid (water with about 2i per cent, dry acid,) themselves imbedded in 
fermenting tan, of which the temperature varies from 140° to 150°. The 
action is often very rapid, and the metal disappears in a few weeks to the 
centre of the sheet. In this process from two to two and a half tons of lead 
(4480 to 5600 pounds) are converted into carbonate, by a quantity of vinegar 
•which does not contain more than the small quantity of 50 pounds of dry acetic 
acid. Hence the metal is certainly neither oxidized nor carbonated in this 
process, at the expense of the acetic acid. The oxygen must be derived from 
the air, and the carbonic acid from the fermenting tan. In the newer process, 

* The following are Mr. Richardson's results, which he has communicated to me. The 
specimens were all dried at a temperature of about 300° for 24 hours, previous to analysis. 
No. 1, was made by the French Plan, (by transmitting carbonic acid through subacetate 
of lead;) No. 2 is Kremner white, Nos. 3, 4, 5, were made by causing small pieces of lead 
to be agitated in a tub, into which carbonic acid was passed, as practised in London; Nos. 
6, 7, 8, 9, 10, were made by the old Dutch plan, but each of the specimens was from a dif. 
ferent manufacturer ; 

1 234 5 67 8910 

Carbonic Acid. 13.70 15.83 13.70 13.03 13.24 14.61 13.71 13.99 12.99 14.95 
Protox. Lead. 86.00 83.49 85.66 8598 86.46 84.83 86.02 86.09 86.45 85.02 

99.70 99.32 99.36 99.01 99.70 99.44 99.73 109.08 99.44 99.97 
While the neutral carbonate of lead consists in 100 parts of 
Carbonic acid. . . . 16.54 
Oxide of lead. , . . 83.46 

• t ~ 
100.00 



SALTS OF LEAD. 411 

litharge, without any preparation, is mixed with water and about 1 per cent, 
of acetate of lead, and carbonic acid gas sent over it; the oxide of lead is rapidly- 
converted into excellent ceruse. There can be little doubt that all the oxide 
of lead is successively dissolved by the acetate, and presented to the carbonic 
acid as a soluble subacetate; a compound which it is known, absorbs carbonic 
acid with the greatest avidity, and allows its excess of oxide to precipitate as 
carbonate of lead. The new process supplies likewise the theory of the old 
one, the function of the acetic acid being manifestly the same in both processes. 
Nitrate of lead has been substituted for the acetate, with other things the same 
as in the last process. 

Sulphate of lead; PbO,S0 3 ; 1895.66 or. 151.90.— This salt falls when sul- 
phuric acid or a soluble sulphate is added to a solution of acetate or nitrate of 
lead, as a white dense insoluble precipitate, which appears by the microscope 
to be composed of minute crystrals. Sulphate of lead contains in 100 parts, 
26.44 sulphuric acid and 73.56 oxide of lead, and may be exposed to a red 
heat without decomposition. Mr. Richardson finds that this salt acquires 
considerable opacity, and may be substituted for ceruse, when prepared 
in a mode analogous to the new process for that substance; namely by supply- 
ing sulphuric acid, in a gradual manner, to a thick mixture of litharge and 
water, containing a small proportion of acetate of lead. The sulphate of lead 
may be obtained thus, having any desirable excess of oxide of lead. 

Nitrate of lead; PbO,N0 5 ; 2071-53 or 165. 99. —Is obtained by dissolving 
litharge, at the boiling point, in slightly diluted nitric acid, which should be 
free from hydrochloric and sulphuric acids. The neutral nitrate crystallizes 
in large octohedrons, with the secondary faces of the cube, which are some- 
times transparent, although generally white and opaque. The crystals are 
anhydrous; they are soluble in lh times their weight of cold, and in much less 
hot water. The nitrate of lead is decomposed by an incipient red heat, yield- 
ing, with oxygen gas, the peroxide of nitrogen, which is prepared in this way, 
and leaving the yellow oxide of lead. When a small quantity of ammonia is 
added to nitrate of lead, or when a dilute solution of the neutral salt is boiled 
with oxide of lead in fine powder, a soluble bibasic nitrate of lead is formed 
Pb0,N0 s 4Pb0. It crystallizes during evaporation in fine scales, or in 
little opaque grains, which are anhydrous. The granular crystals decrepitate 
when heated, with extraordinary force. The tribasic nitrate of lead precipi- 
tates, when ammonia is added in very slight excess to a solution of nitrate 
of lead. Its constituents are 2N0 5 ,6PbO and 3HO (Berzelius.) It is 
a white powder, which is soluble to a small extent in pure water. When 
nitrate of lead is digested with a considerable excess of ammonia, the decom- 
position stops at the point at which 6 eq. of oxide of lead are combined with 
1 eq. of nitric acid. The sexbasic nitrate of lead contains 2N0 5 ,12PbO and 
3HO. (Berzelius.) 

Nitrites of lead. — When a solution of 100 parts of nitrate of lead is boiled 
with 78 parts of metallic lead in thin turnings, the lead is dissolved, and a little 
nitric oxide is evolved, the last being the result of a partial decomposition of 
nitrous acid previously formed. The solution is alkaline and yellow; and 
gives, on cooling, brilliant crystalline plates of a golden yellow colour, which 
are the bibasic nitrite of lead, 2PbO-fN0 3 . By dissolving 100 parts of this 
salt in water at 167° (75° cent.,) and then mixing with the solution 35 parts of 
oil of vitriol, previously diluted with four times its weight of water, one half of 
the oxide of lead is precipitated as sulphate of lead, and a solution is obtained 
of a deep yellow colour, from which the neutral nitrite of lead, PbO, N0 3 -f- 
HO, crystallizes. This salt gives yellow crystals, resembling the nitrate in 
form. Its solution absorbs oxygen from the air, and like all the nitrites, gives 
off nitric oxide at 176° (80° cent.,) and a subnitrate of lead precipitates. Ber- 



412 LEAD. 

zelius, to whom we are indebted for the preceding facts, also formed a quadri- 
basic nitrite of lead, containing N0 3 ,4PbO and HO. 

Acetate of. lead, PbO, (C 4 H 3 3 ) + 3HO.— This salt is met 
Fig. 106'. with well crystallized, and in a state of great purity in com- 
merce. It is generally prepared by dissolving litharge in the 
acetic acid procured by the distillation of wood. It crystal- 
lizes in flattened four-sided prisms, has a taste which is first 
sweet and then astringent, is very soluble in water, 100 parts 
of water dissolving 59 of the salt at 60°, and soluble in 8 parts 
of alcohol. It effloresces in air, and is apt to be decomposed 
in part by the carbonic acid of the air, and thus to become 
partially insoluble. It loses the whole of its water when dried 
at the usual temperature in vacuo. M. Payen crystallized the 
anhydrous acetate, from solution in absolute alcohol. 

Tribasic subacetate of lead, PbO, (C 4 H 3 3 )-f 2PbO, is formed by digesting 
oxide of lead in a solution of the neutral salt, till it is strongly alkaline. This salt 
does not crystallize when so prepared, but may be dried, and then contains no 
water. It is very soluble, but must be dissolved in distilled water, as the car- 
bonic, hydrochloric and other acids, in welkwater, precipitate its oxide of lead. 
M. Payen has observed that the tribasic subacetate crystallizes readily, in fine 
prismatic needles, when formed by adding ammonia to a moderately strong 
solution of the neutral acetate. The crystals contain 1 eq. of water, which they 
lose at 212° The acetate of ammonia formed at the same time, appears to 
give stability to the subacetate of lead in solution, and prevents an excess of a 
whole equivalent of ammonia from throwing down any oxide of lead from the 
solution. This am.moniacal solution of the subacetate of lead, prepared without 
an excess of ammonia, is a convenient form in which to apply that salt as a re- 
agent* 

Sesquibasic acetate of had, 3PbO,2(C 4 H 3 3 )+HO.— Was obtained by 
Payen by adding 3 eq. of the neutral acetate, to a concentrated and boiling 
solution of 1 eq. of the tribasic nitrate. It is also produced when the neutral 
and anhydrous acetate of lead is heated in a retort or porcelain capsule, till the 
whole, after being liquid, becomes a white and porous mass. The sesquibasic 
acetate is then formed by the decomposition of 3 atoms of neutral acetate of 
lead, from which there separate the elements of 1 atom of acetic acid, in the 
form of carbonic acid and acetone, (Matteucci, WOhler.) This basic salt is 
very soluble, and crystallizes in plates of a pearly lustre. 

A sexbasic acetate of lead, 6PbO, (C 4 H 3 3 ,) is formed on dropping a solu- 
tion of the neutral, or of tribasic acetate of lead, into ammonia in excess. It is 
a white precipitate, which examined by the microscope, has a crystalline aspect. 
It contains a little water, which it loses when dried in vacuo. 

Alloys of lead. — Lead and tin may be fused together in all proportions. 
M. Rudberg finds that these metals combine. in certain definite proportions 
having fixed points of congelation : 



ALLOYS OF LEAD AND TIN. 

1 atom of lead and 3 atoms of tin, congeal at 368.6°. 

1 atom of lead and 1 atom of tin, at 464°. 

2 atoms of lead and 1 atom of tin, at 518°. 

3 atoms of lead and 1 atom of tin, at 536°. 

* Memoire sur les Acetates et le Protoxide de Plomb, par M. Payen, An. de Chim. et 
de Phys. t. 66, p, 3J. 



BISMUTH. 413 

A thermometer place.d in a fluid alloy of 1 atom of lead and 2 atoms of tin, 
becomes stationary when the temperature falls to 392°, a portion solidifies, and 
a more fusible alloy separates ; the temperature again falls, and afterwards 
becomes stationary at 368.6°, the crystallizing point of the alloy composed of 1 
atom of lead, and 3 atoms of tin. If the alloy contains so much tin that its 
point of complete congelation is under 368°. 6, the last compound always sepa- 
rates from it, at that point, and the thermometer remains stationary for a time, 
whatever may be the proportion of the metals in the alloy * Fine solder is an 
alloy of 2 parts of tin and 1 of lead ; it fuses at about 360°, and is much em- 
ployed in tinning copper. Coarse solder contains one-fourth of tin, and fuses 
about 500° ; it is the substance employed for soldering by plumbers. 

Lead, as reduced from the native sulphuret, always contains a little silver. 
The latter is separated by allowing two or three tons of the melted metal to 
cool slowly in a hemispherical iron pot ; when the lead, as it solidifies, separates 
in crystals, which can be raked out. The silver remains almost wholly in the 
more fusible portion, or wmat may be looked upon as the mother-liquor of these 
crystals; so that by this operation the argentiferous alloy is greatly concen- 
trated. This mode of separation was discovered by Mr. Pattinson, of New- 
castle. To separate the remaining lead, much of it is converted into massicot, 
by the action of air upon its surface, in the shallow furnace used for that pre- 
paration ; and the last portions of lead are removed by continuing the oxidation 
upon a porous basin or cupel of bone-earth, which imbibes the fused oxide of 
lead, while the melted silver is found in a state of purity upon the surface of the 
cupel, not being oxidable at a high temperature. 



SECTION XI. 

BISMUTH. 

Eq. 886.9 or 71.07; Bi. 

Bismuth generally occurs in the metallic state, and is separated from the 
gangue or accompanying rock by fusion. It may be prepared in a state of 
purity, for chemical purposes, by reducing, with charcoal, the oxide of bismuth 
obtained by igniting the subnitrate. 

Bismuth is a white metal of a reddish shade, and highly crystallizable. Its 
density is 9.53, which may be increased by cautious hammering to 9.8827. It 
is more fusible than lead, melting at 497°, according to Crichton, and at 507°, 
according to Rudberg. This metal, like water, expands considerably in crys- 
tallizing. It is volatile at a full red heat, and burns in air at a high temperature 
with a pale blue flame, and the formation of copious fumes of oxide of bismuth. 
This metal does not oxidate in air ; it dissolves with difficulty in boiling hydro- 
chloric or diluted sulphuric acid, by substitution for hydrogen, but is readily 
oxidized and dissolved by nitric acid. Bismuth resembles several of the mag- 
nesian metals, in forming, besides a protoxide, a suboxide of which the compo- 
sition is unknown, and a peroxide Bi0 2 , which does not combine with acids. 

Suboxide of bismuth is formed when the subnitrate is digested in a solution 
of •protochloride of tin, and appears as a black powder, which is soluble with 
heat in hydrochloric acid, (Vogel.) When bismuth is oxidated and fused with 
metaphosphate of soda upon charcoal, by the blow-pipe, and the bead after. 

* Rudberg, An de Chim. et de Phys. t. 48, p. 363. 
35* 



414 BISMUTH. 

wards held in the reducing flame, a colourless glass is obtained, which assumes 
a black colour on cooling. This is analogous to what happens with suboxide 
of copper, and appears to indicate that suboxide of bismuth forms salts, at least 
in the dry way. 

Protoxide of bismuth, BiO; 986.9 or 79.07; BiO. — Is obtained by the com- 
bustion of bismuth, as a straw yellow powder, or by the ignition of the sub- 
nitrate. The density of the fused oxide is 8.211. It combines with acids, 
and forms white salts. 

Sulphuret of bismuth, BiS, occurs crystallized, and has, according to Mr. 
W. Phillips, a form similar to sulphuret of antimony. Hence M. RegnauU 
is disposed to class bismuth with antimony, (An. de Ch. &c. t. 73, p. 70.) 
The eq. of bismuth would then be multiplied by 3, or made 2660.7, and the 
protoxide be represented by Bi0 3 . Its density is 7.501. The sulphuret is 
dissolved by the metal- in all proportions, by fusion, but separates again when 
the latter congeals (Lagerhjelm.) 

Chloride of bismuth, and sulphate of the oxide of bismuth, are formed, 
by dissolving oxide of bismuth in concentrated hydrochloric and sulphuric 
acids. Thev both afford subsalts, when decomposed by water, namely Bi- 
Cl+£BiO-f*HO (Phillips,) and 3BiO+S0 3 (Berzelius.) The former is 
known as pearl white. An insoluble sub carbonate of bismuth precipitates, 
on throwing the nitrate into the solution of an alkaline carbonate, which is 
used in medicine; also a crystalline tartrate of bismuth, on adding the nitrate 
to a solution of Rochelle salt. 

Nitrate of bismuth; BiO,N0 5 + 3HO; 1664-f337.5-.or 133.33+27,— -This 
salt is produced when bismuth in powder is thrown into nitric acid, of density 
1.42: the action is very violent. Crystals are formed on cooling, which cor- 
respond in composition with the magnesian nitrates. This salt is decomposed 
by heat in the same way as the nitrate of copper, but at a lower temperature, 
beginning to lose acid in dry air at 80°. Three atoms of the hydrated salt 
are resolved by heat into 2 atoms of hydrated nitrate of water (acid of sp. gr. 
1.42,) and 1 atom of subnitrate of bismuth: 3(BiO,N0 5 -f 3HO)=2(HO, 
N0 5 +3HO,) and HO,N0 5 +3BiO. The neutral nitrate, and ail the solu- 
ble salts of bismuth are decomposed by water, which combines with the acid 
and throws down the oxide, generally in combination with a portion of the 
acid. Oxide of bismuth must, therefore, be considered as inferior to water, 
in basic power. The nitrate of bismuth is highly corrosive; it is precipitated 
as a black sulphuret by sulphuretted hydrogen. 

Subnitrate of bismuth, HO,N0 5 +3BiO, mentioned above, is produced 
at a temperature so low as 180°, and maybe exposed to a temperature of 500° 
without decomposition., At a higher temperature its acid and water go off 
together. It is the oniy subnitrate of bismuth ever produced, in the decom- 
position of the neutral nitrate by heat. When crystals of the- neutral nitrate 
are decomposed by 24 times their weight of water, they give, according to M. 
Duflos, a hydrated subnitrate containing N0 5 ,4BiO and 3HO. This subni-. 
trate, which is used in pharmacy and known as the magistery of bismuth, is 
a brilliant white powder of pearly lustre, composed of microscopic crystalline 
grains; which is light after being dried, like- magnesia alba. When prepared 
by pouring the solution- of the neutral nitrate, drop by drop, into a large quan- 
tity of water, the composition of the subnitrate is 3BiO + N9 5 , according to 
Mr. Phillips. The subnitrate of bismuth is employed as a cosmetic; it is also 
used as an internal remedy. 

Peroxide of bismuth, BiO,, was formed by Stromeyer by boiling anhy- 
drous protoxide of bismuth finely levigated, with chloride- of soda. It is a 
dark brown anhydrous powder, which gives chlorine with hydrochloric acid, 
but is not reduced to the state of protoxide by sulphurous acid. 



TIN. 415 

The alloys of bismuth are remarkable for their fusibility. The amalgam 
of this metal is highly liquid. An alloy of 8, parts bismuth, 5 lead and 3 tin 
melts at 202°; another mixture of 2 bismuth, 1 lead and 1 tin at 200°.75, these 
mixtures are known as fusible metal. Bismuth is also added to the alloy of 
tin and lead used for casting stereotype plates. Besides increased fusibility, 
bismuth communicates to this alloy the property of expanding on becoming 
solid, by which it is calculated to take an accurate impression* 



ORDER V. 



OTHER METALS PROPER HAVING ISOMORPHOUS RELATIONS WITH 
THE MAGNESI AN FAMILY. 



SECTION I. 
TIN. 

Eq. 735,3 or 58.92; Sn (stannum.) 

Tin does not occur native, but its common ore is reduced by a simple pro- 
cess, and mankind appear to have been in possession of this metal from the 
earliest ages. The most productive mines of tin are those of Cornwall, from 
which, the ancients appear to have derived their principal supply of this metal, 
and those of the peninsula of Malacca and island of Banca in India. 

The only important ore of tin is the peroxide, which is found in Cornwall, 
both in veins traversing the primary rocks, and in alluvial deposites in their 
neighbourhood. In the latter case the ore presents itself in rounded grains of 
greater or less size, which form together abed covered by clay and gravel. 
The ore has evidently been removed from its original situation, and the grains 
rounded by the action of water, which has at the same time divested it of the 
other metallic ores with which it is accompanied in the vein; these being softer 
are more easily reduced to powder, and have been carried away by the stream. 
This ore, called stream tin, is easily reduced by coal, and gives the purest 
tin. The metal from the ore of the veins, is contaminated with iron, copper, 
arsenic and antimony, from which a portion of it is partially purified by liqua- 
tion. Bars of the impure metal are exposed to a moderate heat, by which 
the pure tin is first melted, and separates from a less fusible alloy, containing 
the foreign metals. The purer portion is called grain tin, and the other ordi- 
nary tin or block tin. The mass of grain tin is heated till it becomes brittle, 
and then let fall from a height. By this, it splits into irregular prisms, some- 
what, resembling basaltic columns. This splitting is. a mark of the purity of 
the tin, for it does not happen when the tin is impure. 

Pure tin is silver white, very soft, and so malleable, that it may be beaten 
into thin leaves, tinfoil not being more than l-1000dth of an inch in thickness. 
When a bar of tin is bent, it emits a grating sound, which is characteristic; 



416 PROTOXIDE OF TIN. 

and when bent backwards and forwards rapidly, several times in succession, 
becomes so hot that it cannot be held in the hand. At the temperature of 
boiling water, tin can be drawn out into wire, which is very soft and flexible, 
but deficient in tenacity. The density of pure tin is 7.285, or 7.293 after be- 
ing laminated; that of the tin of commerce is said to vary from 7.56 to 7.6. 
Its point of fusion is 442°, both by Crichton and Rudberg; 445°. 6 by Kupffer. 
Tin is volatile at a very high temperature. The brilliancy of the surface of 
tin is but slowly impaired by exposure to air, and even in water it is scarcely- 
acted upon. Hence the great value of this metal for culinary vessels, and for 
covering the more oxidable metals, such as iron and copper, when employed 
as such. Of tin three oxides are known, the protoxide SnO, deutoxide 
Sn 2 3 , and peroxide Sn0 2 . 

Protoxide of tin, Stannous oxide; SnO, 835.3 or 66.92. Tin dissolves 
in undiluted hydrochloric acid, at the boiling temperature, by substitution for 
hydrogen, and forms the protochloride of tin. From this the protoxide is 
precipitated by an alkaline carbonate, as a white hydrate, which may be 
washed with tepid water and dried at a temperature not exceeding 176°. It 
does not contain a trace of carbonic acid. This white powder dried more 
strongly, in a retort filled with carbonic acid, and heated to redness, gives the 
anhydrous oxide, as a black powder, of which the density is 6.666. In this 
state the oxide is permanent, but if a body at a red heat is brought in contact 
with it in open air, it takes fire and burns, and is converted entirely into per- 
oxide. The protoxide of tin dissolves in acids, and with more facility when 
hydrated than after being ignited. This oxide is also dissolved by potash and 
soda, but' the solution after a time undergoes decomposition; metallic tin is 
deposited and the peroxide is found in solution. The solution of a stannous 
salt, and of a stannic salt also, is apt to undergo decomposition, when largely 
diluted with water, and to deposite a subsalt. The stannous salts absorb oxy- 
gen from the air, and have a great affinity for that element; they convert the 
peroxide of iron into protoxide, and throw down mercury, silver and plati- 
num in the metallic state from their solutions. The chloride of gold produces 
a purple precipitate in a stannous salt, consisting, '4, is believed, of the deu- 
toxide of tin in combination with protoxide of gold, a test by which the pro- 
toxide of tin may always be distinguished. The same oxide is precipitated 
as a black sulphuret, by sulphuretted hydrogen, even from acid solutions. 

Protochloride of tin, Salt of tin; SnCl + 3HO; 1178+337.5 or 94.39+ 
27. — This salt may be obtained in the anhydrous state by raising the tempe- 
rature of a mixture of equal weights of calomel and tin in a gradual manner,, and 
finally distilling the protochloride by a strong red heat.. The fused mass on 
cooling is a gray solid, of considerable lustre, and having the vitreous fracture. 
The hydrated chloride, known in commerce as salt of tin, is procured by evapo- 
rating the solution of tin in concentrated hydrochloric acid to the point of, 
crystallization. It is thus obtained in needles or in large four-sided prismatic 
crystals, which contain three atoms of water. The salt parts with the greater 
portion, if not the whole of this water at 212°, but if distilled at a higher 
temperature, loses hydrochloric acid also, and an oxichloride of tin remains. 
It dissolves completely in a small quantity of water; but when treated with a 
large quantity, the salt is partly decomposed, hydrochloric acid is dissolved, 
and a light milk-white powder separates, which is a basic chloride or oxichlo- 
ride, SnCl+SnO+2HO. Both the crystals and the solution absorb oxygen 
from the air, and then a basic salt of the peroxide is formed which is also inso- 
luble in water. From both these causes, a complete and clear solution of the 
salt of tin is rarely obtained, unless the water be previously acidulated with 
hydrochloric acid. This salt is entirely soluble in, caustic alkali, but the solu- 
tion is liable to an ulterior change already mentioned. The protochloride of 



PEROXIDE OF TIN. 417 

tin is not only used in calico printing as a mordant, but also as a deoxidizing 
agent, particularly to deoxidize indigo, and to reduce to a lower state of oxi- 
dation and discharge the peroxides of iron and manganese fixed upon cloth. 

Protochloride of tin and potassium; SnCl+KCl, «nrfSnCl+KCl+3HO. — 
The protochloride of tin forms a double salt with chloride of potassium, and 
also with chloride of ammonium, which crystallize in the anhydrous condition, 
and also with three atoms of water. 

The anhydrous protochloride of tin fused in ammoniacal gas, absorbs half 
an equivalent of that gas, according to Persoz, forming 2SnCl-f-NH 3 , or 
probable a double salt like the preceding salt of ammonium, that is, SnCl-f- 
(NH 3 Sn,)Cl. 

Protiodide of tin, SnI, is formed by heating a mixture of granulated tin 
and iodine. It was found by Boullay, jun., to form double salts with other 
iodides, particularly with the iodides of the alkaline and earthy metals, in 
which two atoms of the stannous iodide are combined with one of the other 
iodide. 

Carbonate of tin, Carbonic acid does not combine with either of the oxides 
of tin. 

Protosulphate of fin, SnO,S0 3 . — Tin dissolves in sulphuric acid concen- 
trated or a little diluted, and affords a saline mass, which forms a brown solu- 
tion in water and deposites small crystalline needles on cooling. 

Protonitrate of tin, SnO,NO_, is obtained by dissolving protoxide of tin 
in nitric acid; the solution cannot be concentrated and is easily altered. 

' Tartrate of potash and tin, KO,SnO-f(C 8 H 4 O 10 .) — Bitartrate of potash 
dissolves protoxide of tin, and forms a very soluble salt potash and of tin, 
which, like most of the tartrates, is neither precipitated by caustic alkalies, 
nor by alkaline carbonates. ' An addition of bitartrate of potash is occasionally 
made to the solution of tin used in dying. 

Deutoxide of tin, Sn 2 3 , 1770.6 or 141.88.— Was obtained by M. Fuchs, 
by diffusing recently precipitated peroxide of iron in a solution of protochlo- 
ride of tin, containing no excess of acid, and afterwards boiling the mixture. 
A double decomposition occurs, in which the deutoxide of tin precipitates, and 
protochloride of iron is retained in solution: 

2SnCl and Fe 2 3 = Sn 2 3 and 2FeCl. 

The deutoxide thus obtained is a slimy gray matter, and usually yellow from 
adhering oxide of iron. Ammonia dissolves it easily, and without a residue, 
which distinguishes this oxide from the protoxide of tin, the latter being .inso- 
luble, or almost so, in that menstruum. The deutoxide of tin is dissolved by 
concentrated hydrochloric acid; the taste of the solution is not metallic. It is 
distinguished from a salt of the peroxide of tin, by producing the purple pre- 
cipitate with chloride of gold. A sesquisulphuret exists, corresponding with 
this oxide. The salts of the deutoxide of tin have not been examined. 

Peroxide of tin, Stannic oxide, SnO,, 935.3 or 74.92.— -This constitutes 
the common ore of tin, which is generally crystallized. The crystals of tin 
stone are sometimes brownish yellow and translucent, at other times dark 
brown and almost black, and contain small quantities of protoxides of iron 
and manganese. Their primitive form is an obtuse octohedron of a square 
base; their density from 6.92 to 6.96. The peroxide of tin in this state does 
not dissolve in acids, unless previously ignited with an alkali. Tin is con- 
verted into a white powder, which is a hydrated peroxide, by nitric acid; and 
the acid acts with most violence, when not of its highest degree of concentra- 
tion. This oxide, after being well washed and dried, contains 11 per cent, of 
water; it reddens litmus paper. After ignition it assumes a pale yellow colour, 
and is equally insoluble, by the humid way, as the natural oxide. 



418 PERCOMPOUNDS OF TIN. 

To prepare the hydrated peroxide of tin, a solution of the bichloride of tin 
should be precipitated cold, by an alkaline carbonate, and washed with cold 
water. It forms a white and bulky gelatinous precipitate, which when col- 
lected on a filter has a certain degree of transparency. In this condition the 
peroxide of tin is readily dissolved by hydrochloric acid, whether concen- 
trated or in a diluted state. Dried in vacuo at the usual temperature, it forms 
hard translucent masses, resembling gum Arabic, which contain not more than 
1 eq. of water; and is not changed in properties by the desiccation. If this 
hydrated oxide be digested in boiling water and collected again on a filter, it is 
found, without much change in appearance, to be materially altered in proper- 
ties. The boiled oxide does not dissolve in undiluted hydrochloric acid, but 
forms with a small portion of it (about 14 per cent.) a salt insoluble in an ex- 
cess of acid. When the excess of acid is decanted, the residue then dissolves 
in pure water; but it precipitates from the solution when hydrochloric acid is 
added. If the aqueous solution is boiled, the oxide precipitates; and if the 
liquor is concentrated, it coagulates like albumen. There can be little doubt 
that the peculiarities of the boiled oxide are connected with an alteration in 
its state of hydration. Peroxide of tin, prepared by the action of nitric acid 
on tin, acquires the same properties, it is to be presumed, from its being ex- 
posed to a high temperature in its formation. The existence of two varieties 
of the peroxide of tin was observed by Berzelius so early as 1811, and is the 
first recorded instance of isomerism. 

Hydrochloric acid is capable of dissolving a great excess of hydrated per- 
oxide of tin, at least two or three equivalents. The peroxide of tin is also 
soluble in alkalies; and having in regard to them the powers of a feeble acid, 
it is sometimes called stannic acid. A very dilute solution of potash boiled 
with the peroxide of tin, forms a solution in which 1 part of potash may con- 
tain 16 parts of peroxide of tin. Peroxide of tin is employed in the prepara- 
tion of the white glass, known as enamel; and the ignited and finely levigated 
oxide forms jeweller's putty, which is used in polishing hard objects. The 
hydrated oxide resembles alumina in forming insoluble compounds with the 
organic colouring matters, and hence its salts are much prized as mordants. 

Bisulphuret of tin, SnS 2 , is precipitated from persalts of tin, of a dull yel- 
low colour, by sulphuretted hydrogen gas. Prepared in the dry way, by 
igniting a mixture of peroxide of tin, sulphur and sal-ammoniac in a covered 
crucible, it forms the aurum musivum or mosaic gold of the alchemists. In 
this operation the sal-ammoniac is indispensable, although it seems to serve no 
other purpose than to prevent the elevation of temperature which results from 
the sulphuration. Mosaic gold, when well prepared, has the yellow colour 
of gold, and consists of brilliant translucent scales, which are soft to the touch. 
No acid dissolves it, except aqua regia. It is decomposed by dry chlorine, 
and the compound formed, SnCl -J-2SC1 2 (page 273.) 

Bichloride of tin, Per muriate" of tin, SnCl 2 ; 1620.6 or 129.86.— -The an- 
hydrous bichloride of tin, known as the fuming liquor of Libavius, is procured 
by distilling, at a gentle heat, a mixture of 4 parts of corrosive sublimate with 
1 part of tin in filings, or tin amalgamated with a little mercury and then re- 
duced to powder. A colourless, highly limpid liquid is found in the con- 
denser, which fumes strongly in humid air. The bichloride boils at 248°; the' 
density of its vapour, observed by Dumas, is 9.1997. It forms a solid saline 
mass with one-third of its weight of water, and dissolves in a larger quantity 
of water. The same salt is obtained in solution, by conducting a stream of 
chlorine gas into a strong solution of the protochloride of tin, till the latter is 
saturated, which is shown by the solution ceasing to precipitate mercury from 
a solution of corrosive sublimate. A solution of this salt, extensively used in 
dying, and known as the nitro-muriate of tin, is generally prepared by oxi- 



ALLOYS OF TIN. 419 

dizing crystallized protochloride of tin by nitric acid; or by dissolving tin in a 
mixture of hydrochloric and nitric acids, avoiding any considerable elevation 
of temperature. 

Bichloride of tin and ammonia, SnCl 2 -f-NH 3 or (NH 3 Sn)Cl 2 . — Anhydrous 
bichloride of tin absorbs ammoniacal gas, and forms a white powder, which may 
be sublimed without decomposition ; after sublimation it is entirely soluble in 
water (Rose.) 

Bichloride of tin, and phosphuretted hydrogen, 3SnCl 2 +PH 3 . — These two 
bodies unite without the production of hydrochloric acid ; the compound is 
solid (Rose.) 

Bichloride of tin and potassium, SnCl 2 -fKCl. — The solution of bichloride 
of tin, when mixed with an equivalent quantity of chloride of potassium and 
evaporated, yields this double salt in regular octohedrons of a vitreous lustre, 
which are anhydrous. 

A sulphate and nitrate of peroxide of tin, have been crystallized ; this base 
forms no carbonate. 

Both the sulphuret and bisulphuret of tin, act as sulphur acids, combining 
with alkaline sulphurets. The bisulphuret of tin dissolves with digestion in sul- 
phuret of sodium, and the concentrated solution yields fine crystals of the salt, 
2NaS-fSnS 2 -|-12HO. The bisulphuret of tin is found combined with the sul- 
phurets of copper and iron, forming tin pyrites, a rare mineral, 2Fe.,S, SnS 2 + 
2Cu 2 S, SnS 2 . 

Alloys of tin. — Tin alloyed with small quantities of antimony, copper, and 
bismuth, forms the best kind of pewter, which possesses the peculiar whiteness 
of that metal. The most fusible compound of tin and bismuth, is that of an 
atom of each, metal, Bi Sn ; it melts at 289.4° (Rudberg.) When the metals 
are mixed in other ratios, a portion first congeals at a higher temperature, sepa- 
rating from the compound mentioned, which remains liquid till the temperature 
falls to 289.4°. Although tin precipitates copper from its solutions in acids, yet 
it is possible to precipitate tin upon copper, and to cover the latter with tin, as 
is proved by the tinning of pins. Tin is dissolved in a mixture of one part of 
bitartrate of potash, two of alum, two of common salt and a certain quantity of 
water, and the pins introduced at the boiling temperature. The pins undergo 
no change in this liquor, supposing it to contain no undissolved tin, but the mo- 
ment a fragment of tin touches the pins, all those in contact with each other 
are tinned. 

SECTION II. 

TITANIUM. 

Eq. 303.7 or 24.33 ; Ti. 

. This metal was discovered in 1791, by. Mr. Gregor, of Cornwall, and after- 
wards by Klaproth who gave it the name of titanium. In the form of titanic 
acid it constitutes several minerals, as rutile, anatase, menachanite, etc ; and as 
titanate of protoxide of iron, ilmenite and other species. 

Titanic acid, mixed with one-sixth of its weight of charcoal powder may be 
reduced by the most intense heat of a wind furnace, which does not, however, 
fuse the titanium. It is frequently found in small cubic crystals of a bright cop- 
per colour, on the slag which adheres to the lower part of the iron smelting fur- 
naces. T.he iron and foreign matter of the slag may be removed by digestion 
in acids; and the crystals obtained in a separate state. Their density is 5.3 ; 
they are harder than quartz. Titanium is not dissolved by any acid, except a 



420 TITANIUM. 

mixture of nitric and hydrofluoric acids. It is slowly oxidated in fused nitre. 
Titanium combines in two proportions with oxygen, forming titanic oxide TiO, 
and titanic acid Ti0 2 . 

Oxide of titanium, TiO, 403.7 or 32.33.— Is formed when titanic acid is ex- 
posed in a charcoal crucible, to the highest temperature of a wind furnace. 
Where the acid was in contact with the charcoal, a thin coating of red metallic ti- 
tanium is formed, but within it is changed into a black mass, which is insoluble 
in all acids, and not otherwise affected by them, is oxidated with difficulty when 
heated in contact with air, or by fusion with nitre. The oxide of titanium is 
also obtained by the moist way, in the form of a deep purple powder, when a 
fragment of zinc or iron is introduced into a solution of titanic acid in hydro- 
chloric acid, but alters so quickly by absorption of oxygen, that an opportunity 
has not been obtained of studying its properties. The composition assigned to 
it above is, therefore, hypothetical. 

Titanic acid, Ti0 2 , 503.7 or 40.33. — In the mineral rutile, titanic acid is 
crystallized in the form of tin stone; the link by which tin is connected with ti- 
tanium. Again ilmenite and other varieties of titanate of iron, FeO,Ti0 2 , are 
isomorphous with peroxide of iron, (page 122 ;) and thus tin comes to be con- 
nected through titanium with the last order of metals. But titanic acid is di- 
morphous, and crystallizes, in anatase, in an unconnected form. Titanic acid 
is produced more easily from the titanate of iron, reduced to powder and levi- 
gated, which is fused with sulphur. The sulphur has no action upon the titanic 
acid, but converts the protoxide of iron into a sulphuret of iron, which is dis- 
solved by hydrochloric acid. If iron is still retained by the titanic acid, the lat- 
ter is heated in a stream of sulphuretted hydrogen gas, by which every particle 
of iron is convertedjinto sulphuret, and then removed by hydrochloric acid. 

Titanic acid is a white powder, which acquires a yellow tint by a high tem- 
perature ; it is infusible and insoluble in water. Titanic acid is considerably 
analogous in properties to silica ; like that acid it has a soluble modification, 
formed by igniting titanic acid with an alkaline carbonate, which is soluble in 
dilute hydrochloric acid. The acid solution of titanic acid gives an orange-red 
precipitate with an infusion of gall-nuts, which is characteristic of titanic acid. 
On neutralizing the acid solution with ammonia, the soluble modification of 
titanic acid is thrown down as a white gelatinous precipitate. When this pre- 
cipitate is dried and heated, it glows, and the titanic acid is no longer soluble 
in acids. When a solution of bichloride of titanium, or of the sulphate of ti- 
tanic acid in water, is boiled for some time, titanic acid precipitates in the 
insoluble modification. 

Bisulphuret of -titanium, TiS 2 , was discovered by Rose who formed it by 
passing the vapour of the bisulphuret of carbon over titanic acid, in a porcelain 
tube maintained at a bright red heat 

Bichloride of titanium, TiCl 2 , was formed by Mr. George, of Leeds, by 
transmitting chlorine over metallic titanium at a red heat. It is a transparent 
colourless liquid resembling bichloride of tin, and boiling a little above 212°. 
The density of its vapour is 6.615 (Dumas.) Bichloride of titanium combines 
with ammonia, and forms a white saline mass, TiCl 2 -f 2NH 3 . Metallic titanium 
is most easily obtained by heating this compound to redness. Bichloride of ti- 
tanium also absorbs phosphuretted hydrogen, and forms a dry brown powder. 
From this compound when heated, a lemon yellow sublimate rises, which Rose 
found to contain 3 atoms of bichloride of titanium, combined with one atom of 
a compound of phosphuretted hydrogen and hydrochloric acid, analogous to 
sal-ammoniac, but which could not be isolated. Bichloride of titanium forms 
double salts with the alkaline chlorides, which are colourless and capable of 
crystallizing. 

A volatile bifluotide of titanium, TiF 2 , was obtained, by Unverdorben, by 



CHROMIUM. 421 

distilling titanic acid in a platinum apparatus with fluor spar in powder, and 
fuming sulphuric acid. 

A definite sulphate of titanic acid, Ti0 3 -f- SO 3 , is obtained by dissolving 
titanic acid in sulphuric acid, and evaporating to dryness by a heat under 
redness. 

SECTION III. 

CHROMIUM. 

Eq. 351.8 or 28.19; Cr. 

This metal, so remarkable for the variety and beauty of its coloured prepa- 
rations, was discovered by Vauquelin in 1797, in the red mineral known as 
chromate of lead. It has since been found in other minerals, more particularly 
chrome iron (FeO-}-Cr 2 O v ) a mineral which many countries possess in con- 
siderable quantity. It is from this ore that the compounds of chromium, used 
in the arts, are actually derived. The metal may be procured by the reduction 
of its oxide, in the usual way, but with the same difficulty as manganese. 
Chromium is a grayish white metal, of density 5.9, fusible with the greatest dif- 
ficulty, and not magnetic. It does not undergo oxidation in the air ; it dissolves 
in hydrofluoric acid with evolution of hydrogen. Chromium is also obtained as 
a brown powder, when sesquichloride of chromium is heated in ammoniacal 
gas, (Liebig.) Chromium forms two compounds with oxygen, of which the lower, 
or oxide of chromium, Cr 2 3 , is isomorphous with peroxide of iron and alumina, 
and the higher or chromic acid, Cr0 3 , is isomorphous with sulphuric acid. 

Oxide of chromium, Cr 2 O s ; 1003.6 or 80.42. — This oxide exists in 
chrome iron, but is not immediately derived from that mineral. When chro- 
mate of mercury, the orange precipitate obtained on mixing nitrate of mercury 
and chromate of potash, is strongly ignited, oxide of chromium remains as a 
powder of a good green colour. The oxide of chromium is also obtained by- 
deoxidizing the chromic acid of bichromate of potash in various ways; by igni- 
tion with sulphur, for instance, or by igniting together 1 part of bichromate 
of potash with 1$ parts of sal ammoniac, and 1 part of carbonate of potash, 
whereby chloride of potassium and oxide of chromium are formed; the chro- 
mic acid losing half its oxygen which is converted into water by the hydrogen 
of the ammonia. Another process, interesting from affording the oxide in the 
state of crystals, is to pass the vapour of chloro-chromic acid (Cr0 2 Cl) 
through a tube heated to whiteness, when oxygen and chlorine gases are dis- 
engaged, and oxide of chromium attaches itself to the surface of the tube. 
The crystals have a metallic lustre, and are of so deep a green as to appear 
black; they have the same form as specular iron ore, the density 5.21, and are 
as hard as corundum (Wdhler.) The ignited oxide of chromium is not solu- 
ble in acids; heated with access of air, and in contact with an alkali, it ab- 
sorbs oxygen and becomes chromic acid. Fused with borax or other vitreous 
substances, oxide of chromium communicates to them a beautiful green colour; 
it is the colouring matter of the emerald, and is employed to produce a green 
colour upon earthenware. Oxide of chromium (and not chromic acid) is also 
the colouring matter of pink colour, applied to stoneware. This substance is 
formed by igniting strongly a mixture of 100 parts of peroxide of tin, 33 parts 
of chalk and not more than 1 part of oxide of chromium.* 

* Malaguti, An. de Chim. et de Phys. t. 61, p. 433. Mr. O. Sims finds that peroxides of 
iron and manganese may be substituted for oxide of chromium in pink colour, so that the 
colouration of that substance is of an extraordinary character. 
36 



422 OXIDE OF CHROMIUM. 

To obtain the same oxide in a hydrated condition, a solution of bichromate 
of potash is brought to the boiling point, and hydrochloric acid and alcohol 
alternately added in small quantities, till the solution passes from a red to a deep 
green colour, and no longer effervesces from the escape of carbonic acid gas, 
upon the addition of either the acid or alcohol. In this experiment the chro- 
mic acid, liberated by the hydrochloric acid, is deprived of half its oxygen by 
the hydrogen and carbon of the alcohol, and the resulting oxide of chromium 
is dissolved by the excess of hydrochloric acid present, and in fact converted 
into the corresponding sesquichloride of chromium. Many other organic sub- 
stances may be used in place of alcohol in this experiment, such as sugar, 
oxalic acid, &c. The oxide of chromium is precipitated from the green solu- 
tion by ammonia, and falls as a pale bluish-green hydrate. The same oxide 
is obtained more directly, when to a boiling solution of bichromate of potash, a 
hot solution of the pentasulphuret of potassium is added, the chromic acid then 
giving half its oxygen to the sulphur. 

Hydrated oxide of chromium is soluble in acids, and forms salts. It is also 
dissolved by potash and soda, but not to a great extent by ammonia. Its solu- 
tion in acids is generally green or purple by reflected, and red by transmitted 
light. Its salts have a sweet taste, and are poisonous; they are not affected 
by sulphuretted hydrogen; alkaline sulphurets precipitate from them the hy- 
drated oxide. The oxide itself becomes of a greener colour when dried, and 
loses water. A moderate heat affects its relations to acids, the sulphate of the 
heated (or green) oxide not forming a double salt, for instance, with sulphate 
of potash. When heated to redness, it glows, or undergoes the same change 
as zirconia, peroxide of tin, and many other hydrated peroxides when made 
anhydrous, becomes denser, of a pure green colour, and ceases to be soluble 
in acids. 

A sesquisulphuret of chromium, Cr 2 S 3 , corresponding with the oxide, is 
obtained by exposing the latter, in a porcelain tube, to the vapour of bisul- 
phuret of carbon, at a bright red heat. It is a substance of a dark gray colour, 
which is dissolved by nitric acid. 

Sesquichloride of chromium, Cr 2 Cl 3 ; 2031.6 or 162.79. — This salt is ob- 
tained as a sublimate of a peach-purple colour, when chlorine is passed over a 
mixture of oxide of chromium and charcoal, ignited in a porcelain tube: or, by 
evaporating the solution of sesquichloride of chromium to dryness. The salt 
obtained by the latter process is a green powder, and retains 3HO at 212°; 
above 400° it loses water and becomes anhydrous, assuming the same colour 
as the sublimed chloride. In the anhydrous state it dissolves very slowly in 
water. 

Sulphate of chromium, Cr 2 3 ,3S0 3 ; 2507.1 or 200.90.— Oxide of chro- 
mium is dissolved by sulphuric acid, but the salt does not crystallize. When 
dried strongly, it loses its solubility. It forms, however, a crystallizable 
double salt with sulphate of potash, chrome alum, KCSOg-fC^Og^SOg-f 
24HO. This salt appears when a mixture of its constituent salts, with a little 
free sulphuric acid, is left to spontaneous evaporation. Its octohedral crystals 
are of a dark purple colour, and of a beautiful ruby-red, when so small as to 
be transparent. . The solution of chrome alum is bluish-purple, but when 
heated to 140° or 180° becomes green, a change of colour which indicates the 
decomposition of the salt; for when afterwards evaporated, it no longer yields 
crystals of chrome alum, but of sulphate of potash, and the sulphate of chro- 
mium dries up into a gummy mass. Iron alum is decomposed in the same 
manner, by heating its solution, and is not reproduced on cooling. The best 
mode of preparing chrome alum is. to mix three parts of a saturated solution 
of neutral chromate of potash, first with one part of oil of vitriol, and then 
with two parts of alcohol, which is added by small portions to the mixture of 



SALTS OF OXIDE OF CHROMIUM. 423 

acid and chromate, and not to apply artificial heat. The chromic acid is thus 
deoxidized in a gradual manner, and large cr) T stals of the double sulphate are 
slowly deposited, (Fischer.) 

Oxalateofehromiumandpota8h,^KO,G 2 3 )+Cr 2 3 ,3C 3 3 + 6H.O.-- 
This is another beautiful double salt of chromium. It is easily prepared by 
the following process of Dr. Gregory. One part of bichromate of potash, two 
parts of binoxalate of potash, and two of crystallized oxalic acid are dissolved 
together in hot water. A copious evolution of carbonic acid gas takes place, 
arising from the deoxidation of the chromic acid, at the expense of a portion 
of the oxalic acid, and nothing fixed remains, except the salt in question, of 
which a pretty concentrated solution crystallizes upon cooling in prismatic 
crystals, which are black by reflected light, but of a splendid blue by trans- 
mitted light, when sufficiently thin to be translucent. The oxide of chro- 
mium cannot be precipitated from this salt completely by an alkaline carbonate; 
and it is remarkable that only a small portion of the oxalic acid is thrown 
down from it by chloride of calcium. When fully dried and then carefully 
ignited, this salt is completely decomposed, and leaves a mixture of chromate 
and carbonate of potash. The corresponding double oxalate of chromium and 
soda contains 9HO, according to Mitscherlich. In the analogous oxalate of 
peroxide of iron and soda, the proportion of water appeared to me to be 
10HO. 

The mineral chrome iron, FeO,Cr 2 3 , crystallizes in octohedrons, and 
corresponds with the magnetic oxide of iron, having the peroxide of iron re- 
placed by oxide of chromium. Its density is 4.5; it is about as soft as felspar, 
and infusible. When exposed to long-continued calcination, in contact with 
carbonate of potash, in a reverberatory furnace, the oxide of chromium of this 
compound absorbs oxygen, and combines as chromic acid with the potash, 
while the protoxide of iron becomes peroxide. The addition of nitre increases 
the rapidity of oxidation, but is not absolutely required in the process. A 
yellow alkaline solution of carbonate and chromate of potash is obtained by 
lixiviating the calcined matter, which is generally converted into the red chro- 
mate or bichromate of potash, by the addition of the proper quantity of sul- 
phuric acid, the latter salt being more easily purified by crystallization than 
the neutral chromate. 

Chromic acid, CrO,, 651.8 or 52.19. — This acid is not liberated from 
the chromates in a state of purity by any acid except the fluosilicic; it is 
also easily altered. Fluosilicic acid gas is conducted into a warm solution of 
bichromate of potash, till the potash is completely separated as the insoluble 
fluoride of silicon and potassium, which may be ascertained by testing a few 
drops of the solution with tartaric acid or chloride of platinum. The solution 
is evaporated to dryness by a steam heat, and the chromic acid redissolved by 
water; it gives an opaque dull red solution. Chromic acid may also be ob- 
tained anhydrous and in acicular crystals, by distilling, in a platinum retort, a 
mixture of 4 parts of chromate of lead, 3 parts of finely pulverized fluor spar, 
and 7 parts of the Nordhausen sulphuric acid; sulphate of lime is formed, and 
the superfluoride of chromium, the vapour of which is received in a large pla- 
tinum crucible, covered by wet paper, and used as a condenser. The super- 
tluoride is decomposed by the aqueous vapour from the paper, being resolved 
into hydrofluoric acid and beautiful orange-red acicular crystals of chromic 
acid, which fill the crucible. Chromic acid differs remarkably from sulphuric 
acid, in having but little affinity for basic water, so that it may be obtained 
anhydrous by evaporating its solution to dryness. Indeed, the chromate of 
water is not known to exist, even in combination, both the bichromate and 
terchromate of potash being anhydrous salts. The free acid is a highly oxi- 
dating agent, and bleaches organic colouring matters: chromic acid then loses 



424 CHROMATES. 

half its oxygen, and becomes oxide of chromium. When sulphurous acid is 
transmitted through the solution of a chromate, a brown precipitate subsides, 
which is a subchromate of the oxide of chromium. The same compound fre- 
quently appears when chromic acid is otherwise imperfectly deoxidized. 



CHROMATES. 

Chromate of potash , Yellow chromate. of potash, KO,Cr0 3 ; 1241.7 or 
99.5.— This salt is produced in the treatment of the chrome ore, but is seldom 
crystallized. It may be formed from the bichromate, by fusing that salt with 
an equivalent quantity of carbonate of potash; or by adding caustic potash to 
a red solution of the bichromate, till its colour becomes a pure golden yellow. 
The solution of chromate of potash has a great tendency to effloresce upon 
the sides of the basin when evaporated. Its crystals are of a yellow colour, 
anhydrous, and isomorphotis with sulphate of potash. One hundred parts of 
water at 10° dissolve 48| parts of this salt; the solution preserves its yellow 
colour, even when diluted to a great degree. 

Bichromate of potash, Bed chrcDnate of potash, KO,2Cr0 3 ; 1893.5 or 
151.73. — This beautiful salt, of which a large quantity is consumed in the arts, 
crystallizes in prisms, or in large four-sided tables, of a fine orange-red colour. 
It fuses under a red heat, and forms a crystalline mass on cooling, of which 
the crystals have the same form as those obtained from an aqueous solution, 
according to Mitscherlich; but this mass falls to powder as it cools, from the 
unequal contraction of the crystals in different dimensions. At 60°, water 
dissolves l-10th of its weight of this salt, and at the boiling point a conside- 
rably greater quantity. 

Bichromate of chloride of potassium, Peligot's salt, KCl-4-2CrO r — This 
salt, which we are obliged to designate as if it contained chloride of potassium 
in combination a^ a base with chromic acid, is formed by dissolving together 
with the aid of heat, about three parts of bichromate of potash and four of con- 
centrated hydrochloric acid, with a small quantity of water, avoiding the evo- 
lution of chlorine. It crystallizes in flat red quadrangular prisms, and is de- 
composed by solution in pure water. 

Ter chromate. of pot ash % K0,3CrO 3 , is obtained crystallized when a solu- 
tion of the bichromate is mixed with nitric acid, and evaporated. Bichromates 
of soda and of silver exist, which are anhydrous, like the bichromate of potash, 
(Warington.) 

Chromate of soda, NaO,CrO 3 + 10H().. — By the evaporation of a concen- 
trated solution of this salt, it is obtained in large fine crystals, having the form 
of glauber salt. 

Chromate of lead, PbO,Cr0 3 ; 2046.3 or 163.97.— This compound, so well 
known as chrome yellow, is obtained by mixing the nitrate, or acetate of lead, 
with the chromate or bichromate of potash. The precipitate is of a lighter 
shade from dilute than from concentrated solutions. It is entirely soluble in 
potash or soda, but not in dilute acids. 

Subchromate of lead, 2PbO,Cr0 3 , is of a red colour. It is formed when a 
solution of neutral chromate of potash, with as much free alkali added to it as 
it already contains, is added to a solution of nitrate of lead. But the finest 
vermillion-red subchromate is formed when one part of the neutral chromate 
of lead is thrown into five parts of nitre, in a state of fusion by heat. Water 
dissolves the chromate and nitrate of potash of the fused mass, and leaves the 
subchromate of lead, as a crystalline powder, (Liebig and Wohlen) An 
orange pigment may be obtained very economically by boiling the sulphate of 
lead, which is a waste product in making acetate of alumina from alum by 



VANADIUM, 425 

means of acetate of lead, with a solution of chromate of potash. The subchro- 
mate of lead forms a beautiful orange upon cloth, which is even more stable 
than the yellow chromate, not being acted upon by either alkalies or acids. 
One method of dying chrome orange, is to fix the yellow chromate of lead 
first in the calico, by dipping it successively in acetate of lead and bichromate 
of potash, and then washing it. This should be repeated, in order to preci- 
pitate a considerable quantity of the chromate in the calico. A milk of lime 
is then heated in an open pan, and when at the point of ebullition, the yellow 
calico is immersed in it, and instantly becomes orange, being deprived of a 
portion of its chromic acid by the lime, which forms a soluble chromate of 
lime. At a lower temperature, lime-water dissolves the chromate of lead 
entirely, and leaves the cloth white. 

Chromate of silver falls as a reddish brown precipitate when nitrate of silver 
is added to neutral chromate of potash. Dissolved in a hot and concentrated 
solution of ammonia, it gives, on cooling, large well-formed crystals, AgO, 
Cr0 3 -f 2NH 3 , isomorphous with the analogous ammoniacal sulphate and se- 
leniate of silver. 

Chromate of magnesia forms, according to my own observations, yellow 
crystals which are very soluble, and contain 5HO. It does not form a double 
salt with chromate of potash, as sulphate of magnesia does with sulphate of 
potash. It is remarked that the insoluble metallic chromates generally carry 
down portions of the neutral precipitating salts, or of subsalts, and their analysis 
is often unsatisfactory from that cause. When the magnesian chromates are 
compared with the sulphates of the same family, the former are found to have 
their water readily replaced by metallic oxides, but not by salts; so that sub- 
chromates with excess of oxide are numerous, while kw or no double chro- 
mates exist. 

Chlorochromic acid, Cr0 2 Cl, or 2Cr0 3 +OCl v — This is a volatile liquid, 
obtained by distilling, in a glass retort, by a gentle heat, 3 parts of bichromate 
of potash and 31 parts of common salt, previously reduced to powder and 
mixed together, with 5 parts by water measure, of oil of vitriol, discontinuing 
the distillation when the vapours, from being a deep orange-red, become pale — 
that change arising from watery vapour. The compound is a heavy red liquid, 
decomposed by water. The density of its vapour is 5.9. 

Terfluoride of chromium, CrF^, is obtained in the manner already mentioned 
under the preparation of chromic acid. It is a blood-red liquid. No corre- 
sponding terchloride of chromium has been obtained in an isolated state. 



SECTION IV. 

VANADIUM. 

Eq. 856.9 or 68.66 ; V. 

Vanadium, so named from Vanadis, a Scandinavian deity, was discovered 
by Sefstrcem, in 1830, in the iron prepared from the iron ore of Taberg, in 
Sweden, and procured afterwards in larger quantity from the slag of that ore. 
It was found afterwards by Mr. Johnston, in a new mineral discovered by him, 
the vanadiate of lead from Wanlockhead. It is one of the rarest of the ele- 
ments. The metal itself has considerable resemblance in properties to chro- 

36* 



426 TUNGSTEN. 

mium. It combines with oxygen in three proportions, forming the protoxide 
of vanadium, VO, peroxide, V0 2 , and vanadic acid, V0 3 . 

Protoxide of vanadium, VO, 956. 9 or 76.66, is produced by the action of 
charcoal or hydrogen upon vanadic acid. It is a black powder of semi-metallic 
lustre, and when made coherent by pressure, conducts electricity like a metal. 
It does not combine with acids, and exhibits none of the characters of an alka- 
line base. It is readily oxidized when heated in the open air, and passes into 
the following compound. 

Peroxide of vanadium, V0 2 , 1056.9 or 84.66 — is produced by the action of 
sulphuretted hydrogen and other deoxidating substances upon vanadic acid. 
When pure, it is a black pulverulent substance, quite free from any acid or 
alkaline reaction. It dissolves in acids, and forms salts, most of which are of a 
blue colour. These salts give a precipitate with a slight excess of carbonate 
of soda, of a grayish- white hydrate, which becomes red by oxidation. They 
are also precipitated black by infusion of nutgalls, like the salts of iron. Per- 
oxide of vanadium is also capable of acting as an acid, and forms compounds 
with alkaline bases, some of which are crystallizable. 

Vanadic acid, V0 3 ; 1156.9 or 92.66. — It is in this state that vanadium 
occurs in the slag of the iron of Taberg, and in the vanadiate of lead. It is 
obtained by dissolving the latter mineral in nitric acid, and precipitating the 
lead and arsenic, with which the vanadium is accompanied, by sulphuretted 
hydrogen. A blue solution of peroxide of vanadium remains, which becomes 
vanadic acid when evaporated to dryness. Vanadic acid fuses but retains its 
oxygen at a strong red heat. It is very sparingly soluble, water taking up only 
1-1 00th of its weight of this compound, acquiring a yellow colour and an acid 
reaction. It acts the part of a base to stronger acids. An interesting double 
phosphate of silica and vanadic acid was observed in crystalline scales, of 
which the formula is 2SiO s , P0 5 +2V0 3 , P0 5 -f 6HO. Vanadic acid forms 
with bases neutral and acid salts, the first of which admit of an isomeric modifi- 
cation, being both white and yellow, while the acid salts are of a fine orange- 
red. Vanadic and chromic acids are the only acids of which the solution is 
red, while they are distinguished from each other by the vanadic acid becoming 
blue, and the chromic acid green, when they are deoxidized. 

Sulphurets and chlorides of vanadium, corresponding with the peroxide 
and vanadic acid, have likewise been formed.* 



SECTION Y. 

TUNGSTEN AND MOLYBDENUM. 

TUNGSTEN. 

Syn. wolfram. Eq. 1183 or 94.8; W. 

This element exists in the form of tungstic acid in several minerals, of which 
the most important are the native tungstate of lime CaO,W0 3 , and wolfram, 
or the tungstate of manganese and iron, MnO,W0 3 -f 3(FeO,W0 3 .) Its 
name tungsten means in Swedish, heavy stone, and is expressive of the great 
density of its preparations. 

* Berzelius, Aa. de Ch, et de Ph. t. 47, p. 337. 



TUNGSTEN. 42? 

Tungstic acid parts with oxygen easily, and may be reduced in a glass 
tube, by means of dry hydrogen gas, at a red heat. This metal is thus ob- 
tained in the state of a dense dark gray powder, which it is necessary to ex- 
pose to a very violent heat to fuse into globules, for tungsten is even less fusi- 
ble than manganese. The metal, when fused, has the colour and lustre of 
iron, and is not altered in air: it is, after gold and platinum, the densest of the 
metals, the specific gravity of tungsten being from 17.22 to 17.6. When 
heated to redness, in the pulverulent form, it takes fire, burns, and becomes 
tungstic aeid. Tungsten forms two compounds with oxygen, tungstic oxide, 
W0 2 and tungstic acid, WO v 

Tungstic oxide, W0 2 , 1383 or 110.8. — This oxide is obtained as a brown 
powder when tungstic acid is reduced by hydrogen at a temperature not ex- 
ceeding low redness. Tungstic acid may also be deprived of oxygen in the 
humid way, by pouring diluted hydrochloric acid over it, and placing zinc in 
the liquor; the tungstic acid then gradually changes into tungstic oxide, in the 
form of brilliant crystalline plates of a copper-red colour. No saline com- 
pounds of this oxide with acids are known. When digested in a strong solu- 
tion of hydrate of potash, it dissolves, with the disengagement of hydrogen gas, 
and the formation of tungstate of potash. 

A compound of tungstic oxide and soda, NaO+2W0 2 , of a very singular 
nature, was discovered by Wohler. It is obtained by adding to fused tung- 
state of soda as much tungstic acid as it will take up, and exposing the mass 
at a red heat to hydrogen gas. After dissolving out the neutral undecomposed 
tungstate by water, the new compound remains in golden yellow scales and 
regular cubes, possessing the metallic lustre and a striking resemblance to 
gold. This compound is not decomposed by aqua regia, sulphuric or nitric 
acid, nor by alkaline solutions, but yields to hydrofluoric acid. It cannot be 
prepared by uniting soda directly with tungstic oxide. 

Tungstic acid, W0 3 ; 1483 or 118.8 — is most conveniently obtained by 
decomposing the native tungstate of lime, finely pulverized, by hydrochloric 
aeid; chloride of calcium is dissolved, and tungstic acid precipitates. Dis- 
solved in ammonia and precipitated again by acids, tungstic acid always forms 
a compound with the acid employed. It may be obtained in a separate state 
by heating the tungstate of ammonia to redness. It is an orange yellow 
powder, which becomes dull green when strongly heated. Its density is 
6.12. It is quite insoluble in water or in acids, but dissolves in alkaline solu- 
tions. 

Tungstic acid forms both neutral and acid salts with the alkalies. The 
tungstate of potash is a very soluble salt, which may be obtained in small 
crystals by the evaporation of its solution. When a little acid is added to the 
solution, an acid salt precipitates, which is very slightly soluble in water. 
The tungstate of soda is also very soluble, but maybe obtained in good crys- 
tals, which contain a large quantity of water of crystallization. The acid 
tungstate of soda is very crystallizable, and soluble in eight parts of water. A 
combination of tungstic acid with tungstic oxide, W0 2 ,W0 3 , is obtained as 
a fine blue powder when the tungstate of ammonia is heated to redness in a 
retort, and is also produced in other circumstances. Malaguti is disposed to 
consider this compound as a distinct acid of tungsten, W 2 5 (An. de Ch. et 
de Ph. lx. 271.) 

Sulphurets of tungsten. — The bisulphuret is prepared by mixing one part 
of tungsten with six parts of cinnabar, and exposing the mixture, covered with 
charcoal in a crucible, to a white heat. The tersulphuret is formed by dis- 
solving tungstic aeid in an alkaline sulphuret, and precipitating by an acid. It 
is of a liver-brown colour, and becomes nearly black on drying. The tersul- 
phuret of tungsten has a certain degree of solubility in water containing no 



428 MOLYBDENUM. 

saline matter, and is a strong sulphur acid. The salt KS,WS 3 forms pale 
red crystals. Two parts of this sulphur salt dissolved in water with one 
part of nitre, give large and beautiful rubv-red crystals of a double salt, 
KS,WS 3 , + KO,N0 5 . 

Bichloride of tungsten, WC1 2 , is formed when metallic tungsten is heated 
in chlorine gas. It condenses in dark red needles, which are very fusible and 
volatile. This chloride is decomposed by water, and tungstic oxide with 
hydrochloric acid formed. 

Ter chloride of tungsten, WCl,, is produced at the same time as the last 
compound, and also when the sulphuret of tungsten is heated in chlorine gas. 
It forms a sublimate of beautiful red crystals, which are resolved by water into 
tungstic and hydrochloric acids. A chlorotungstic acid, or double compound 
of terchloride of tungsten and tungstic acid, W0 2 C1, or WCJ 3 -f2WO;,, is pre- 
pared by heating tungstic oxide in chlorine gas. It condenses in yellow crys- 
talline scales: when suddenly heated, it is resolved into tungstic acid, bichloride 
of tungsten, and chlorine. Another compound is known, 2WCl 3 -fW0 3 
(Bonnet.) 



MOLYBDENUM. 



Eq. 598.5 or 47.96; Mo. 

This metal is closely allied to tungsten. Its native sulphuret was first dis- 
tinguished from plumbago by Scheele, in 1778; and a few years afterwards, 
molybdic acid, which he had formed, was reduced, and molybdenum obtained 
from it, by another Swedish chemist, Hjelm. The name molybdenum is derived 
from the .Greek term for plumbago. 

The oxides of molybdenum are easily reduced, when exposed to a strong 
heat in a crucible lined with charcoal, but the metal itself is very refractory. 
Bucholz, who obtained it in rounded buttons, found it to be a white metal, of 
density between 8.615 and 8.636. It is not acted upon by hydrochloric, hydro- 
fluoric, or diluted sulphuric acid; but is dissolved by concentrated sulphuric 
acid, by nitric acid, and aqua regia. Hydrate of potash does not dissolve this 
metal by the humid way. It combines in three proportions with oxygen, form- 
ing molybdous oxide, MoO, Molybdic oxide, Mo0 2 , and molybdic acid, Mo0 3 . 

Molybdous oxide, MoO, 698.5 or 55.96. — This oxide is obtained by adding 
to the concentrated solution of any molybdate, so much hydrochloric acid as to 
redissolve the molybdic acid which is at first thrown down, and placing zinc in 
the liquid ; this becomes first blue, then reddish-brown, and finally black, and 
contains the chloride of zinc and protochloride of molybdenum. To separate 
the oxide of molybdenum from the oxide of zinc, ammonia is added to the liquid 
in quantity no more than sufficient to precipitate the former, while the latter 
remains in solution. The molybdous oxide carries down with it a portion of 
oxide of zinc, from which it may be freed by washing with ammonia: it is thus 
obtained as a hydrate of a black colour. The hydrate of molybdous oxide dis- 
solves with difficulty in acids, forming solutions which are almost black and 
opaque, and which do not yield crystallizable salts. It is not dissolved by 
potash, nor by the fixed alkaline carbonates ; but, on the contrary, is soluble in 
carbonate of ammonia, when freshly precipitated. Molybdous oxide resists, 
after ignition, the action of all acids. 

Molybdic oxide, Mo0 2 ; 798.5 or 63,96. — This oxide may be obtained by 
igniting molybdate of ammonia in a covered crucible, but mixed with a little 
molybdic acid. It is better procured by igniting rapidly, in a covered crucible. 



MOLYBDIC ACID. 429 

a mixture of anhydrous molybdate of soda (which may contain an excess of 
soda) with sal ammoniac. Water poured upon the fused mass dissolves com- 
mon salt, and leaves a brown powder almost black. But molybdic oxide pre- 
pared in this way is insoluble in acids. The hydrated oxide may be obtained 
in various ways, one of which consists in digesting molybdic acid with hydro- 
chloric acid and copper, till all the molybdic acid is dissolved. From the solu- 
tion, which is of a deep red colour, molybdic oxide is precipitated in appearance 
exactly similar to the hydrated peroxide of iron, by ammonia, added in sufficient 
excess to retain all the oxide of copper in solution. The hydrate has a certain 
degree of solubility in pure water, and should, therefore, be washed with a solu- 
tion of sal ammoniac, and lastly by alcohol. This hydrate reddens litmus 
paper, but possesses no other property of an acid. It is not dissolved by the 
hydrated alkalies, but is soluble in their carbonates, like several earths and 
metallic oxides. It dissolves in acids and forms salts, which are red when they 
contain water of crystallization, and black when anhydrous. The oxalate of 
molybdic oxide can be obtained in crystals by spontaneous evaporation. 

Molybdic acid, Mo0 3 ; 898.5 or 71.96.— The native sulphuret of molyb- 
denum, in fine powder, is roasted in an open crucible, with constant stirring, at a 
heat not exceeding low redness, so long as sulphurous acid comes off. It leaves 
a dull yellow powder, which is impure molybdic acid. This is dissolved in 
ammonia, and the molybdate of ammonia purified by evaporation, during which 
some foreign matters are deposited and crystallized. The crystallized salt, ex- 
posed to a moderate heat, so as to avoid fusion, loses its ammonia, and leaves 
molybdic acid in a state of purity. The acid thus prepared is a white and light 
porous mass, which may be diffused in water, and divides into little crystalline 
scales of a silky lustre. It fuses at a red heat, and forms on cooling a straw- 
coloured crystalline mass, of which the density is 3.49. This acid forms no hy- 
drate. It requires 570 times its weight of water to dissolve it. Before being 
ignited, it is soluble in acids, and forms a class of compounds, in which it ap- 
pears to play the part of base, but of which not much is known. When boiled 
with bitartrate of potash, molybdic acid dissolves, even after being fused by 
heat. 

When a solution of bichloride of molybdenum is poured into a solution satu- 
rated, or nearly so, of molybdate of ammonia, a blue precipitate falls, which is 
a molybdate of molybdic oxide, M0 o ,3M0 3 . This compound is likewise readily 
formed in a variety of other circumstances* The salts of molybdic acid are colour- 
less, when their base is not coloured. When they are treated with other acids, 
molybdic acid precipitates, which dissolves, however, in an excess of the acid, 
except in nitric acid. It forms both neutral and acid salts with the alkalies. 
Molybdate of potash is formed by dissolving molybdic acid in carbonate of pot- 
ash ; it is easily soluble in water and crystallizable. Molybdate of soda has the 
same form, and resembles in properties the tungstate of soda. Bimolybdate of 
soda crystallizes in large fine crystals, which effloresce in air. Molybdate of 
magnesia is soluble in twelve or fifteen times its weight of water, and may be 
crystallized. Molybdate of lead occurs finely crystallized as a mineral. Chro- 
mate of lead is dimorphous, and corresponds in the least usual of its forms with 
molybdate of lead : hence molybdenum is connected with the magnesian metals, 
and tungsten also with the same class, from the isomorphism of the tungstates 
and molybdates. 

Sulphurets of molybdenum. — The bisulphuret is the ore from which the 
compounds of this metal are derived. It occurs in many parts of Sweden, and 

* It will be observed, that the atom of this compound contains three atoms of metal, so 
also does the remarkable combination of tungstic oxide and soda, (page 427 :) both thus 
containing a sali-molecule of metal, like the compound oxide of iron, which appears to be a 
condition of stability. 



430 TELLURIUM. 

might be procured in quantity if any useful application of the metal were dis- 
covered. It is a lead-gray mineral, having the metallic lustre, composed of 
flexible laminae, soft to the touch, and making a streak upon paper, like plum- 
bago. Nitric acid oxidates it easily, without dissolving it. Its density is from 
4.138 to 4.569. A ter sulphur et of molybdenum is obtained in the same way 
as the corresponding compound of tungsten, and affords crystallizable sulphur 
salts, which are red. The sulphomolybdate of sulphuret of potassium combines 
likewise with nitrate of potash. AVhen a solution of the former salt is boiled 
with tersulphuret of molybdenum in excess, the latter is converted into bi- 
sulphuret of molybdenum, and a quadrisufphuret of molybdenum, dissolves in 
combination with the sulphuret of potassium. The quadrisulphuret may be 
precipitated by hydrochloric acid, and when dried is a cinnamon-brown 
powder. 

Chlorides of molybdenum. — A profochloride is formed when molybdous ox- 
ide is dissolved in hydrochloric acid ; the bichloride when molybdenum is heated 
in dry chlorine gas, as a dark-red gas, which condenses in crystals, like those 
of iodine. It forms a crystallizable double salt with sal-ammoniac. The 
chloromolybdic acid, or compound of terchloridp of molybdenum and molybdic 
acid, Mod, CI orMoCl 3 4-2MoQ 3 , is formed with molybdic acid, when molybdic 
oxide is exposed to chlorine gas at a red heat. It sublimes under a red heat, 
and condenses in crystalline scales, which are white with a shade of yellow* 



SECTION VI. 

TELLURIUM. 

Eq. 801.8 or 64.25; Te. 

Tellurium is a metal of rare occurrence, and appeared at one time to be al- 
most confined to certain gold mines in Transylvania ; but it has been found 
lately, in. considerable abundance, at Schemnitz, in Hungary, combined with 
bismuth ; and in the silver mines of Sadovinski in the Altai, united with silver 
and with lead. It was first described as a new metal by Klaproth, who gave it 
the name tellurium, from tellua, the earth. Tellurium is separated from the 
foreign bodies with which it is mixed and combined in its ores, by processes of 
a very complicated nature. (Berzelius, Traite, I. 344.) 

In a state of purity, tellurium is silver-white and very brilliant. It is very 
crystallizable, assuming a rhombohedral form, in which it is isomorphous with 
arsenic and antimony. It is brittle, and an indifferent conductor of heat and 
electricity for a metal. Its density is from 6.2324 to 6.2578, according to 
Berzelius. Tellurium is about as fusible as antimony; at a higher temperature 
it may be distilled. It burns in air, at a high temperature, with a lively blue 
flame, green at the borders, and diffuses a dense white smoke, which gene- 
rally has the odour of decaying horse-radish, from the presence of a little se- 
lenium. Tellurium belongs to the sulphur class of elements. Like selenium 
and sulphur, it dissolves to a small extent in concentrated sulphuric acid, and 
communicates to it a fine purple-red colour. In this solution, the metal is not 
oxidated, for it is precipitated again, in the metallic state, by water. This metal 
has also considerable analogy with antimony, and may probably connect toge- 
ther the sulphur and phosphorus families. Tellurium combines in two pro- 
portions with oxygen, forming tellurous acid, Te0 2 , and telluric acid, Te0 3 . 

Tellurous acid, Te0 2 ; 1001.8 or 80.25.— This acid differs remarkably in 
properties according as it is anhydrous or hydrated, forming two isomeric 



TELLUROUS ACID. 431 

modifications of the same acid, of which the anhydrous acid has been named 
alphatellurous acid, and the hydrated betatellurous, by Berzelius, to whom we 
are indebted for nearly all our accurate knowledge of the acids of tellurium. 
But a sufficient distinction will be made between these bodies by retaining- one 
of these terms, alphatellurous, as applied to the anhydrous acid, and confining 
the term tellurous acid to the hydrated acid. The proper tellurous acid then 
is obtained by precipitating the bichloride of tellurium by cold water; or by 
fusing anhydrous tellurous acid with an equal weight of carbonate of potash, 
so long as carbonic acid is disengaged, dissolving the tellurite of potash in 
water, and adding nitric acid to it, till the liquor distinctly reddens litmus 
paper. A white and bulky precipitate is produced, which is washed with ice- 
cold water, and afterwards dried without artificial heat. Tellurium likewise 
dissolves with violence in pure nitric acid of density J .25, and if after the first 
five minutes, the clear liquid be poured into water, tellurous acid is precipi- 
tated, in white flocks. But if not immediately precipitated, the nitric acid so- 
lution undergoes a change. 

The hydrated acid obtained by these processes forms a light, white, earthy 
mass, of a bitter and metallic taste. It instantly reddens litmus paper, and 
while still humid, dissolves to a sensible extent in water. It is very soluble 
in acids, and these solutions are not subject to change, except that in nitric 
acid. Ammonia and the alkaline carbonates also dissolve it easily, the latter 
becoming bicarbonates. It is this tellurous acid which plays the part of acid 
in the tellurites, and also that of base in some compounds which the tellurous, 
like vanadic, tungstic, and molybdic acids, forms with the stronger acids. 
The tellurites of potash and soda, which are neutral in composition, are very 
soluble, and have a strong alkaline reaction; their solutions are decomposed by 
the carbonic acid of the air. 

Alphatelbtrous acid. — When the solution of tellurous acid in water is heated 
to 104°, it deposites alphatellurous acids in grains, and loses its acid reaction. 
The same change occurs when it is attempted to dry the hydrated tellurous 
acid by heat. It parts with combined water, and becomes granular. The solu- 
tion of tellurous acid in nitric acid changes spontaneously in a few hours, and 
in a quarter of an hour when heat is applied to it, and allows the alphatellurous 
acid to precipitate. When the deposition of the acid is slow, it forms a crys- 
talline mass of fine grains, among which octohedral crystals may be per- 
ceived by the microscope. The acid is then anhydrous. Alphatellurous acid 
does not redden litmus, or not till after a time. It is but very slightly soluble 
in water; the solution has no acid reaction. No salts of alphatellurous have 
been formed in the humid way, although from its analogy to a corresponding 
telluric acid, it is probable that such salts may exist. At a low red heat, it 
fuses into a clear transparent liquid of a deep yellow colour, which on cooling 
becomes a white and highly crystalline mass, easily detached from a crucible. 
Tellurous acid is volatile, although less so than the metal itself. 

Bitellurite of potash, KO,Te 2 4 , is obtained by fusing two atoms of tel- 
lurous acid with one atom of carbonate of potash. It appears to be capable of 
existing in a hot solution, and of crystallizing in certain circumstances; but it 
is decomposed by cold water, which resolves it into the neutral salt, which 
dissolves, and a qvadritellurite of potash, KO,Te 4 8 + 4HO. The latter salt 
cannot be redissolved again in water, without decomposition. In losing its 
water when heated, it swells up like borax. 

Telluric acid, Te0 3 ; 1101.8 or 88.25. — This acid is obtained in combina- 
tion with potash, on fusing tellurous acid with nitre. It may then be transferred 
to barytes, and the insoluble tellurate of barytes decomposed by sulphuric 
acid. The solution of telluric acid gives bulky hexagonal prismatic crystals. Its 
taste is not acid, but metallic, resembling that of nitrate of silver. Indeed, it 



432 TELLURIUM. 

appears to be a feeble acid, reddening litmus paper, although with difficulty, 
when the solution is diluted. The crystallized acid contains 3HO, of which 
it loses 2HO by efflorescence, a little above 212°. It thereafter appears inso- 
luble in cold water, but may be redissolved completely by long digestion, par- 
ticularly with ebullition, and is not permanently altered. Telluric affects the 
same multiples in its salts as tellurous acid. The neutral tellurate of potash 
is KO,Te0 3 -f5HO, bitellurate of potash, KO,Te 2 O s +4HO, quadritellurate of 
potash, KO,Te 4 12 -f4HO. All these salts may be obtained directly, in the 
humid way, by dissolving the proper proportions of hydrated acid and carbonate 
of potash together, in hot water. A portion of the combined water, in the 
last two salts, is unquestionably basic, but how much of it is so has not been 
determined. They cannot be made anhydrous by heat without being essen- 
tially altered in properties. 

Alphatelluric acid. — The crystals of hydrated telluric acid lose all their 
water at a heat under redness, and become a mass of a fine orange-yellow co- 
lour, without changing their form. This yellow matter, which is distinguished 
as alphatelluric acid by Berzelius, is remarkable for its indifference to chemical 
reagents, being completely insoluble in cold or boiling water, in hot hydro- 
chloric and nitric acids, and in potash ley. At a high temperature it is de- 
composed, losing oxygen, and leaving tellurous acid white and pulverulent. 
The salts of telluric acid are also converted into tellurites, at a red heat by the 
loss of oxygen. 

The neutral tellurate of potash undergoes no change in constitution under 
the influence of heat, resembling in that respect those tribasic phosphates, of 
which the whole three atoms of base are fixed. The bitellurate of potash 
loses its water and becomes yellow at a temperature under redness, and is 
changed in a quadritellurate, which is insoluble alike in water and dilute acids. 
Water dissolves out neutral tellurate from the yellow mass. The insoluble 
salt is named the alphaquadritellurate of potash, by Berzelius. The elements 
of this compound are united by a powerful affinity. It is formed when hy- 
drated telluric acid is mixed intimately with another potash salt, such as nitre 
or chloride of potassium, and the mixture calcined at a temperature which 
should be much inferior to a red heat; also when tellurous acid is ignited with 
chlorate of potash, and in other circumstances. Hydrate of potash dissolves 
the alphaquadritullurate by fusion, and nitric acid by a long-continued ebulli- 
tion; but in both cases the acid is found as ordinary telluric acid in solution. 

Telluretted hydrogen, TeH, is a gaseous compound of tellurium and hy- 
drogen, analogous in constitution and properties to sulphuretted hydrogen. It 
is obtained by fusing tellurium with zinc or with tin, and acting on the mixture 
by hydrochloric acid. 

Definite sulphurets of tellurium have been obtained, corresponding with 
tellurous and telluric acids. They are sulphur acids. 

Two chlorides of tellurium have been formed, a protochloride, TeCl, to 
which there is no corresponding oxide, and a bichloride, TeCl 2 . No higher 
chloride, corresponding with telluric acid, has been obtained. 



ARSENIC. 433 



ORDER VI. 



METALS ISOMORPHOUS WITH PHOSPHORU& 



SECTION I. 

ARSENIC. 
Eq. 940.1 or 75.34 (470.04 or 37.67, Berzelius and Turner,) As. 

This metal is found native, but more generally in combination with other 
metals, particularly cobalt and nickel, and is largely condensed, during the 
roasting of their ores, in the state of arsenious acid. The metal may be easily 
obtained, in a state of purity, by subliming a portion of native arsenic in a 
glass tube or retort, by the heat of a lamp, or by reducing a mixture of one part 
of arsenious acid and three parts of black flux, in the same apparatus. The 
metal forms a crust, in condensing, of a steel-gray colour and bright metallic 
lustre. It has been observed to crystallize by sublimation in rhombohedral 
crystals, and is isomorphous with tellurium and antimony. It is a brittle 
metal, and very easily pulverized. The density of arsenic is from 5.7 to 5.96. 
It arises in vapour at 356° (180° Cent.) without first undergoing fusion. Ar- 
senic vapour is colourless; its density is 10.370; and, like phosphorus and 
oxygen, its combining measure is one volume. It has as strong an efi'ect upon 
the organ of smell as selenium: its odour resembles that of garlic. Arsenic 
combines in three proportions with oxygen, forming a gray suboxide by spon- 
taneous oxidation in air, of which the composition is undetermined, With 
arsenious and arsenic acids, As0 3 and As0 5 . 

Arsenious acid, As0 3 ; 1240.1 or 99.34. — This compound is also known 
as white oxide of arsenic, and is an abundant mercantile product. It is in 
vitreous masses, as obtained by sublimation, which immediately after subli- 
mation are transparent and colourless, or have a delicate shade of yellow, but 
gradually become white and opaque, (page 126.) The density of the vitreous 
acid is 3.7385, of the opaque acid, 3.699. Arsenious acid sublimes at 380°, 
without softening or fusing, forming a vapour which is colourless and with- 
out odour. The density of this vapour is about 13.000 (Mitscherlich;) one 
volume of arsenious acid vapour, or the combining measure, contains accord- 
ingly, one volume of arsenic vapour and three volumes of oxygen gas. When 
slowly sublimed in a glass tube, it is always obtained in distinct transparent 
crystals of adamantine lustre, which are regular octohedrons. But arsenious 
acid is dimorphous, and occurs sometimes, in the roasting of arsenical ores, 
in thin, flexible prisms, of a pearly lustre, of which the form does not belong 
to the regular system, (Wohler.) Arsenious acid dissolves very slowly in 
37 



434 ARSENIC. 

water, and the prismatic crystals in particular require to be heated with it for 
a long time. A concentrated solution prepared in this way may afterwards 
be cooled without arsenious acid immediately crystallizing from it. One hun- 
dred parts of boiling water dissolve 9.68 parts of the vitreous acid, and 11.47 
parts of the opaque acid; and when the solutions cool to 60°, 1.78 parts remain 
in the first* and 2.9 parts in the latter; the first reddens litmus paper, the 
second makes it blue, although feebly, if already red. When the vitreous acid 
in powder, is covered with ammonia, it heats a little; no combination of the 
acid with ammonia takes place, for the latter may be completely removed by 
water, but the w r ashed powder is found to have passed into the condition of 
the opaque acid. For these curious facts we are indebted to M. Guibourt. 
The taste of powdered arsenious acid is scarcely perceptible, but it is slightly 
sweet, and leaves a feeling of acridity in the mouth. 

Arsenious acid dissolves in the solutions of many acids, particularly hydro- 
chloric acid, to a greater extent than in water, but without combining with 
these acids. It is dissolved, however, by the bitartrate of potash, with the 
formation of a crystallizable salt, analogous to the potash-tartrate of antimony. 
Arsenious acid is dissolved by potash, soda, and ammonia; but the salts which 
it forms with these bases do not crystallize. It is also dissolved by alkaline 
carbonates, but is sometimes deposited from these solutions in a free state; so 
that it is doubtful whether arsenious acid displaces carbonic acid in the humid 
way. The arsenites of the earths and metallic oxides are insoluble in water, 
but soluble in acids; these precipitated arsenites usually carry down an excess 
of arsenious acid, and are not easily obtained in a definite state. 

Jlrsenic acid, AsO s , 1440.1 or 115.34. — This acid is obtained by heating 
powdered arsenious acid in a basin, with an equal quantity of water, and 
adding to the mixture at the boiling point nitric acid in small quantities, so 
long as ruddy fumes escape. An addition of hydrochloric acid to the water 
is generally made, to increase the solubility of the arsenious acid, but it is not 
absolutely necessar)^. The solution of arsenic acid is then evaporated to dry- 
ness, to expel the remaining nitric and hydrochloric acids, but the dry mass 
is not heated above the melting point of lead, otherwise oxygen gas is emitted 
and arsenious acid reproduced. Arsenic acid, thus obtained, is milk-white, 
and contains no water. Exposed to air, it slowly deliquesces, and runs into 
a liquid. But notwithstanding this, when strongly dried, it does not dissolve 
completely in water at once, and a portion of it appears to be insoluble; but 
the whole is dissolved by continued digestion. Arsenic acid, in absorbing 
moisture from the air, sometimes forms hydrated crystals, which are highly 
deliquescent; but this acid is easily made anhydrous, and does not retain basic 
water with force, like phosphoric acid. Its solution has a sour taste, and red- 
dens vegetable blues. Arsenic acid, indeed, is a strong acid, and expels, with 
the aid of heat, all the volatile acids from their combinations. Arsenic acid 
undergoes fusion at a red heat, and is completely dissipated in arsenious acid 
and oxygen at a higher temperature. 

When an equivalent of arsenic acid is ignited with an excess of carbonate of 
soda, three equivalents of carbonic acid are expelled, and a tribasic arseniate 
of soda formed, w T hich crystallizes when dissolved in water, with 24 equiva- 
lents of water, forming the salt 3NaO,As0 5 -f 24HO, isomorphous with the sub- 
phosphate of soda. The same salt is obtained by treating arsenic acid in 
solution, with an excess of caustic soda. When carbonate of soda is added to 
a hot solution of arsenic acid, so long as there is effervescence, a salt is obtained 
by evaporation, corresponding with the common phosphate of soda, containing 
2 eq. of soda and 1 eq. of water as bases. This salt affects the same two mul- 
tiples, in its water of crystallization, as phosphate of soda, namely 24HO and 
1 4HO, but most frequently assumes the smaller proportion, forming the salt 



ARSENIETTED HYDROGEN. 435 

2NaO,HO,AsO s -M4HO. This arseniate is more soluble than the phosphate, 
and slightly deliquescent in damp air. When to the last salt a quantity of 
arsenic acid is added, equal to what it already contains, and the solution is 
highly concentrated, the salt named binarseniate of soda crystallizes at a low 
temperature. This salt contains 1 eq. of soda, and 2 eq. of water as bases, 
with 2 eq. of water of crystallization, and corresponds with the biphosphate of 
soda. Its formula is NaO,2HO,As0 5 -f2HO. The binarseniate of potash, 
which is analogous in composition, is a highly crystallizable salt. It is some- 
times prepared by deflagrating arsenious acid, with an equal weight of nitrate 
of potash. These arseniates of the alkalies, which contain water as base, all 
lose that element at a red heat, but unlike the phosphates they recover it, when 
again dissolved in water, Arsenic acid, therefore, forms only one, and that a 
tribasic class of salts. The arseniates of earths and other metallic oxides are 
insoluble in water, but soluble in acids. The arseniate of silver (3AgO,As0 5 ) 
falls as a precipitate, of a chocolate brown colour, when nitrate of silver is 
added to the solution of an arseniate, and affords an indication of the presence 
of arsenic acid. 

Sulphurets of arsenic. — When the following sulphuret, realgar, is digested 
in caustic potash, it loses sulphur and leaves a brownish black powder, having 
some resemblance to peroxide of lead, which is the sulphuret SAs 6 , according 
to Berzelius. Bisulphuret of arsenic, AsS 2 , is obtained by fusing sulphur 
w r ith an excess of arsenic or arsenious acid. It is transparent and of a fine 
ruby colour after cooling, and may be distilled without decomposition. It forms 
the crystalline mineral realgar. Sulpharsenious acid or orpiment, AsS 3 , also 
occurs native. It may be prepared by decomposing a solution of arsenious 
acid in hydrochloric acid, by sulphuretted hydrogen, or by an alkaline sulphuret. 
This sulphuret has a rich yellow colour, and is the basis of the pigment king's 
yellow. It is insoluble in acids, but is soluble to a small extent in water, con- 
taining sulphuretted hydrogen, and also in pure water, but is precipitated by 
ebullition with a little hydrochloric acid. When heated it fuses readily, and 
becomes crystalline on cooling. It is readily dissolved by ammonia and solu- 
tions of the fixed alkalies, and is indeed a powerful sulphur acid. Sulpharsenic 
acid, AsS 5 , falls as a yellow precipitate, having very much the appearance of 
orpiment, when a solution of arsenic acid, somewhat concentrated, is decom- 
posed by sulphuretted hydrogen. It maybe sublimed without change; and 
gives a mass after cooling, which is not crystalline. 

Chlorides of arsenic. — A terchloride, AsCl 3 , coresponding with arsenious 
acid, is formed when arsenic is introduced into chlorine gas, in which it takes 
tire and burns spontaneously. The same compound is obtained by distilling 
a mixture of 1 part of arsenic, with 6 parts of corrosive sublimate, as a colour- 
less, oily, and very dense liquid. It is resolved by water into arsenious and 
hydrochloric acids. A lower chloride of arsenic appears to be formed when a 
mixture of arsenic and calomel is distilled;' it is obtained as a dark-brown sub- 
limate, mixed with calomel. No chloride corresponding with arsenic acid is 
known. The bromide of arsenic, AsBr 3 , is formed by the direct combination 
of its elements. The iodide of arsenic, Asl 3 , is formed, according to Plisson, 
by digesting 3 parts of arsenic with 10 of iodine, and 100 of water, so long as 
the odour of iodine is perceived. The liquid yields by evaporation red crys- 
tals of the iodide. The fluoride of arsenic is obtained by the distillation of a 
mixture of fluor spar and arsenious acid with sulphuric acid. It is a fumino- 
colourless liquid; the density of its vapour is 2730 (Unverdorben.) 

Arsenic and hydrogen. — A solid arseniuret of hydrogen was obtained, bv 
Davy, by using metallic arsenic as the negative pole (the chloroid,) in de- 
composing water. Gay-Lussac and Thenard have also shown that the same 
compound precipitates, when arseniuret of potassium is dissolved in water. 



436 ' ARSENIC. 

It is a chestnut-brown powder, which may be dried without change. Its 
composition is not certainly determined. Arsenietted hydrogen, AsH 3 , a gas 
analogous in constitution to ammonia, is obtained by dissolving an alloy of equal 
parts of zinc and arsenic in sulphuric acid, diluted with three times its weight 
of water. It is a dangerous poison, when inhaled even in the most minute 
quantity, and should, therefore, be prepared with the greatest caution. The 
density of this gas is 2695, according to M. Dumas. It is liquefied by a cold 
of — 40°. When passed through a glass tube, heated to redness by a spirit 
lamp, this gas is decomposed and deposites metallic arsenic. The flame of this 
gas, when burned in air, also deposites metallic arsenic upon a cold ob- 
ject exposed to it. No combination of arsenietted hydrogen is known with 
either acids or bases. It precipitates many of the metallic solutions, which are 
precipitated by sulphuretted hydrogen, but not oxide of lead; its hydrogen 
alone being oxidated by the common metallic oxides, and the arsenic precipi- 
tating in combination with the metal. This gas, when pure, is completely 
absorbed by a solution of sulphate of copper, and AsCu 3 precipitated. 



TESTING FOR ARSENIC. 

Poisoning from arsenious acid is greatly more frequent than from any other 
substance. Hence, a more than usual degree of importance is attached to the 
modes of detecting the presence of arsenic in minute quantity. Of the diffe- 
rent preparations of the metal, arsenic acid, and after it arsenious acid, are the 
most poisonous; the salts and sulphurets are so to a much less degree. Ar- 
senious acid in the solid form and unmixed with foreign matters, is easily re- 
cognised as a white heavy powder, which is tasteless or nearly so, is entirely 
volatile by heat, and diffuses a garlic odour in the reducing flame of a lamp. 
When in solution in water, arsenious acid may be detected by fluid tests, of 
which the three following are the most important. 

Fig' 107 ** ^ u h^ lurettec ^ hydrogen gas, made to pass in a stream 

through a solution of arsenious acid, (fig. 107,) produces a 
precipitate of orpiment, or a golden yellow solution if the 
quantity of arsenic be very small. In this experiment, the 
liquid should always be slightly acidulated with hydro- 
chloric or nitric acid, and also be boiled, afterwards, to com- 
plete the precipitation of the sulphuret. 

2. Ammonio-nitrate of silver, is an exceedingly delicate 
test of arsenious acid, whether free, or in combination with 
an alkali. This reagent is prepared by adding diluted am- 
monia to a solution of nitrate of silver, till the oxide of silver, 
which is first thrown down, is again redissolved. When the 
ammonia has been added in proper quantity and not in excess, the odour of 
that substance is scarcely perceptible, and the liquid contains in solution the 
crystallizable ammonio-nitrate of silver, AgO,N0 5 -f 2NH V This test 
liquid throws down from arsenious acid, the yellow arsenite of silver, which 
is redissolved both by acids and ammonia. A solution of nitrate of silver' 
gives the same indication, as the prepared ammonia-nitrate, in an alkaline, but 
not in an acid solution of arsenious acid. Nitrate of silver produces a yellow 
precipitate of phosphate of silver, in phosphate of soda or any other soluble 
phosphate, of the same colour as the arsenite of silver, and which might, 
therefore, be mistaken for the latter. But the action of the ammonio-nitrate 
is not liable to that ambiguity, as it does not produce a yellow precipitate in an 
alkaline solution of phosphoric acid; the phosphate of silver being then re- 
tained in solution by the ammonia of the reagent, although arsenite of silver 




TESTING FOR ARSENIC. - 437 

is precipitated in the same circumstances. Both phosphate and arseniate of 
silver are indeed considerably more soluble in ammonia, than the arsenite of 
the same metal. 

Ammonio-sulphate of copper, gives a beautiful green precipitate, the arsenite 
of copper, in both alkaline and acid solutions of arsenious acid; sulphate of 
copper gives the same precipitate in the former, but not in the latter. 

But in solutions containing organic matter, the indications of these tests are 
sometimes delusive, and often doubtful, particularly the indications of the latter 
two- Recourse is then had to the proper means of obtaining arsenic in the 
metallic form, in which it cannot be mistaken, from the liquid suspected to 
contain arsenious acid. Indeed, even where the indications of the fluid tests 
are clear, the reduction tests should never be omitted, the evidence which it 
affords being of a superior and completely demonstrative character. The re- 
duction test of arsenic is practised in two different waysi (1) by the reduction 
of the sulphuret of arsenic by means of charcoal and carbonate of potash, and 
(2) by the production, and subsequent decomposition of the gaseous compound 
of arsenic and hydrogen. The following operations are necessary in the prac- 
tice of the first method: 



REDUCTION TEST OF ARSENIC. 

I. Preparation of the fluid: 

1. Boil the matters with water add a k\v drops of nitric acid. 

2. Strain through calico. 

3. Precipitate animal matter by an excess of nitrate of silver, and subse- 

quent addition of common salt. 

4. Filter through paper. 

II. Precipitation of the sulphuret of arsenic: 

1. Transmit a stream of sulphuretted hydrogen through the liquid for 

half an hour. 

2. Heat the liquid in an open vessel for a few minutes, to cause the pre- 

cipitate to separate. 

3. Wash the precipitate by affusion of water acidulated with hydrochloric 

acid, and subsidence. 

4. Dry the precipitate at a temperature not exceeding 300°. 

III. Reduction of the sulphuret of arsenic: 

1. Mix the dried precipitate intimately with twice its bulk of dry black 

flux (carbonate of potash and charcoal,) and heat to redness in a glass 
tube of the form and and size of a or 6, (see fig. 109.*) 

2. Heat slowly a particle of the metallic crust in a glass tube c, and ob- 

serve the formation of a white crystalline sublimate of arsenious 
acid. 



Fig. 108. 



* [When the quantity is small, the reduction tube of 
Berzelius (fig. 108,) is to be preferred. It may be readily 
formed by heating the tube a (fig. 109) in a spirit lamp until 
soft, and then drawing out the softened part to the proper di- 
mensions. R. B.l 



37* 





438 



ARSENIC. 
Fig. 109. 



( 


a 








v s — s 


«•—"' 


c 



Hydrogen cannot be evolved in contact with a soluble or insoluble prepara- 
tion of arsenic, without combining with the metal, which is thus removed from 
the liquor, in the form of arsenietted hydrogen gas. Mr. Marsh has founded, 
upon that fact, a simple and elegant mode of obtaining metallic arsenic from 
arsenical liquors. The stopcock being removed from the bulbed apparatus re- 
presented in the figure, a fragment of zinc is placed in the 
Fig. 110. lower bulb, and diluted sulphuric poured upon it. The 
stopcock being replaced and closed, the lower bulb is soon 
filled with hydrogen gas, and the acid liquid forced into the 
upper bulb. It is necessary to test this hydrogen for ar- 
senic, which will be found in it, if the zinc itself contains 
that metal. The gas for this purpose is kindled at the stop- 
cock and allowed to burn with a small flame. If a stone- 
ware plate be depressed upon the flame, a black spot of a 
steel-gray colour and bright metallic lustre, is formed upon 
the surface of the plate, in a few seconds, supposing the 
gas to contain arsenic, or if a cold object of glass be held 
over the flame, at a small height above it, a white sublimate 
of arsenious acid condenses upon the glass. But if the 
zinc employed contains no arsenic, neither of these effects 
is produced. The zinc being proved to be free from ar- 
senic, a portion of the liquor to be tested, is introduced 
into the lower bulb, in addition to the acid and zinc already there; and when 
the bulb comes again to be filled with hydrogen gas, the latter is burned and 

examined precisely as before. If the li- 
Fig. 111. quor is loaded with organic matter, as ge- 

nerally happens with the liquids sub- 

mitted to examination in actual cases of 
poisoning, the gas may be filled with froth, 
and the evolution of it very slow. But in 
the course of a night, the gas is generally 
obtained in sufficient quantity, and in a 
proper state, to permit of an examination 
of it. Where the gas is evolved freely 
and without frothing of the liquid, a plain 
bottle with a cork and glass jet will be 
sufficient for this reduction experiment. 
Then also instead of burning the gas at the 
jet, it may be allowed to escape by a hori- 
zontal tube, such as that in the figure, a portion of which is heated to redness, 
by a spirit lamp; the arsenic condenses within the tube, beyond the flame and 
nearer the aperture, and forms a metallic crust. Or the extremity of this tube 





REDUCTION TEST OF ARSENIC. 439 

may be allowed to dip in a solution of nitrate of silver, by which the arsenietted 
hydrogen is condensed, and a black bulky precipitate of arseniuret of silver 
formed. This precipitate, when dried and heated in a glass tube, affords a 
white sublimate of aisenious acid, which may afterwards be dissolved by boil- 
ing in a small quantity of distilled water, containing a single drop of ammo- 
nia, and the solution tested for arsenious acid by nitrate of silver and sulphate 
of copper. (Liebig, Clark.) 

When the liquid examined contains antimony, that metal combines with the 
nascent hydrogen, and comes off as antimonietted hydrogen, a gas which 
when burned, or when heated in a glass tube, gives the metal and a white sub- 
limate, in the same circumstances as arsenic, (L. Thompson.) Antimony, 
however, may be recognized by a peculiarity of its reduction in the ignited 
tube. This metal is deposited in the tube, on both sides of the heated portion 
of it, and closer to the flame than arsenic, owing to the less volatility of anti- 
mony. The white sublimate also, if dissolved in water, containing a drop of 
ammonia, will not give the proper indications with the fluid tests of arsenic, if 
the metal is antimony. 

Antidote to arsenious acid. — When hydrated peroxide of iron is mixed with 
a solution of arsenious acid to the consistence of a thin paste, a reaction oc- 
curs by which the arsenious acid disappears in a few minutes, and the mass 
ceases to be poisonous. The arsenious acid derives oxygen from the peroxide 
of iron, and becomes arsenic acid, while the peroxide of iron becomes pro- 
toxide, a protarseniate of iron being the result, which is insoluble and inert: 

2Fe 2 3 and As0 3 = 4FeO-f As0 5 . 

The constitution of this arsenite of iron is probably 2FeO,HO,As0 5 -f 2FeO. 
Peroxide of iron when used as an antidote to arsenious acid, should be in a 
gelatinous state as it is obtained by precipitation, without drying. It may be 
prepared extemporaneously, by adding bicarbonate of soda in excess to any 
tincture, or red solution of iron. 



SECTION II. 

ANTIMONY. 
Eq. 1612.9 or 129.24; (806.4 or 64.62 Berzelius and Turner;) Sb {stibium.) 

This metal was well known to the alchemists, and is one of the metals of 
which the preparations were first introduced into medicine. Its sulphuret is not 
an uncommon mineral, and is the source from which the metal and its compounds 
are always derived. 

The sulphuret of antimony is easily reduced to the metallic state by mixing 
together 4 parts of that substance, 3 parts of crude tartar and 1 h parts of nitre, 
and projecting the mixture by small quantities at a time into a red hot crucible. 
The sulphuret is also sometimes reduced by fusion with small iron nails, which 
combine with t&e sulphur and disengage the antimony. Or it may be obtained 
in a state of greater purity, by igniting strongly in a crucible, a quantity of the 
potash-tartrate of antimony and placing the metallic mass obtained, in water to 
remove any potassium it may have acquired. Antimony is a white and 
brilliant metal, generally possessing a highly lamellated structure. It is 
easily obtained in rhombohedral crystals of the same form as arsenic and 
tellurium. Its density is from 6.702 to 6.86. It undergoes no change in the 



440 ANTIMONY. 

air. The point of fusion of antimony is estimated at 797°; it may be distilled 
at a white heat. This metal burns in air at a red heat, and produces copious 
fumes of oxide of antimony. Antimony combines in three proportions with 
oxygen, forming oxide of antimony and antimonic acid, Sb0 3 and Sb0 5 , which 
correspond respectively with arsenious and arsenic acids, and antimonious acid 
Sb0 4 , which is probably an intermediate or compound oxide, analogous to the 
black oxide of iron. 

Oxide of antimony, Sb0 3 , 1912.9 or 153.28. — Oxide of antimony may be 
obtained by dissolving the sulphuret finely pounded, and in the condition in 
which it is known as prepared sulphuret of antimony, in four times its weight 
of concentrated hydrochloric acid. Pure sulphuretted hydrogen comes off, and 
the antimony is converted into terchloride (SbS 3 and 3HC1 = SbCl s and 3HS.) 
The clear solution may be poured off,f and precipitated at the boiling point 
by a solution of carbonate of potash, added in excess; the carbonic acid, which 
does not combine with oxide of antimony, escapes as gas. Oxide of antimony 
so prepared, is anhydrous, but is slightly soluble in water; it is white but as- 
sumes a yellow tint when heated. It is fusible at a red heat, and sublimes at a 
high temperature in a close vessel, where it cannot pass into a higher state of 
oxidation. The brilliant crystalline needles which condense about antimony in 
a state of combustion are likewise this oxide. They possess the unusual pris- 
matic form of arsenious acid observed by Wohler. Oxide of antimony also 
crystallizes as frequently in regular octohedrons, the other form of arsenious 
acid. It occurs in the prismatic form, as a rare mineral, of which the density 
is 5.227. 

When a solution of potash is poured upon the bulky hydrate of oxide of anti- 
mony, which is precipitated from the chloride by water, a portion of the oxide 
is dissolved, but the greater part loses its water, and is reduced in a few seconds 
to a fine grayish, crystalline powder, which is a neutral combination of the ox- 
ide of antimony with potash. Oxide of antimony enters into other salts as a 
base. 

Sulphuret of antimony, SbS 3 , 2216.4 or 177.6. — The common ore of anti- 
mony is a tersulphuret, SbS 3 , corresponding with the preceding oxide of anti- 
mony. It is rarely free from sulphuret of arsenic which thus often enters the 
antimonial preparations derived from the sulphuret of antimony, but into tartar 
emetic less frequently than the others. The same sulphuret is formed when 
salts of the oxide of antimony, such as tartar emetic, are precipitated by sul- 
phuretted hydrogen, but it is then of an orange-red colour. When the pre- 
cipitated sulphuret is dried, it loses water and becomes anhydrous, still remain- 
ing of a dull orange colour; but heated more strongly, it shrinks at a particular 
temperature and assumes the black colour and metallic lustre of the native sul- 
phuret. This sulphuret is also obtained of a dark-brown colour by boiling the 
prepared sulphuret of antimony in a solution of carbonate of potash, and allow- 
ing the solution to cool; by fusing 2| parts of the prepared sulphuret with 1 
part of carbonate of potash, or dissolving it in a boiling solution of caustic pot- 
ash, and afterwards adding an acid. This preparation is known as Kermes 
mineral. It has a much duller colour than the precipitated sulphuret, but differs 
from it only in containing a small quantity of an alkaline sulphuret, which can- 
not be removed by washing (Berzelius.) When the sulphuretjof antimony is 
oxidated at a red heat, much sulphur is burned off, and an impure oxide of anti- 
mony remains. This matter forms, when fused, the glass of antimony, which 
contains a considerable quantity of undecomposed sulphuret. The glass reduced 
to powder is boiled with bitartrate of potash, as a source of oxide of antimony, 
in the pharmaceutical preparation of tartar emetic. The oxide of antimony is 
dissolved out from the glass by acids, and a substance is left which is called 
saffron of antimony. This last is a definite compound of oxide and sulphuret 



SALTS OF ANTIMONY. 441 

of antimony Sb0 3 -f 2SbS 3 , which also occurs as a mineral, namely red- anti- 
mony ore. 

Chloride of antimony, SbCl 3 , is obtained by distilling either metallic anti- 
mony or the sulphuret of antimony with corrosive sublimate. When heated it 
flows like an oil, and becomes a crystalline mass on cooling. It is a powerful 
cautery. This salt deliquesces in air, and is troubled, owing to the deposition 
of a subsalt. A concentrated solution of chloride of antimony is also obtained 
by dissolving the sulphuret of antimony in hydrochloric acid. When this solu- 
tion is thrown into water, it gives a white, bulky precipitate, which after a time 
resolves itself into groups of small crystals, having usually a fawn colour; it 
was formerly called the powder of Jllgarotk. These small crystals are an 
oxichloride of antimony, of which the composition is 2SbCJ 3 -f 9Sb0 3 , accord- 
ing to the analysis of Johnston and Malaguti. 

Sulphate of antimony, Sb0 3 ,3S0 3 , is obtained by boiling metallic antimony 
with concentrated sulphuric acid, as a white saline mass, which is decomposed 
by water. 

Oxalate of potash and antimony, KO,C 2 3 -f Sb0 3 .3C 2 3 . — This is a 
double crystallizable salt of antimony, which, like the tartrate of potash and 
antimony, may be dissolved in water without decomposition. It is prepared 
by saturating binoxalate of potash with oxide of antimony. It is soluble, at 
48°, in ten times its weight of water, (Lassaigne.) According to Bussy, when 
binoxalate of potash is digested upon oxide of antimony in excess, two salts 
are formed, one in oblique prisms, and another less soluble, in intricate small 
crystals; but neither is very stable. The former is decomposed by much 
water: its analysis gave 3(K0,C o 3 ) + Sb0 3 ,3C,0 3 +6H0* 

Tartrate of potash aad antimony, KO.SbO 3 +(C,H l O 10 )2HO; 4164.2 -f 
225 or 333.68 + 18. — This salt, the tartar emetic or potash tartrate of antimony 
of pharmacy, is prepared by neutralizing bitartrate of potash with oxide of anti- 
mony ; the oxide obtained by decomposing the chloride or sulphate of antimony 
with water answers best for the purpose. A quantity of oxide of antimony 
may be boiled with three or four times its weight of water, and bitartrate of 
potash added in small quantities till the oxide is entirely dissolved. The filtered 
solution yields the salt, on cooling, in large transparent crys- F n ~ 
tals, of which the form is an octohedron with a rhombic base ; 
they become white in the air, and lose their water of crys- 
tallization. They are soluble in 14 times their weight of 
cold water, and in 1.88 boiling water, but not in alcohol. 
The mother liquor of these crystals becomes a syrupy liquid, 
and dries up into a gummy mass without crystallizing, when 
oxide of antimony has been dissolved in excess by the acid 
tartrate, in preparing the salt. Oxide of antimony is precipi- 
tated by potash or ammonia from a solution of this salt, when 
concentrated, but not when diluted, owing to the solubility of 
oxide of antimony in alkalies. Salts of the earths and basic 
metallic oxides, such as barytes and oxides of silver, throw 
down from its solution a compound of the tartrate of antimony, with tartrate of 
barytes, tartrate of silver, &c. (Wallquist.) Strong acids decompose the salt, 
and produce a precipitate which is a mixture of bitartrate of potash with oxide 
of antimony, or with a subsalt of that oxide. Sulphuretted hydrogen gas 
throws down the orange-red sulphuret of antimony from a solution of the tar- 
trate, and this precipitate affords the most conclusive indication of the presence 
of antimony. The orange precipitate should be collected, dried, and dissolved 




* Journal de Pharm. 1838, p. 509. 



442 



ANTIMONY. 



by heat in a few drops of concentrated hydrochloric acid. When the acid 
solution is dropped into a glass of water, the white and bulky hydrated oxichlo- 
ride of antimony precipitates. 

This salt was formerly described as a double tartrate of potash and antimony, 
or, abstracting its water of crystallization, which is differently stated at 2 and 
3 equivalents, as KO,(C 4 H 2 5 ) + Sb0 3 ,(C 4 H 2 5 .) When the atomic weight 
of tartaric acid is doubled, and it is represented as a bibasic acid, the formula 
for dry tartar emetic becomes KO.Sb0 3 , (C 8 H 4 O 10 .) In comparing the last 
formula with that of bitartrate of potash, represented also as a bibasic salt, 
KO.HO,(C 8 H 4 O 10 ,) it is observed that 1 eq. of oxide of antimony takes the 
place of 1 eq. of water, as base, although the former contains three eq. of oxy- 
gen and the latter only one. Tartrate of potash and antimony is, in this respect, 
an anomalous salt. Another equally remarkable fact respecting this salt has 
been observed by M. Dumas, namely, that 2 eq. of water are separated from 
the anhydrous salt at 428°, leaving a substance of which the elements are, 
C 8 H 2 O l2 SbK. The first part of this formula C 8 H 2 12 , M. Dumas looks upon 
as a quidribasic salt-radical existing in the tartrates, which in hydrated tartaric 
acid is united with 4H, in bitartrate of potash with 3H+K, and in tartrate of 
antimony and potash with Sb-f-K. Here Sb is found equivalent to, and capa- 
ble of, replacing 3H, (note p. 379.) Tartrate of antimony and potash would, 
therefore, fall to be represented by KSb, (C 8 H 2 12 )+2HO+ water of crystal- 
lization. 

Antimonious acid, Sb0 4 , is obtained by oxidating metallic antimony by 
nitric acid, or by roasting the sulphuret of antimony. It is the state of oxida- 
tion into which both oxide of antimony and antimonic acid pass, when 
ignited in open air. Antimonious acid is infusible and fixed, and is reduced 
to the metallic state with much greater difficulty than oxide of antimony. 
Fused with potash and separated afterwards from the alkali by an acid, it is 
obtained as a hydrate, containing 1 eq. of water, and having an acid reaction, 
Sb0 4 -f HO. It may also be viewed as a compound of antimonic acid with 
oxide of antimony. 

When hydrated antimonious acid is digested in hydrochloric acid, a solu- 
tion is obtained which is supposed to contain a corresponding chloride of 
antimony SbCl 4 . A corresponding sulphuret of antimony has also been 
formed. 

Antimonic acid, Sb0 5 , is most easily prepared by the oxidation of oxide of 
antimony, by nitric acid, as arsenic acid is prepared from arsenious acid. The 
excess of nitric acid should then be expelled by a heat short of redness. An- 
timonic acid is a pale yellow powder, tasteless and insoluble in water. It 
displaces carbonic acid from the alkaline carbonates, and combines with the 
alkali. It is also soluble in a boiling solution of potash, from which acids 
precipitate hydrated antimonic acid as a white powder. In the hydrated 
state antimonic acid is soluble in hydrochloric acid, and also in solutions of 
the alkalies, without heat. Antimoniate of soda is uncrystallizable. Anti- 
moniate of potash is prepared by deflagrating a mixture of 1 part of antimony, 
or of sulphuret of antimony, and 6 parts of nitre. The mass is first digested 
in cold water, which dissolves out nitrate and nitrite of potash, and leaves 
antimoniate of potash. When this residue is digested in boiling water, a binan- 
timoniate of potash is left, and the neutral antimoniate dissolved out. The 
solution is feebly alkaline; when concentrated to the consistence of honey, it 
gives crystalline grains. All acids, even the carbonic, occasion a precipitate 
in this solution, which is the biantimoniate of potash, KO,Sb 2 O 10 . When 
a soluble salt of lime or, of zinc is treated, at the boiling point, with the solu- 
tion of the neutral antimoniate of potash, the antimoniate of lime or of zinc 
separates in a crystalline state; other salts of antimonic acid fall as an insoluble 



URANIUM. 443 

powder, when solutions of the different metallic oxides are precipitated by 
the neutral salt. Many of the metallic antimoniates, particularly those of 
cobalt and copper, lose first their combined water when heated, and after- 
wards glow strongly when heated to redness. After that change, these 
antimoniates are not soluble either in acids or alkalies. 

Sulphaniimonic acid, SbS 5 , is obtained when antimonic acid or the follow- 
ing chloride of antimony is precipitated by sulphuretted hydrogen. It is of a 
much paler red colour than the other sulphurets of antimony, and constitutes 
the golden sulpharet of antimony of several pharmacopeias. 

Pentachloride of antimony, SbCl 5 , is formed when metallic antimony in 
powder is gently heated in chlorine gas. The antimony burns with scintil- 
lations, and a colourless or slightly yellow-coloured liquid distils over. This 
chloride condenses olefiant gas as readily as chlorine, and forms the Dutch 
liquid, the pentachloride being reduced at the same time to terchloride of 
antimony. 



ORDER V. 



METALS NOT INCLUDED IN TF1E FOREGOING CLASSES, OF WHICH THE 
OXIDES ARE NOT REDUCED BY HEAT ALONE. 

URANIUM. LANTANUM. 

CERIUM. TANTALUM. 

URANIUM. 

£o. 2711.4, or 217.26; U. 
• 

This metal is derived from the mineral pitchblende, which consists prin- 
cipally of protoxide of uranium. The mineral is dissolved in aqua regia, and 
a stream of sulphuretted hydrogen passed through the liquor, by which cop- 
per, lead and arsenic are precipitated. The liquid is afterwards boiled, and 
the protoxide of iron peroxidized by means of nitric acid. An excess of am- 
monia is then added to the liquid, and the precipitate formed of oxides of 
uranium, iron, cobalt and zinc, is washed, then treated with a dilute solution 
of carbonate of ammonia, which leaves the peroxide of iron, and dissolves the 
other oxides. By boiling the yellow solution, the carbonate of ammonia is 
expelled, and the oxides precipitate. These are dried and ignited, by which 
protoxide of uranium is rendered insoluble in acids. The other oxides are 
dissolved out of the ignited mass by hydrochloric acid, the protoxide of 
uranium remaining as a very fine, dark-gray powder, which is received on a 
filter and washed well. Protoxide of uranium, obtained in this manner, may 
be dissolved, with the aid of heat, in concentrated sulphuric acid. 

The peroxide of uranium is easily reduced by hydrogen. Arfwedson ob- 
tained the metal by passing hydrogen over the double chloride of uranium and 
potassium at a red heat, in the form of little regular octohedrons of a brilliant 
metallic lustre, and of a dark-gray colour, almost black. The density of this 
metal is 9.00. It combines with oxygen in two proportions, forming a pro- 
toxide, UO, and peroxide U 2 3 . 

Protoxide of uranium, Uranous oxide, UO, 2811.4 or 225.26. — This oxide 



444 URANIUM. 

is obtained when an alkali is added to a solution of any of its salts, as a green- 
ish-gray hydrate, which soon becomes yellowish, and is finally converted into 
uranic oxide by the oxygen of the air. Carbonate of ammonia added in excess 
to a uranous salt, redissolves the precipitate and forms a green solution. The 
uranous chloride, UC1, forms a green syrupy solution which does not crystal- - 
lize. The uranous sulphate yields, by evaporation, green prismatic crystals. 
This oxide is employed in painting upon porcelain, and yields a black of the 
greatest purity.* 

Peroxide of uranium, Uranic oxide, U 2 3 , 2911.4 or 233.26. — When an 
alkali is added to a salt of this oxide, a compound of uranic oxide and the 
alkali is precipitated and not the hydrated oxide itself; but the latter may be 
obtained by the oxidation of uranous oxide. The uranic hydrate is of a yellow 
colour, has an acid reaction upon litmus, and is decomposed by heat, allowing 
water and oxygen to escape, while uranous oxide remains. . Uranic oxide 
forms insoluble compounds with the alkalies, alkaline earths and other metallic 
oxides. It is soluble in alkaline carbonates, particularly the bicarbonates, and 
the solution deposites, after a time, lemon yellow crystals of a double car- 
bonate. The alkaline and earthy uranates assume, when ignited, a deep and 
very beautiful orange colour, which is most intense in the compounds with 
excess of base. This oxide is employed to colour glass of a delicate lemon- 
yellow tint. 

Sesqui-chloride of uranium, U 2 C1 3 , is very soluble in water, alcohol and 
ether. It forms a double salt of remarkable beauty with chloride of potassium, 
which crystallizes from a syrupy solution, 3KCH-U 2 Cl 3 -f 6HO. 

The uranic sulphate combines with sulphate of potash in three different pro- 
portions, forming the salts : 

2(K0,S0 3 )+U o 3 ,3S0 3 
3(KO,S03)4-U;o„3S03 + 3HO 
3KO, 4S0 3 +U 2 "0 3 , 3S0 3 +6HO. 
The proportion of the sulphuric acid and potash in the last salt is very extra- 
ordinary, but is the result of exact experiments, (Berzelius.) The formula, 
however, is not to be supposed to express the proximate constitution of the salt. 

The uranic nitrate is obtained by a slow evaporation in large tables, which 
like the other salts of this oxide are of a yellow colour. The nitrate is highly 
soluble both in water and alcohol. Uranic oxide is also said to form an acid 
salt with nitric acid, which is less soluble and more easily crystallized than the 
neutral salt. 

The mineral uranite is a double phosphate of lime and uranium, of which the 
formula is 3CaO, P0 5 -f-2(U 2 3 ,P0 5 ) + 24HO. 

* The atomic weight of uranium, indicated by the specific heat of the metal, is only 
677.8, or one-fourth of the number hitherto received, according to new researches of M. 
Regnault, (An. de Ch. et de Ph. t. 73, p. 71.) The oxide of uranium, at present considered 
as the protoxide, comes then to be U 4 0. M. Regnault has added greatly to the value of 
specific heat, as an element in fixing atomic weights, by confirming Dulong's general 
results by new experiments, and also by removing several of the exceptions to the law, 
that all simple atoms have the same capacity for heat, noticed at page 106. The elements 
enumerated below have the same capacity for heat, in the following atomic proportions, 
by Regnault's experiments : 

Bismuth . 1330 Cobalt . . 369 Antimony . 806.4 

Silver . . 675.5 Selenium . 494.6 Phosphorus . 196.1 

Uranium . 677.8 Arsenic . . 470 Carbon . . 152.9 



LANTANUM. 445 

CERIUM. 

Eq. 574.6 or 46.05; Ce. 

This metal was named Cerium by Hisinger and Berzelius, from Ceres. Al- 
though not an abundant element, it is found in a considerable number of mine- 
rals all from Sweden and Greenland. The mineral cerite is a eerous silicate, 
containing 68.6 per cent, of eerous oxide, with small quantities of lime and per- 
oxide of iron. This mineral is boiled in aqua regia, by which the silica is 
separated, and the other oxides dissolved. The iron is precipitated by benzoate 
of ammonia, and then ammonia added to the liquid, which throws down a mix- 
ture of eerous and eerie oxides. The oxides of cerium are reduced with diffi- 
culty, but by decomposing the eerous chloride by potassium, the metal was ob- 
tained by Mosander as a pulverulent mass of a dark chocolate brown, which 
gave a gray metallic trace under the burnisher. It oxidates quickly in water, 
disengaging hydrogen gas, particularly when the water is a little heated. 

Protoxide of cerium, Cerous oxide, CeO, is produced by calcining the 
mixed oxides of cerium, obtained as already described, by precipitating the 
solution of cerite in an acid by ammonia, till chlorine is no longer disengaged, 
as perceived by its odour. The salt that remains, when dissolved in water and 
precipitated by an alkali, gives the hydrate of cerous oxide, which soon becomes 
yellow in the air. The cerous salts are generally colourless, although some of 
them have an amethystine colour, like the salts of manganese. Their taste is 
sweet and afterwards astringent and they greatly resemble the salts of yttria. 
From these they may be distinguished by forming a salt with sulphate of potash 
of small solubility. They are precipitated white by the yellow prussiate of 
potash, not affected by sulphuretted hydrogen, and precipitated by an alkaline 
sulphuret with disengagement of sulphuretted hydrogen gas. 

Peroxide of cerium, Ceric oxide, Ce 2 3 , is obtained by calcining the cerous 
nitrate or carbonate. The ignited oxide is brick-red and pulverulent, easily 
soluble in acids, from which it is thrown down by an alkali as a mucilaginous 
matter, of a clear yellow colour, which is the hydrated oxide. This hydrate is 
not soluble in caustic alkalies, but alkaline carbonates dissolve a small quantity 
of it and become yellow. An intermediate compound, the ceroso-ceric oxide, 
is obtained when ceric oxide is exposed to hydrogen at a red heat. It is a 
lemon-yellow powder, which passes into ceric oxide by combustion in air. 
The salts of ceric oxide are distinguished from those of cerous oxide by their 
yellow and sometimes orange colour, by their taste which is sweetish-sour and 
strongly astringent. They are decomposed when boiled with hydrochloric 
acid, and converted into cerous salts with evolution of chlorine. 



LANTANUM. 

The oxide of this new metal was lately discovered by Mosander to exist in 
the cerite of Bastnas, forming indeed two-fifths of what is extracted from that 
mineral, by the ordinary process, as oxide of cerium. This throws considera- 
ble uncertainty over our knowledge of cerium, as the observations of chemists 
have not been made upon a pure substance. The new element alters but little 
the properties of cerium, and lies, therefore, as if concealed in it ; it was that 
fact which induced M. Mosander to apply the name lantanurn to the new metal. 
The oxide of lantanurn is not reduced by potassium, but this metal separates 
from the chloride of lantanurn a gray metallic powder, which undergoes oxida- 
38 



446 TANTALUM. 

tion in water, with disengagement of hydrogen gas, changing into a white 
hydrate. 

Oxide of lantanum. — It is prepared by calcining the nitrate of cerium as it 
is mixed with nitrate of lantanum. The oxide of cerium loses its solubility in 
very dilute acids, while the oxide of lantanum may be taken up by nitric acid 
diluted with 100 parts of water. The ignited oxide of lantanum has a brick- 
red colour, which does not appear to be due to oxide of cerium. It changes in 
hot water into a white hydrate which makes red litmus paper blue. This 
oxide is so powerful a base, that when digested in a solution of sal-ammoniac, 
it dissolves by degrees, expelling the ammonia. The atomic weight of lantanum 
is smaller than that assigned to cerium or rather to the mixture of the two 
metals, but has not been accurately determined. 

Sulphur et of lantanum is produced on heating the oxide strongly in the 
vapour of the sulphuret of carbon. It is pale yellow, decomposes water with 
disengagement of sulphuretted hydrogen, and becomes the hydrated oxide. 

The salts of lantanum have an astringent taste without any mixture of sweet- 
ness. Their crystals have generally a rose tint; sulphate of potash produces a 
precipitate in them, only when they are mixed with salts of cerium. 



DIDYMIUM. 

[Mosander has extended his investigations of the combinations of Lantanum 
and discovered a new metal — Didymium. This metal always accompanies 
yttrium, cerium and lantanum and is very difficult to separate from them. It is 
the cause of the brown colour of the ox. of cerium and the red of the oxide of 
lantanum. Its combinations have not yet been obtained sufficiently pure to de- 
termine its atomic weight. — Ann. der Chem. und. Pharm. No. 7, 1842. R. B.] 



TANTALUM. 

Syn. columbium. Eq. 2307.4 or 184.9; Ta. 

This metal appears to have been first observed in 1801, by Mr. Hatchett, in 
a black mineral belonging to the British Museum, and supposed to have come 
from Massachusetts in North America, and was named columbium on that 
account. M. Ekeberg found a new metal in 1802, which he called tantalum, 
in two Swedish minerals, then new, and named by him tantalite and yttrotan- 
talite. Their metal was fully studied by Berzelius ; and columbium, which had 
been imperfectly examined by Hatchett, was found by Dr. Wollaston, in 1809, 
to be the same metal. Tantalum has since been observed in two or three 
other minerals, but all of them among the rarest species. 

Tantalum is not reduced by carbon, but Berzelius obtained it by decom- 
posing the double fluoride of tantalum and potassium by potassium. It was a 
black powder, which could be washed and dried, and assumed an iron-gray 
metallic lustre under the burnisher. It took fire in air below a red heat and 
burned with much vivacity, yielding tantalic acid. No acid has a sensible 
action upon tantalum except hydrofluoric acid. Tantalum combines with 
oxygen in two proportions, forming tantalic oxide, Ta0 2 , and tantalic acid, 
Ta0 3 . 

Tantalic oxide, Ta0 2 , 2507.4 or 200.9. — This oxide is obtained on ex- 
posing tantalic acid in a charcoal crucible to the heat of a wind furnace, for an 
hour and a half. With the exception of the external film immediately in con- 
tact with the charcoal, which is metallic tantalum, the mass of acid is con- 



MERCURY. 447 

verted into tantalic oxide. This oxide is of a dark-gray colour, its particles 
are so hard as to scratch glass; it is soluble in no acid, not even in aqua regia 
or hydrofluoric mixed with nitric acid. The name tantalum was applied to 
the metal by Ekeberg, on account of this insolubility of its oxide in acids, in 
allusion to the fable of Tantalus. Heated to low redness in air, it burns 
slowly, and is converted, although not entirely, into tantalic acid. 

Tantalic acid, Ta0 3 , 2607.4 or 208.9.— It is in the state of tantalic acid 
that tantalum exists in most of its minerals, combined with the oxides of iron 
and manganese in tantalite, or with yttria in yttrotantalite. The acid may be 
obtained by fusing the mineral with carbonate of potash, and decomposing the 
tantalate of potash formed, by an acid, and also by fusion with bisulphate of 
potash (Berzelius, Traite, I, 392.) It presents itself as a white powder, which 
reddens litmus paper; when distilled in a retort, it parts with its water, which 
amounts to ll| per cent., Ta0 3 + 3HO, and loses the latter property. The 
density of the ignited acid is 6.5, in this state it is attacked by alkalies only. 
Tantalic acid dissolves by fusion in bisulphate of potash, and when hydrated in 
binoxalate of potash by the humid way. It is dissolved in small quantity by 
concentrated sulphuric acid, but precipitated from that solution by water. 

Sulphotantalic acia, TaS 3 , is prepared with most advantage by exposing 
tantalic acid to a bright red heat in a porcelain tube, and passing bisulphuret 
of carbon over it. It forms a gray pulverulent matter, having much the ap- 
pearance of plumbago. It is a good conductor of electricity. 

Chloride of tantalum, TaCl 3 , obtained on heating tantalum in pure chlorine 
gas, is, in the state of vapour, a yellow gas resembling chlorine, which con- 
denses into a white floury powder, having a shade of yellow, and in no way 
crystalline. 

Tantalic acid dissolves in alkalies and forms salts, but they are not crystal- 
lizable and are decomposed by all other acids even by carbonic acid. 



ORDER VIII. 

METALS OF WHICH THE OXIDES ARE REDUCED TO THE METALLIC 
STATE BY HEAT (NOBLE METALS.) 

SECTION I. 

MERCURY. 

Eq.1265.8 or 101.43; Hg (hydrargyrum.) 

Mercury or quicksilver, as it is named from its fluidity, has been known 
from all antiquity. The most valuable European mines of this metal are those 
of Idria in Illyria, and Almaden in Spain. It is fouud, to a small extent, in 
the metallic state. Its principal ore is a sulphuret, native cinnabar, from which 
the metal is obtained by distillation with lime or iron. The quicksilver of 
commerce is in general a highly pure substance. When contaminated with 
other metals, its fluidity is remarkably impaired. Mercury may be purified 
by distilling it from half its weight of iron turnings, or by digesting the metal 
with a small quantity of nitric acid, or with a solution of chloride of mercury > 
which rids it of the metals more oxidable than itself. 



448 MERCURY. 

Mercury is liquid at the usual temperature, its colour is white with a shade 
of blue when compared with silver, and it has a high metallic lustre. When 
pure, its surface does not tarnish in air. At 39 or 40 degrees below zero, 
mercury becomes solid; it crystallizes in regular octohedrons. According to 
M. Kupffer, the density of mercury at 39.2° is 13.5886; at 62.6°, 13.5569, 
and at 78.8°, 13.535. In the solid state, its density is about 14.0. At 662° 
it boils, forming a colourless vapour, of which the density was observed to be 
6976, by Dumas; the theoretical density is 6978. Mercury emits a sensible 
vapour between 68° and 80°, but not under 40°. When heated near its 
boiling point, mercury absorbs oxygen from the air, and forms crystalline 
scales of the red oxide. It is not affected by boiling hydrochloric or di- 
luted sulphuric acid, but is readily dissolved by diluted nitric acid. This 
metal never dissolves in hydrated acids, by substitution for hydrogen. Mer- 
cury combines with oxygen in two proportions, forming the black oxide, 
which is generally considered a suboxide, Hg 2 0, and the red oxide, composed 
of single equivalents, HgO, both of which are bases. The equivalent of mer- 
cury is then assumed to be 1265.8; but whether it should be this number or a 
multiple of it by two, we have no certain means of deciding, while in igno- 
rance of any isomorphous relation of mercury with the magnesian metals. 



MERCUROUS COMPOUNDS. 

Suboxide of mercury, (black oxide,) Mercurous oxide, Hg 2 0, 2631.6 or 
210.86. — This oxide is obtained by the action of a cold solution of potash, used 
in excess, upon calomel. They should be mixed briskly together in a mortar, 
in order that the decomposition be as rapid as possible, and the oxide be allowed 
to dry spontaneously in a dark place. Mr. Donovan finds these precautions 
necessary, from the disposition which this oxide possesses, to resolve itself into 
metallic mercury and the higher oxide. The decomposition of mercurous oxide 
is promoted by elevation of temperature, and by exposure to light. The mer- 
curous oxide is a black powder, of which the density is 10.69 (Herapath;) it 
unites with acids and forms a class of salts. It is precipitated as the black 
oxide by lime-water and the pure alkalies, and by alkaline carbonates as a 
white carbonate, which soon becomes black from decomposition. Its soluble 
salts are all partially decomposed by pure water, which combines with a portion 
of their acid, and throws down a subsalt containing an excess of oxide. They 
are precipitated black by sulphuretted hydrogen. The salts of the same oxide 
are decomposed by hydrochloric acid and soluble chlorides, with precipitation 
of calomel as a white powder, a property by which they are distinguished from 
the salts of the red oxide of mercury. 

The salts of this, and also of the red oxide, are reduced to the metallic state 
by copper and more oxidable metals, and by the proto compounds of tin. The 
precipitated mercury often presents itself as a gray powder, in which metallic 
globules are not perceived, and remains in this condition while humid. Mer- 
cury in this divided state possesses the medicinal qualities of the milder mercu- 
rials, and has often been mistaken for black oxide. To obtain precipitated 
mercury, equal weights of crystallized protochloride of tin (salt of tin) and cor- 
rosive sublimate may be dissolved, the first in diluted hydrochloric acid and the 
second in hot wafer, and the solutions mixed with stirring. The salt of tin 
assumes the whole chlorine of the corrosive sublimate, becoming bichloride of 
tin, which remains in solution, while the mercury is liberated, and forms so 
fine a precipitate, that it requires several hours to subside. It may be washed 
by affusion of hot water and subsidence, and slightly drained on a filter, but 
not allowed to dry. There can be no doubt that it is in this divided state, and 



MERCUROUS COMPOUNDS. 44^> 

not as the black oxide, that mercury is obtained by trituration with fat, turpen- 
tine, syrup, saliva, &c, in many pharmaceutical preparations. 

Subsu/phuret of mercury, Hg 2 S, is obtained by the action of sulphuretted 
hydrogen on a solution of the mercurous nitrate or upon calomel, as a black 
precipitate. This sulphuret is decomposed by a gentle heat, and resolved into 
globules of mercury and the higher sulphuret. 

Subchloride of mercury, Calomel, Hg 2 Cl, 2974.3 or 238.33.— -A variety of 
processes are given by pharmacians for the preparation of this remarkable sub- 
stance. It may be obtained in the humid way, by digesting U parts of mer- 
cury, with 1 part of pure nitric acid, of density from 1.2 to 1.25, till the metal 
ceases to be dissolved, and the liquid has begun to assume a yellow tint. A 
solution is also prepared of 1 part of chloride of sodium in 32 parts of distilled 
water, to which a certain quantity of hydrochloric acid is added, and this when 
heated to near the boiling point, is mixed with the mercurial salt. The mer- 
cury acquires the chlorine of the common salt, and the subchloride of mercury 
formed precipitates as a white powder, while the nitric acid and oxygen are 
resigned by the mercury to the sodium, which becomes nitrate of soda : NaCl 
and Hg 2 0,N0 5 =Hg 2 Cl and NaO,N0 5 . The excess of acid in this process is 
intended to prevent the precipitation of any subnitrate of mercury, which the 
dilution of the nitrate of mercury, on mixing the solutions, might occasion the 
formation of Calomel is also obtained by rubbing together, in a mortar, 4 
parts of chloride of mercury (corrosive sublimate) with three parts of running 
mercury. The mixture is afterwards introduced into a glass balloon, and 
sublimed by a heat gradually increased. Here the chloride of mercury com- 
bines with mercury, and the subchloride is produced. The same result is 
obtained by mixing the sulphate of red oxide of mercury, with as much mer- 
cury as it already contains, and about one-third of its weight of chloride of 
sodium, and subliming the mixture. The vapour of the subchloride of mercury, 
in these sublimations, is advantageously condensed by conducting it into a 
vessel containing hot water; the vapour of the water then condenses the salt in 
an extremely fine and beautifully white powder. The product of this operation 
is recommended by its purity, as well as its minute division, for chloride of 
mercury, by which the subchloride is accompanied, is dissolved by the water. 
It appears that whenever the subchloride is sublimed, a small portion of it is 
resolved into mercury and the chloride. To prepare the calomel for medical 
use, as it is usually condensed in a solid cake, it must, therefore, be reduced to 
a fine powder, and also be washed with hot water to remove the soluble chlo- 
ride. 

Subchloride of mercury is obtained by sublimation in four-sided prisms, 
terminated by summits of four faces. When the solid cake is finely pounded* 
the salt acquires a yellow tinge. The density of this salt 
in the solid condition is 6.5; in the state of vapour 8200, one Fig. 113. 
volume of which contains one volume of the vapour of mer- 
cury and half a volume of chlorine. This salt is so highly 
insoluble in water, that when the mercurous nitrate is added 
to hydrochloric acid diluted with 250,000 times its weight of 
water, a sensible precipitate of subchloride of mercury appears. 
When boiled for a long time in hydrochloric acid, this salt is 
resolved into chloride of mercury which dissolves, and mer- 
cury which is reduced.* 

Action of ammonia on subchloride of mercury. — The dry 
subchloride was found by Rose to absorb half an equivalent 

* [The same effect is produced by solutions of muriate of ammonia and alkaline chlo- 
rides. Mialhe, (Ann. de Chim. and de Phye. Dec. 1842,) states that the amount of calo- 

38* 




450 MERCURY. 

of ammonia, and to become black. Exposed to air the compound loses its 
ammonia, and the subchloride of mercury recovers its white colour. This 
ammoniacal compound is 2Hg 2 Cl-j-NH 3 . When calomel is digested in 
solution of ammonia, it becomes black, and was found by Dr. Kane to be con- 
verted into a double subamide and subchloride of mercury, a portion of sal- 
ammoniac being dissolved by the water at the same time, 

2Hg CI and 2NH 3 == Hg 2 Cl+Hg 2 NH 2 and NH 4 ,C1. 

This compound is not altered by boiling water ; when quite dry, it is of a 
gray colour. 

Subbromide of mercury, Hg 2 Br, is a white insoluble powder, resembling 
in all respects the subchloride, and formed in similar circumstances. A boil- 
ing solution of bromide of strontium was found by Lcewig to dissolve 3 
equivalents of calomel, of which 1 eq. precipitated, during the cooling of the 
solution. When the filtered solution was evaporated, it deposited a salt in 
small crystals, SrBr-f 2Hg 2 Br. These crystals were decomposed by pure 
water, and resolved into the insoluble subbromide Hg 2 Br, and a double salt 
which dissolved easily and crystallized by evaporation, SrBr-f Hg 2 Br. 

Subiodide of mercury, Hg 2 I, is obtained by precipitation as a green pow- 
der, which is red when heated. It is also formed by triturating mercury and 
iodine together in a mortar, with a few drops of alcohol, in the proportion of 
2 eq. of the former to 1 eq. of the latter. Another iodide of mercury was ob- 
tained by Boullay, by precipitating nitrate of suboxide of mercury with a 
solution of iodide of potassium, to which half an eqvivalent of iodine had been 
previously added. It is a yellow powder, which may be washed with alcohol ; 
from its composition it appears to be a compound of single equivalents of 
neutral iodide and subiodide of mercury, HgI4-Hg 2 I. 

No subcyanide of mercury exists, and it is doubtful whether a subfluoride y 
corresponding with the suboxide has been formed. 

Carbonate of black oxide of mercury, Hg0 2 ,C0 2 , precipitates as a white 
powder, when an alkaline carbonate is added to the nitrate of the same oxide. 
The precipitate becomes gray when the liquid containing it is boiled, and car- 
bonic acid escapes. This carbonate is soluble both in carbonic acid water, 
and in an excess of alkaline carbonate. 

Sulphate of black oxide of mercury, Mercurous sulphate, HgO,S0 3 ; 3132.8 
or 251.04. — It is obtained by digesting 1 part of mercury in l£ parts of sul- 
phuric acid, avoiding a high temperature, and interrupting the process as soon 
all the mercury is converted into a white salt. It is also precipitated when 
sulphuric acid is added to a solution of the nitrate of the same oxide. The salt 
may be washed with a little cold water. It crystallizes in prisms, and requires 
500 times its weight of cold and 300 of hot water to dissolve it. With water 
of ammonia this salt gives a dark-gray powder, containing ammonia or its- 
elements. 

Nitrates of black oxide of mercury, Mercurous nitrates. — The neutral 
nitrate is obtained, when mercury is dissolved in an excess of cold nitric acid, 
and crystallizes readily in transparent rhombs. It is soluble with heat in a small 
quantity of water, but is decomposed by a large quantity of water, and an inso- 
luble subsalt formed, unless nitric acid be added to the water. The formula of 
this salt is Hg 2 0,N0 5 -f 2HO. A subnitrate is formed when the black oxide 

mel altered by the action of muriate of ammonia differs with any variation in the relative 
proportion and the degree of concentration of the solution, a larger amount and greater 
concentration each increasing the effect. The presence of organic matters in the solution 
likewise influences the result, some as dextrine promoting, others as gum, lard, &c. re- 
tarding the charge. Even distilled water when boiled on calomel causes a slight modi6- 
cation in the union of its elements, a trace of corrosive sublimate being dissolved. R„ B.] 



MERCURIC COMPOUNDS. 451 

is dissolved in a solution of the preceding salt, or when an excess of mercury- 
is digested in diluted nitric acid at the usual temperature. It crystallizes readilv 
in white and opaque rhombic prisms, which contain, according to both G. 
Mitscherlich and Kane, 2N0 5 ,3Hg 2 and 3HO. This salt was observed by 
the former chemist to be dimorphous. When dissolved by dilute nitric acid, it 
gives the neutral salt. The subnitrate is soluble in a little water, but when 
treated with a large quantity, it leaves undissolved, like the neutral nitrate, a 
white powder, which as long as the supernatant liquid is acid retains its colour, 
but if it be washed with water becomes yellow. The yellow subnitrate of 
mercury was found to contain NO 5 ,2Hg 2 and HO (Kane.) When very dilute 
ammonia is added to the preceding soluble nitrates, without neutralizing the 
whole acid, a velvety black precipitate falls, known as Hahnemann's soluble 
mercury. This salt contains, according to the analysis of G. Mitscherlich, 
N0 5 ,3Hg 2 and NH 3 . But when pains were taken to avoid decomposition of 
the salt in washing it, its composition was found by Dr. Kane to be N0 5 ,2Hg 2 
and NH 3 . 

Acetate of black oxide of mercury, Hg o 0,C 4 H 3 3 , falls, when acetic acid or 
an acetate is added to the nitrate, in crystalline scales of a pearly lustre. It is 
anhydrous, and sparingly soluble in water. 



MERCURIC COMPOUNDS. 

Oxide of mercury (red oxide,) Mercuric oxide,HgO, 1365.8 or 109.43. — This 
compound is formed by the oxidation of mercury at a high temperature, as has 
already been described, or by heating the nitrate of mercury till all the nitric 
acid is expelled, and the mass, calcined almost to redness, no longer emits 
vapours of nitric oxide. As prepared by the last process, oxide of mercury 
forms a brilliant orange-red powder, crystallized in plates, and having the 
density 11.074. It is very dark-red at a high temperature, but becomes paler 
as it cools. When reduced to a fine powder it becomes yellow, like litharge, 
without any shade of red. It was found by Air. Donovan to be soluble to a 
small extent in water. If contaminated with nitric acid, it gives off nitrous 
fumes when heated in a glass tube, and a yellow sublimate of subnitrate also 
appears. This oxide is known in pharmacy as red precipitate. The same 
substance is obtained by precipitation, when a solution of corrosive sublimate 
is mixed with an excess of caustic potash, as a dense powder of a lemon-yellow 
colour. It is necessary to use the potash in excess, otherwise a dark-brown 
oxichloride is formed. The precipitated oxide parts with a little moisture, when 
gently heated, but does not change in appearance. At a red heat, the oxide of 
mercury is entirely volatilized in the form of oxygen and metallic mercury. 

When water of ammonia is digested for several days upon precipitated oxide 
of mercury, the latter is converted into a yellowish-white powder, which Dr. 
Kane considers as Hg,NH 2 -f 2HgO + 3H0, or a hydrated compound of amide 
and oxide of mercury. 

Sulphur et of mercury, Cinnabar, HgS, 1467 or 1 17.55. — This is the common 
ore of mercury, and sometimes occurs crystallized forming a beautiful vermilion. 
It is prepared artificially, by fusing one part of sulphur in a crucible, and adding 
to it by degrees six or seven parts of mercury, stirring it after each addition, 
and covering it to preserve it from contact of air, when it inflames from the heat 
evolved in the combination. The product is exposed to a sand bath heat, to 
expel the sulphur uncombined with mercury, and afterwards sublimed in a glass 
matrass by a red heat. A brilliant red mass of a crystalline structure is thus 
obtained, which when reduced to fine powder forms the lively red pigment, 
vermilion. This sulphuret is black before sublimation. It is precipitated black 



452 MERCURY. 

also when sulphuretted hydrogen is sent through a solution of corrosive subli- 
mate ; but is of the same composition in both states. The sulphuret of mercury, 
however, may be obtained of a red colour without sublimation, or in the humid 
way, by several methods. 

Liebig recommends for this purpose to moisten the preparation called white 
precipitate, recently prepared, with the sulphuret of ammonium, and allow them 
to digest together. The black sulphuret is instantly produced, which in a few 
minutes passes into a fine red cinnabar, the colour of which is improved by 
digesting it at a gentle heat in a strong solution of hydrate of potash. The 
sulphuret of ammonium used in this experiment is prepared by dissolving sul- 
phur in hydrosulphuret of ammonia to saturation. Cinnabar is not attacked by 
sulphuric, nitric or hydrochloric acid, nor by solutions of the alkalies, but it is 
dissolved by aqua regia. 

Chloride of mercury, Corrosive sublimate, 1708.5 or 136.9. — This salt may 
be formed by dissolving red oxide of mercury in hydrochloric acid, or by adding 
hydrochloric acid to any soluble salt of that oxide, but it is generally prepared 
in a different manner. Four parts of mercury are added to five parts of sul- 
phuric acid, and the mixture boiled till it is converted into a dry saline mass. 
The mercuric sulphate thus obtained is mixed with an equal weight of common 
salt, and heated strongly in a retort by a sand bath; chloride of mercury sub- 
limes and condenses in the upper part and neck of the retort, while sulphate of 
soda remains behind with the excess of chloride of sodium. The mercury and 
sodium have exchanged places in the salts : 

NaCl and HgO,S0 3 =HgCl and NaO,S0 3 . 

Mercury, when heated in a stream of chlorine gas, burns with a pale flame, 
and is converted into a white sublimate of chloride. The salt has been pre- 
pared on a large scale in this manner, which was suggested as a manufacturing 
process by Dr. A. T. Thompson. 

The sublimed chloride of mercury forms a crystalline mass, of which the 
density is 6.5 ; it fuses at 509°, and boils about 563°. The vapour of chloride 
of mercury is colourless, its density 9420, 1 volume of it containing 1 volume 
of mercury vapour and 1 volume of chlorine gas. This salt is soluble in 16 
parts of cold and in 3 parts of boiling water, in 2£ parts of cold and in l\ part 
of boiling alcohol, and in 3 parts of cold ether. It is not decomposed by sul- 
phuric or nitric acid ; is largely dissolved by the latter and also by hydrochloric 
acid. It is obtained by sublimation and from solution, in two different crystal- 
line forms. The solutions of chloride of mercury exposed to the direct rays of 
the sun evolve oxygen, while hydrochloric acid is dissolved and subchloride of 
mercury precipitates. The decomposition of this salt, by the action of light, is 
greatly more rapid when the solution contains organic matter. The poisonous 
action of chloride of mercury, which is scarcely inferior to that of arsenious 
acid, is best counteracted by liquid albumen, with which chloride of mercury 
forms an insoluble and inert compound. 

The solution of chloride of mercury affords a yellow or brown precipitate 
with the hydrates of potash and soda, and with lime-water ; a black precipitate 
with sulphuretted hydrogen, and a fine scarlet precipitate with iodide of potas- 
sium. Mercury is thrown down from that solution by metallic copper. A drop 
of the solution does not tarnish polished gold, but if the moistened surface be 
touched by zinc or iron, mercury is immediately precipitated, and produces a 
blue stain upon the surface of the gold, while the common metal dissolves. 

Chloride of mercury and ammonia. — When chloride of mercury is gently 
heated in a stream of ammoniacal gas, the latter is absorbed, and the compound 
fuses from heat evolved in the combination. The product was found by Rose 
to contain half an equivalent of chlorine, 2HgCl-fNH 3 . This compound boils 



WHITE PRECIPITATE. 453 

at 590° and may be distilled without loss of ammonia ; it is decomposed by 
water. When the double chloride of mercury and ammonium, called sal-alem- 
broth, is precipitated by potash in the cold, a white powder is obtained, which 
was first distinguished by Wohler from the compound next described; its 
composition may be expressed, from the analysis of Dr. Kane, by HgC+lNH 3 . 
The same compound is also formed when ammonia is added to a solution of sal- 
ammoniac, and chloride of mercury dropped into the liquid, brought to the boiling 
point, so long as the precipitate which is produced is redissolved. The com- 
pound appears on the cooling of the solution, in small crystals, which are garnet 
dodekahedrons (Mitscherlich). The crystalline form of this compound, there- 
fore, belongs to the regular system, like that of sal-ammoniac. 

The compound known as white precipitate, is formed when ammonia is 
added to a solution of chloride of mercury. When first produced, it is bulky 
and milk white; it is decomposed by hot water or by much washing with cold 
water, and acquires a yellow tinge. Dr. Kane has demonstrated that white 
precipitate is free from oxygen, and contains nothing but the elements of a 
double chloride and amide of mercury, and represents it by the formula, 
HgCl-{-Hg,NH 2 . White precipitate is distinguished from calomel by solu- 
tion of ammonia, which does not alter the former, but blackens the latter; it 
is readily dissolved by acids. Mitscherlich has observed that when white 
precipitate is gradually heated by a metal bath, and the heat continued for a 
long time, three atoms of it lose two atoms of ammonia and one atom of chlo- 
ride of mercury, while a red matter remains in crystalline scales, having much 
the appearance of red oxide of mercury produced by the oxidation of the metal 
in air, which contains two atoms of chloride of mercury united with a com- 
pound of one atom of nitrogen and three atoms of mercury, 2HgCl-f NHg 3 . 
He concludes, that the atom of white precipitate should be multiplied by three, 
its decomposition by the heat of the metal bath would then be represented 
thus: 

3HgCl+3(Hg,NH 2 )==2HgCl+NHg 3 and 2NH 3 and HgCl. 

The red compound is itself decomposed by a temperature above 680°, and 
resolved into chloride of mercury, mercury and nitrogen. It is insoluble in 
water, and is not altered in boiling solutions of the alkalies. It may be boiled 
without change in diluted or concentrated nitric acid, and in pretty concen- 
trated sulphuric acid, but it is decomposed and dissolved when boiled in the 
most concentrated sulphuric acid or in hydrochloric acid; no gas is evolved, but 
chloride of mercury and ammonia are found in the acid solution. The com- 
pound NHg 3 is not isolated, by passing ammonia over the heated red com- 
pound. Mercury conducts itself in these compounds in the same way as po- 
tassium with ammonia; the olive-coloured substance produced by the action 
of dry ammonia upon potassium being the amide of potassium, 3(K,NH 2 ,) 
and the plumbago-looking substance left on heating the amide of potassium, 
when ammonia escapes, a compound of nitrogen and potassium, NK 3 .* 

When white precipitate is boiled in water, it is changed into a heavy cana- 
ry yellow powder, which Dr. Kane has shown to be a compound of the double 
chloride and amide of mercury with oxide of mercury, HgCl -f Hg,NH 2 -f2HgO. 
Two atoms of water are decomposed in its formation, the two atoms of oxy- 
gen which are found in the yellow compound, while the two atoms of hydro- 
gen, added to an atom of chlorine and an atom of amidogen, form an atom of 
hydrochlorate of ammonia which is found in solution: 

2(HgCl+HgNH 2 )&2HO=HgCl+Hg,NH 2 +2HgO&NH 4 ,Cl. 

* Mitscherlich in Poggendorff 's Annalen, vol. 39, p. 409. 



454 MERCURY. 

Solutions of potash and soda convert white precipitate into the same yellow 
substance, while a metallic chloride is formed and ammonia evolved (Kane.) 

Oxichloride of mercury. — When a solution of corrosive sublimate is preci- 
pitated by potash or soda, mercuric oxide goes down in combination with a 
portion of chloride, as a brown precipitate, unless a considerable excess of 
alkali be employed. The same oxichloride is produced by an alkaline carbo- 
nate, but a double carbonate is then also formed. Chloride of mercury is not 
immediately precipitated by the bicarbonates of potash and soda, and, hence, 
that salt may be employed to detect the presence of a neutral alkaline carbo- 
nate in these bicarbonates. This oxichloride may also be formed by passing 
chlorine through a mixture of water and oxide of mercury. It may be ob- 
tained crystalline and of a very dark colour, almost black, by mixing corrosive 
sublimate with chloride of lime, and boiling the liquid, or by treating a solu- 
tion of corrosive sublimate with bicarbonate of potash, and allowing the solu- 
tion to stand in an open vessel, when carbonic acid gradually escapes, and 
the compound HgCl-f 4HgO is deposited. This oxichloride is decomposed 
by a moderate heat, chloride of mercury sublimes and the red oxide is left. 

Chloride and sulphuret of mercury, HgCl4-2HgS. — When sulphuretted 
hydrogen gas is passed through a solution of chloride of mercury, the preci- 
pitate which first appears, and does not subside readily, is white; it has been 
shown by Rose to be a compound of chloride and sulphuret of mercury. This 
substance is changed entirely into sulphuret of mercury, when left in water 
containing sulphuretted hydrogen. On the other hand, precipitated sulphuret of 
mercury digested in a solution of chloride of mercury, takes down that salt 
and forms the compound in question. Sulphuret of mercury combines likewise 
with the bromide, iodide, fluoride and nitrate of mercury, and always in the 
proportion of two atoms of the sulphuret to one atom of the other salt. 

Double salts of chloride of mercury. — Chloride of mercury was found by 
M. BonsdorfF to combine with chloride of potassium in three different pro- 
portions, forming a series of salts in which the chloride of potassium remains 
as one equivalent, while the chloride of mercury goes on increasing. They 
are, KCl-f HgCl+HO, which crystallizes in large transparent rhomboidal 
prisms; KCl-|-2HgCl-f 2HO crystallizing in fine needle-like amianthus; and 
KC14- 4HgCl + 4HO, which crystallizes also in fine needles. Chloride of 
sodium forms only one compound, NaCl + 2HgCl-f4HO which crystallizes 
in fine regular hexahedral prisms. One of the double salts of chloride of am- 
monium has long been known as sal-alembroth. It crystallizes in flattened 
rhomboidal prisms, NH 4 Cl+HgCl-f HO, and is isomorphous with the cor- 
responding potash salt. It loses the water it contains in dry air, without 
change of form. Dr. Kane has also obtained NH 4 Cl-f-2HgCl, and the same 
with an atom of water, NH 4 Cl-f-2HgCl-f HO, the first in a rhomboidal form, 
and the second in long silky needles. All these double chlorides are obtained 
by dissolving their constituent salts together in the proper proportions. 
Chlorides of barium and strontium form compounds in good crystals with 
chloride of mercury, BaCl + 2HgCl + 4HO, and SrCl-f 2HgCl + 2HO. 
Chloride of calcium combines in two proportions with the mercurial chloride. 
When chloride of mercury is dissolved to saturation in chloride of calcium, 
tetrahedral crystals separate from the solution, which are pretty persistent in 
air, CaCl-f 5HgCl-f8HO. After the deposition of these crystals, the liquid 
affords, when evaporated by a gentle heat, a second crop of large prismatic 
crystals, CaCl-f 2HgCl-f 6HO, which are very deliquescent. Chloride of 
magnesium also forms two salts, MgCl-f- 3HgCl 4- HO, and MgCl + HgCi 
-f- 6HO, both deliquescent. Chloride of nickel gives two compounds, of 
which, one crystallizes in tetrahedrons, like the chloride of calcium salt. 
Chloride of manganese forms a compound in good crystals; MnCl-f HgCl-f 



CYANIDE OF MERCURY. 455 

4HO. Chloride of iron and zinc form similar isomorphous salts, FeCl-f Hg 
CI + HO, and ZnCl-f-HgCl-f HO. The double chlorides of zinc and of 
manganese are remarkable in one respect, that chloride of mercury dissolved 
by them in excess, crystallizes by evaporation in fine large crystals, such as 
cannot be obtained in any other way. Chlorides of cobalt, nickel, and copper 
form similar crystallizable salts; but chloride of lead, on the contrary, does 
not appear to form a double salt with chloride of mercury (BonsdorfT.) 

Bromide of mercury, HgBr, 2244. 1 or 179.82. — This salt is obtained by 
treating mercury with water and bromine. It is colourless, soluble in water 
and alcohol, and when heated, fuses and sublimes, exhibiting a great analogy 
to chloride of mercury in its properties. Its density in the state of vapour is 
12,370. Bromide of mercury forms a similar compound with sulphuret of 
mercury HgBr-f 2HgS, which is yellowish. It was also combined, by 
BonsdorfT, with a variety of alkaline and earthy bromides. Bromide of 
mercury combines with half an equivalent of ammonia, in the dry way, and 
also gives a white precipitate, with solution of ammonia, analogous to that 
derived from chloride of mercury. 

Iodide of mercury, Hgl, 2845.3 or 228. — It falls as a precipitate of a tine 
scarlet colour, when iodide of potassium is added to a solution of chloride of 
mercury. It may also be obtained by triturating its constituents together, in 
the proper proportion, with a few drops of alcohol. To procure it in crystals, 
M. Mitscherlich dissolves iodide of mercury to saturation, in a hot concen- 
trated solution of the iodide of potassium and mercury, and allows the solu- 
tion to cool gradually. When heated moderately, iodide of mercury becomes 
yellow; at a higher temperature it fuses and sublimes, condensing in rhom- 
boidal plates of a fine yellow colour. The forms of the red and yellow crys- 
tals are totally different, so that the change of colour is due to the dimorphism 
of iodide of mercury. The yellow crystals generally return gradually into 
the red state, when cold, and this change may be determined at once by 
scratching the surface of a crystal, or by crushing it. The density of iodide 
of mercury in the state of vapour, is 15,680; it is the heaviest of gaseous 
bodies. Iodide of mercury is slightly soluble in water, but requires more than 
6000 times its weight of water to dissolve it. It is much more soluble in alco- 
hol and in acids, particularly with the assistance of heat. Iodide of mercury 
is very soluble in iodide of potassium; it is also dissolved by a hot solution of 
chloride of mercury. 

When treated with sulphuretted hydrogen water, iodide of mercury forms 
the compound HgI-f2HgS, which is yellow. Iodide of mercury absorbs a 
whole equivalent of dry ammoniacal gas, Hgl-f NH 3 . The compound 
is white, but loses ammonia in the air and becomes red. Iodide of 
mercury unites with other iodides, and forms a class of salts as extensive 
as the compounds of chloride of mercury. They have been studied by M. 
P. Boullay.* Iodide of mercury also combines with chlorides; it is dis- 
solved by a hot solution of chloride of mercury, and two compounds have 
been obtained on the cooling of the solution, a yellow powder, Hgl-f-HgCl, 
and white dendritic crystals, HgI-f-2HgCl. 

Cyanide of mercury, HgCy, 1595.7 or 127.87. — This salt is most easily 
obtained by saturating hydrocyanic acid with red oxide of mercury. To pre- 
pare the hydrocyanic acid required, the process of Winkler may be followed. 
Fifteen parts of ferrocyanide of potassium are distilled with 13 parts of oil 
of vitriol diluted with 100 parts of water, and the distillation continued by a 
moderate heat nearly to dryness. The vapour should be made to pass through 
a Liebig's condensing tube, and be afterwards received in a flask containing 



* An. de Chim. et de Phys., t. 34, p. 337. 



M 



456 MERCURY. 

30 parts of water. A portion of the condensed hydrocyanic acid is put aside, 
and the remainder mixed with 16 parts of oxide of mercury in fine powder, 
and well agitated till the odour of hydrocyanic acid is no longer perceptible. 
The solution is drawn off from the undissolved oxide of mercury, and the re- 
served portion of hydrocyanic acid mixed with it. The last addition is 
necessary to saturate a portion of oxide of mercury, which cyanide of mer- 
cury dissolves in excess. This operation yields 12 parts of 
Fig. 114. the salt in question. Cyanide of mercury crystallizes in 
square prisms, which are anhydrous, and resembles chloride 
of mercury in its solubility and poisonous qualities. The 
red oxide of mercury, even when dry, absorbs hydrocyanic 
acid, with the formation of water and evolution of heat. The 
affinity of mercury for cyanogen appears to be particularly 
intense; oxide of mercury decomposing all the cyanides, even 
cyanide of potassium and liberating potash. Cyanide of 
^ mercury is consequently not precipitated by potash. Nor is 
^^^— t^>' it decomposed by any acid, with the exception of hydrochlo- 
ric, hydriodic and sulphuretted hydrogen. By a heat ap- 
proaching to redness, cyanide of mercury" is decomposed, and resolved into 
mercury and cyanogen gas. When hydrocyanic acid is digested upon mer- 
curous oxide, the mercuric cyanide dissolves, and metallic mercury is libe- 
rated. 

Oxicyanide of mercury, HgCy-J-HgO, appears when hydrocyanic acid of 
considerable strength (10 or 20 per cent.) is agitated with red oxide of mer- 
cury in large excess, as a white powder intermixed with red oxide. It is 
sparingly soluble in cold water, but may be dissolved out by hot water, and 
crystallizes on cooling in transparent four-sided acicular prisms. When 
heated gently, it blackens slightly, and then explodes. (Mr. Johnston, Phil. 
Trans. 1839, p. 113.) 

Cyanide of mercury, when digested upon red oxide of mercury, dissolves 
a large quantity of it, and forms, according to M. Kuhn, a tribasic cyanide of 
mercury, HgCy-f-3HgO, which is more soluble in water than the neutral 
cyanide, and crystallizes with more difficulty in small acicular crystals. 

Cyanide of mercury and potassium, KCy+HgCy, is formed 3 on dis- 
solving cyanide of mercury in a solution of cyanide of potassium, and crys- 
tallizes in regular octohedrons. Cyanide of mercury forms also crystallizable 
double salts with other cyanides, such as the cyanides of sodium, barium^ 
calcium, magnesium, &c. It also combines with chlorides, bromides, iodides, 
and also with several oxi-salts, such as chromate and formiate of potash, 2(KO, 
Cr0 3 ) + HgCy and KO,F + HgCy. 

Sulphate of mercury, Mercuric sulphate, HgO,S0 3 ; 1867 or 149.6. — It is 
formed by boifing 5 parts of sulphuric acid upon four parts of mercury, till the 
metal is converted into a dry saline mass. Sulphate of mercury is a white 
crystalline salt, neutral in composition, but which, like most of the neutral salts 
of mercury, cannot exist in solution. It gives a dense yellow powder when 
decomposed by water, and sulphuric acid is dissolved. This subsulphate is 
known as turbith mineral, a name applied to it by the old chemists, because it 
was supposed to produce effects in medicine analogous to those of a root for- 
merly employed, and known as convolvulus turpethum. The composition of 
turbith mineral is HgO,S0 3 +2HgO (Kane.) Solution of ammonia converts 
both the neutral sulphate and turbith mineral into a heavy powder, which Dr. 
Kane names ammonio-turbith, and finds to be HgO,S0 3 -f-Hg,NH 2 -f 2HgO. 
It is, therefore, analogous in composition to the yellow powder produced by the 
decomposition of white precipitate. 
Nitrates of the red oxide of mercury, Mercuric nitrates. — The neutral 



MERCURIC NITRATES. 457 

nitrate cannot be crystallized, but it exists in solution, when chloride of mer- 
cury is precipitated by nitrate of silver. When red oxide of mercury is 
dissolved in nitric acid, or when the metal is dissolved in the same acid with 
ebullition, till a drop of the solution no longer occasions a precipitate in water 
containing a soluble chloride, a subnitrate is formed crystallizing in small prisms, 
which are deliquescent in damp air. Its composition is expressed by HgO, 
N0 5 -f-HgO-j-2HO. It is the only crystallizable nitrate of this oxide. Decom- 
posed by water, this salt yields yellow subnitrate, which when washed in its 
preparation by warm, but not boiling water, is HO,N0 5 -f 3HgO. When the 
subnitrate is prepared by boiling water, it has a red colour, and probably con- 
sists of N0 5 -f 6HgO (Kane.) 

Nitrate of mercury affords several compounds when treated with ammonia. 
When a dilute, and not very acid solution of that salt is treated in the cold, by 
weak water of ammonia not added in excess, a pure milk-white precipitate 
appears, which is not granular, and remains suspended in the liquid for a con- 
siderable time. It was analyzed by G. Mitscherlich, and to distinguish it from 
some other salts containing the same constituents, I shall name it Mitscher* 
lich's ammonia subnitrate. It contains N0 5 ,3HgO and NH 3 , which Dr. Kane 
would arrange thus, NH 3 >N0 5 -f 3HgO, making the ammonia or amide of 
hydrogen basic to the acid. The preceding compound is altered in its appear- 
ance by boiling water, and becomes much heavier and more granular, forming 
Soubeiran's ammonia subnitrate, the composition of which Dr. Kane finds to 
be HgO,N0 5 -fHg,NH 2 -f2HgO; or it resembles in constitution the bodies 
already described containing chlorine and sulphuric acid. The yellow crys- 
talline ammonia subnitrate, a third compound, was obtained by G. Mitscher- 
lich by boiling the ammonia subnitrate with an excess of ammonia, and adding 
nitrate of ammonia by which a portion of the powder is dissolved; the solution, 
as it cools and loses ammonia, yields small crystalline plates of a pale yellow 
colour. The constituents of this salt are N0 5 ,2HgO and NH 3 . Dr. Kane 
doubles its equivalent and represents it as a compound of Soubeiran's salt with 
nitrate of ammonia, as it appears to be produced by the solution of the former 
salt in the latter,i(HgO,N0 5 -f Hg,NH 2 +2HSO)-f NH 4 0,N0 5 . Soubeiran's 
ammonia subnitrate is dissolved in considerable quantity, when boiled in a 
strong solution of nitrate of ammonia and the solution deposites, on cooling, 
small but very brilliant needles, which were observed and analyzed by Dr. 
Kane. Kane's ammonia subnitrate is decomposed by water, nitrate of am- 
monia dissolving and Soubeiran's subsalt being left undissolved. It contains 
the elements of 3(NH 4 0,N0 5 ) and 4HgO. Dr. Kane believes that it is most 
likely to contain Soubeiran's subnitrate ready formed, which leaves 2 atoms of 
nitrate of ammonia and 2 atoms of water to be otherwise disposed of.* 

Nitrate of mercury forms an insoluble compound with sulphuret of mercury, 
HgO,N0 5 -f 2HgS, resembling the compounds of the sulphate and chloride with 
sulphuret of mercury. It also forms double salts with iodide and cyanide of 
mercury. 

* Trans, of the Royal Irish Academy, voK six. pt. 1 ; or, Am de Ch. et de Ph. t. 72, 
p. 225. 



39 



458 SILVER. 



SECTION II. 



SILVER. 
Eq. 1351. 6 or 108.3; Ag (argcntum.) 

This metal is found in various parts of the world, and occurring often in the 
metallic state and being easily melted must have attracted the attention of man- 
kind at an early period. Before the discovery of America, the silver mines of 
Saxony were of considerable importance, but the silver mines of Mexico and 
Peru far exceed in value the whole of the European and Asiatic mines; the 
former have furnished during the last three centuries, according to Humboldt, 
316 millions of pounds troy of pure silver. 

A considerable quantity of silver is obtained from ores of lead by cupellation, 
as has already been described under that metal. The native silver, which is 
in the condition of threads or thin leaves, is separated from the gangue or 
accompanying rock, by amalgamation, a process which is also followed in the 
treatment of the most frequent ore of silver, the sulphuret, when it is not accom- 
panied by sulphuret of lead. The last ore, ground to powder, is roasted in a 
reverberatory furnace with 10 per cent, of chloride of sodium, by which the 
silver is converted into chloride. It is then introduced into barrels, with water, 
iron and a quantity of metallic mercury, and the materials kept in a state of 
agitation for eighteen hours by the revolution of the barrels on their axes. The 
chloride of silver, although insoluble, is reduced to the metallic state by the iron, 
and chloride of iron is produced, while the silver forms a fluid compound with 
the mercury. By adding more water and turning the barrels more slowly, the 
fluid amalgam separates and subsides. It is drawn off and subjected to pres- 
sure in a chamois leather bag; the mercury passes through the leather, while 
a soft amalgam of silver remains in the bag. The mercury is afterwards 
separated from this amalgam, by a species of distillation, per descensum, and 
the silver remains. Where machinery cannot be applied and iron is not used, 
the waste of mercury in the amalgamation is considerable. Mr. P. Johnston 
proposes to diminish the loss of mercury, as soluble chloride, which then occurs, 
by using an amalgam of zinc and mercury, instead of pure mercury. 

Silver is obtained free from other metals and in a state of purity, for chemical 
and other purposes, in two different ways. 1. The metal is dissolved in pure 
nitric acid, slightly diluted, and precipitated by a solution of chloride of sodium; 
the salts of the other metals present remain in solution. The insoluble chloride 
of silver, thus obtained, is washed well upon a filter with hot water and dried. 
A quantity of carbonate of potash, equal to twice the weight of the silver, is 
fused in a crucible, and the chloride of silver gradually added to it ; chloride of 
potassium is formed, and carbonic acid and oxygen escape with effervescence. 
The crucible is then exposed to a sufficient heat to fuse the reduced silver, which 
subsides to the bottom. 2. The mode of separating silver from the common 
metals, in the ordinary practice of assaying, is like many metallurgic operations, 
an exceedingly elegant and refined process. A portion of the silver alloy, the 
assay, is fused with several times its weight of pure lead (an alloy of 1 copper 
and 15 silver with 96 lead for instance) upon a bone-earth cupel, which is sup- 
ported in a little oven or muffle, heated by a proper furnace. Air being allowed 
access to the assay, the lead is rapidly oxidated, and its highly fusible oxide 
imbibed, as it is produced, by the porous cupel. The disposition of copper and 
other common metals to oxidate is increased by the presence of the lead, and 



SUBOXIDE OF SILVER. 459 

their oxides, which form fusible compounds with oxide of lead, are removed in 
company with the latter. When the foreign metal is nearly entirely removed, 
the assay is observed to become rounder and more brilliant, and the last trace 
of fused oxide occasions a beautiful play of prismatic colours upon its surface, 
after which, the assay becomes, in an instant, much whiter, ox flashes, an indi- 
cation that the cupellation is completed. 

Pure silver is the whitest of the metals, and susceptible of the highest polish; 
when granulated by being poured from a height of a few feet into water, its 
surface is rough, but its aspect peculiarly beautiful. It crystallizes in the cube 
and regular octohedron, both from a state of fusion and by precipitation from 
solution. Silver is in the highest degree ductile and malleable ; its density varies 
between 10.474 and 10.542, it fuses at 1873°. When in the liquid state, it is 
capable of absorbing oxygen gas from the air, which is discharged again in the 
solidification of the metal, and gives rise to a sort of vegetation upon its surface, 
or even occasions the projection of small portions of the silver to a distance, an 
accident which is known in assaying as the spilling of the metal. Gay-Lussac 
observed that when a little nitre was thrown upon the surface of melted silver 
in a crucible, and the whole kept in a state of fusion for half an hour, a very 
considerable absorption of oxygen took place. When the crucible w r as removed 
from the fire and quickly placed under a bell-jar filled with water, which can 
be done without danger, the silver discharged a quantity of oxygen equal to 20 
times its volume. This property is possessed only by pure silver, it does not 
appear at all in silver containing 1 or 2 per cent, of copper. As oxide of silver 
is reduced by a red heat, the absorption of the oxygen by the fluid metal must 
be a phenomenon of a different nature from simple oxidation. 

Silver does not combine with the oxygen of the air at the usual temperature, 
nor even when heated ; the tarnishing of polished silver in air is occasioned by 
the formation of sulphuret of silver. Silver does not dissolve in any hydrated 
acid, by substitution for hydrogen, but on the contrary, it is displaced from a 
solution in an acid, by hydrogen and precipitated in the metallic state. This 
metal is also precipitated by mercury and all the more oxidable metals. Its 
salts are reduced at the usual temperature by sulphate of iron, of which the 
protoxide is converted into peroxide. But if the persulphate of iron be boiled 
upon the precipitated silver, the latter is dissolved again, and oxide of silver and 
protoxide of iron reproduced. Silver, however, is oxidated when fused or 
heated strongly in contact with substances for which oxide of silver has a great 
affinity, as with a siliceous glass, and stains the glass yellow. It is oxidated by 
boiling concentrated sulphuric acid, with the escape of sulphurous acid. Silver is 
readily dissolved by nitric acid, with a gentle heat, and with much violence, at 
a high temperature, nitrate of silver is formed and nitric oxide escapes. Silver 
combines in three proportions with oxygen forming a suboxide, Ag 3 0, protoxide 
AgO and peroxide Ag0 2 . 

Suboxide of silver, Ag 2 0. — The existence of this oxide has only very 
recently been established beyond doubt by M. Wohler. The pure protoxide 
of silver is completely reduced to the state of metal by hydrogen gas, at 212° ; 
but the oxide contained in citrate of silver loses only half its oxygen in the same 
circumstances, the suboxide being formed and remaining in combination with 
one-half of the citric acid of the former salt. The solution in water of the sub- 
oxide salt is dark-brown, and the suboxide is precipitated black from it by 
potash. When the solution of the subsalt is heated, it becomes colourless, and 
metallic silver appears in it. The salt dissolves of a brown colour in ammonia. 
Several other salts of silver, containing organic acid, comport themselves in the 
same way as the citrate, when heated in hydrogen.* 

* Liebig's Annalen, vol, 30, p. 1, 1839. 



460 SILVER. 

Protoxide of silver, AgO, 1451.6 or 116.3. — It is thrown down when potash 
or lime-water is added to a solution of nitrate of silver, as a brown powder, 
which becomes of a darker colour when dried. The powder was found to be 
anhydrous by Gay-Lussac and Thenard; its density is 7.143, according to 
Herapath. Oxide of silver is a powerful base, and forms salts, several of which 
have been found isomorphous with the corresponding salts of soda. It is solu- 
ble, like oxide of lead, to a small extent in pure water, free from saline matter, 
and the solution has an alkaline reaction. Oxide of silver is not dissolved by 
solutions of the hydrates of potash and soda. Its salts are precipitated black 
by sulphuretted hydrogen, and afford, when treated with hydrochloric acid or 
a soluble chloride, a white curdy precipitate, the chloride of silver, which soon 
becomes purple, if exposed, while humid, to the direct rays of the sun. This 
precipitate is not dissolved by nitric acid, but is dissolved by ammonia in com- 
mon with most of the insoluble salts of silver. 

Oxide of silver combines with ammonia and forms the fulminating ammoni- 
aret of silver, a substance of a dangerous character from the violence with * 
which it explodes. The ammoniaret may be formed by digesting newly pre- 
cipitated oxide of silver in strong ammonia, or more readily by dissolving nitrate 
of silver in ammonia, and precipitating the liquor by potash in slight excess. If 
this substance be pressed by a hard body, w T hile still humid, it explodes with - 
unequalled violence ; when dry, the touch of a feather is often sufficient to cause 
it to fulminate. The explosion is obviously occasioned by the reduction of the 
silver, from the combination of its oxygen with the hydrogen of the ammonia, 
and the evolution of nitrogen gas. 

Sulphur et of silver, AgS, 1552.8 or 124.43. — Sulphur and silver maybe 
combined together by fusion ; the excess of sulphur escapes, and at a high tem- 
perature the sulphuret melts ; it forms, on cooling, a crystalline mass. This 
compound has a lead-gray colour and metallic lustre. It is so soft that it may 
be cut by a knife, and is malleable. The sulphuret of silver is also remarkable 
for conducting electricity, like a metal, when warmed. The same compound 
occurs in nature, sometimes crystallized in octohedrons with their secondary 
faces. This sulphuret is particularly interesting from being isomorphous with 
the subsulphuret of copper, AgS with Cu 2 S (page 120.) These two sulphurets 
replace each other in indeterminate proportions in several double sulphurets of 
silver and other metals, as in polybasile and fahlerze, the composition of which 
may be expressed by the following formulas, the symbols placed above each 
other, representing constituents, of which either the one or the other may be 
present : 

Polybasite . flg'g+gj 

_ . , ,.ZnS . Sb S„ , „,, AgS , SbS,, 

Fahlerze (4 Feg+As ^+2(4^+^) 

Chloride of silver, AgCl, 1794.3 or 143.79. — This salt contains in 100 
parts, 24.67 parts of chlorine, and 75.33 parts of silver. It is thrown down 
as a white precipitate, at first very bulky and curdy, when hydrochloric acid 
or a soluble chloride is added to any soluble salt of silver, except the hyposul- 
phite. It is wholly insoluble in water, and the most minute quantity of hy- 
drochloric acid contained in water may be detected by adding to it a drop of a 
solution of nitrate of silver. Hydrochloric acid, when concentrated, dissolves 
chloride of silver, which crystallizes from it in octohedrons, when the solution 
is evaporated. This salt dissolves easily in solution of ammonia, and crystal- 
lizes also as the ammonia evaporates. When heated, it fuses about 500°, 
forming a transparent yellowish liquid, which becomes, after cooling, a mass 
that may be cut with a knife and has considerable resemblance to horn; a pro- 



CHLORIDE OP SILVER. 461 

perty to which it was indebted for the name of horn silver, applied to it by 
the elder chemists. It is not volatile. Chloride of silver is not affected by a 
concentrated solution of potash. It is easily reduced to the state of metal by 
zinc or iron with water. Chloride of silver can be dissolved out in this way 
by means of zinc and acidulated water, from a porcelain crucible, in which it 
has been fused. The chloride and other salts of silver acquire a dark colour 
when exposed to light; chlorine escapes, and a portion of the salt appears to 
be reduced to the metallic state, as the blackened surface conducts electricity. 
According to Wetzlar, the black substance contains an inferior chloride of 
silver, and is not attacked by nitric acid, nor soluble in ammonia. Indeed, paper 
charged with chloride of silver is exceedingly sensitive to the impression of 
light, and has been employed to fix the image in the camera obscura. The 
unaltered chloride of silver in the paper, is afterwards dissolved out by a solu- 
tion of hyposulphite of soda. Of anhydrous chloride of silver, 100 parts ab- 
sorb 17.91 parts of ammoniacal gas, forming the compound 2AgCl-j-3NH 3 . 
This compound loses its ammonia in the air. Chloride of silver is dissolved 
by concentrated and boiling solutions of chlorides of potassium, sodium and 
ammonium, and, on cooling, a double salt is deposited in crystals generally 
cubes. Chloride of silver is also dissolved by cyanide of potassium, and the 
solution yields a double salt by evaporation, (Liebig.) 

Bromide of silver, AgBr. 2330 or 186.7. — This salt consists in 100 parts, 
of 41.99 bromine and 58.01 silver. It is insoluble in water, and falls as a 
precipitate which is at first white, but becomes of a pale yellow on collecting. 
When fused and cooled, it gives a mass of a pure and intense yellow. It is 
soluble in ammonia and has most of the properties of chloride of silver. 

Iodide of silver, Agl, 2931.1 or 234.87. — This salt consists in 100 parts, 
of 53.89 iodine and 46.11 silver. It is insoluble in water, like the chloride, 
but is distinguished from that salt by its colour, which is pale yellow, by the 
difficulty with which it is dissolved in ammonia, and by being blackened more 
slowly by the action of light. According to Martini, 2500 parts of ammonia, 
of density 0.960, are required to dissolve one part of iodide of silver. It is 
soluble to a large extent, at the boiling temperature in concentrated solutions of 
the alkaline and earthy iodides, and forms with them double salts. 

Cyanide of silver, AgCy, 1681.5 or 134.74. — This salt contains, in 100 
parts, 19.62 cyanogen and 80.38 silver. It falls as a white powder when hy- 
drocyanic acid is added to a solution of nitrate of silver. It is distinguished 
from chloride of silver by dissolving in concentrated nitric and sulphuric acids, 
when heated. It is readily decomposed by hydrochloric acid, and yields hy- 
drocyanic acid, 100 parts of cyanide of silver giving 20.36 parts of hydrocy- 
anic acid. It is decomposed by a red heat, and when well dried, gives nothing 
but cyanogen gas and silver. Cyanide of silver is dissolved by cyanide of 
potassium, and other soluble cyanides. The double cyanide of potassium and 
silver crystallizes in octohedrons, KCy-f-AgCy. 

Carbonate of silver, AgO,C0 2 , is a white insoluble powder. 

Sulphate of silver, AgO,S0 3 , 1952.8 or 156.48. — It is obtained by dis- 
solving silver with heat in concentrated sulphuric acid, or by precipitating a 
solution of nitrate of silver with sulphate of potash. It is soluble in 88 times 
its weight of boiling water, and crystallizes on cooling in the form of anhy- 
drous su4phate of soda. This salt is highly soluble in ammonia, and gives, 
by evaporation, an ammoniacal sulphate of silver in fine transparent crystals, 
which are persistent in air; AgO,S0 3 -f 2NH 3 . Chromate and seleniate of 
silver form analogous compounds with ammonia, which are all isomorphous. 
The bichromate of silver is also isomorphous with bichromate of soda. 

Hypo sulphate of silver, AgO, S.,O s , is soluble in water, and crystallizes ir 

39* 



462 SILVER. 

the same form as hyposulphate of soda. It crystallizes also with ammonia, 
as AgO,S 2 O s +2NH 3 . 

Hyposulphite of silver, AgO,S 2 2 . — Hyposulphurous acid appears to have 
a greater affinity for oxide of silver than for any other base. Oxide of silver 
decomposes the alkaline hyposulphites, and liberates one-half of their alkali, 
and a double hyposulphite of the alkali and silver is formed. These double 
salts are best prepared by adding chloride of silver in small portions to the so- 
luble hyposulphite of potash, soda, ammonia, or lime in the cold, till the liquid 
is saturated; after which the solution is filtered, and mixed with a large quan- 
tity of alcohol, which precipitates the double salt; those of potash and soda are 
crystallizable. Herschel considers the double salts obtained in this manner, 
as probably containing one eq. of hyposulphite of silver, to two eq. of the 
other hyposulphite. The solution of one of these double salts dissolves more 
oxide of silver, and forms a double salt, which is believed to contain single 
equivalents of the salts, and precipitates as a white crystalline, pulverulent 
bulky mass. The second compound is sparingly soluble in water, but dis- 
solves in ammonia, and communicates to the liquor an intensely sweet taste. 

The hyposulphite of silver itself, is an insoluble substance; it is prone to 
undergo decomposition, changing spontaneously into sulphate, and sulphuret of 
silver. When to a dilute solution of nitrate of silver, a dilute solution of hy- 
posulphite of soda is added by small quantities, a white precipitate of hypo- 
sulphite of silver falls, which dissolves again in a few seconds, from the for- 
mation of the soluble double hyposulphite of soda and silver. When enough 
of hyposulphite of soda has been gradually added, to render the precipitate 
permanent without, however, decomposing the whole silver salt, a flocculent 
mass is obtained of a dull gray colour, which is permanent. The liquor con- 
tains much hyposulphite of silver, and has an intensely sweet taste, not at all 
metallic; the silver is not precipitated from it by hydrochloric acid or the chlo- 
rides. An excess of hyposulphite of ^oda destroys the precipitated hyposul- 
phite of silver, converting it into sulphuret of silver. 

Nitrate of silver, AgO,N0 5 , 2128.6 or 170.57. — When a piece of pure silver 
is suspended in nitric acid, it dissolves for a time without effervescence at a 
low temperature, nitrous acid being produced, which colours the liquid blue; 
p i|s but if heat be applied or the temperature allowed to 

rise, then the metal dissolves with violent effer- 
vescence from the escape of nitric oxide. The ni- 
trate of silver crystallizes (fig. 115,) on cooling in 
colourless tables, which are anhydrous. It is solu- 
^\ m m:' / me * n * P art °f c °ld, in £ part of hot water, and in 4 

parts of boiling alcohol. The solution of this salt 
does not redden litmus paper, like most metallic 
salts, but is exactly neutral. Nitrate of silver fuses at 426° and forms a crys- 
talline mass on cooling; it is cast into little cylinders for the use of surgeons. 
It is sometimes adulterated in this state with nitrate of potash, which may be 
detected by the alkaline residue which the salt then leaves, when heated before 
the blowpipe, or with nitrate of lead, when the solution of, the salt is precipi- 
tated by iodide of potassium, of a full yellow colour. When applied to the 
flesh of animals, it instantly destroys the organization and vitality of the part. 
It forms insoluble compounds with many kinds of animal matter, and is em- 
ployed to remove it from solution. When organic substances, to which a 
solution of nitrate of silver has been applied, are exposed to light, they be- 
come black from the reduction of the oxide of silver to the metallic state. A 
solution of nitrate of silver in ether is employed to dye the hair black. It 
forms also the indelible marking ink used to write upon linen. The part of 
the linen to be marked should be first wetted with a solution of carbonate of 




SALTS OF SILVER. 463 

soda and dried, and the writing should be exposed to the light of the sun. For 
this ink, which is expensive, another liquid has been substituted by bleachers, 
namely, coal tar, made sufficiently thin with naphtha to write with* which is 
found to resist chlorine and to answer well as a marking ink. A strong solu- 
tion of nitrate of silver absorbs two equivalents of ammoniacal gas, and gives 
the crystallizable Ammoniacal nitrate of silver \ AgO,N0 5 -j-2NH 3 . The dry 
nitrate in powder absorbs three atoms of ammonia, NgO,N0 5 -f 3NH 3 . 

Nitrate of silver forms a double salt with nitrate of the red oxide of mer- 
cury, which crystallizes in prisms. Nitrate of silver and cyanide of mercury 
also form a double salt, when hot solutions of them are mixed; AgO,N0 5 -j- 
2HgCy + 8HO. Cyanide of silver is soluble in a boiling solution of nitrate of 
silver, and gives a crystalline compound, AgO,N0 5 -f 2AgCy, which is de- 
composed by water. 

Nitrite of silver, AgO,N0 3 1928.6 or 154.54. — Nitrate of soda is fused at 
a red heat, till it is wholly converted into nitrite by loss of oxygen; the latter 
salt then begins to lose nitrous acid, and a small portion of the salt dissolved 
in water will be found to precipitate silver brown. The fusion is then inter- 
rupted, the salt dissolved in boiling water, precipitated by nitrate of silver, 
and filtered while still very hot. The nitrite of silver, which requires 120 
times its weight of water at 60° to dissolve it, is precipitated as the solution 
cools. The other nitrites are prepared by rubbing this salt in a mortar with 
chlorides taken in equivalent quantities. It appears from experiments of 
Proust that two subnitrites of silver exist, one soluble and the other insoluble. 

Acetate of silver, which is soluble in 100 times its weight of cold water, is 
precipitated when acetate of copper is mixed with a concentrated solution 
of nitrate of silver. It crystallizes from solution in boiling water in anhydrous 
needles. 

Oxalate of silver is an insoluble powder. A double oxalate of potash and 
silver is formed by saturating binoxalate of potash with carbonate of silver. It 
is very soluble, and forms rhomboidal crystals, which are persistent in air. 

Peroxide of silver. — A superior oxide of silver is deposited upon the positive 
pole or zincoid of a voltaic battery in a weak solution of nitrate of silver, in the 
form of needles of 3 or 4 lines in length, which are black and have a metallic 
lustre, while metallic silver is, at the same time, deposited in crystals upon the 
negative pole or chloroid. The former crystals are converted by sulphuric acid 
into oxide of silver and oxygen, and yield with hydrochloric acid, chloride of 
silver and chlorine. 

Silver may be readily alloyed with most metals. It combines by fusion with 
iron, from which it cannot be separated by cupellation. Native silver is always 
associated with gold ; the two metals are found crystallized together in all pro- 
portions in the same cubic or octohedral crystals. Gold may be detected in a 
silver coin, by dissolving the latter in pure nitric acid, w T hen a small quantity of 
black powder remains, which after being washed with water, will be found to 
dissolve in nitro-muriatic acid, giving a yellow solution in which protochloride 
of tin produces a precipitate of the purple powder of Cassius. Pure silver, 
being very soft, is always alloyed in coin and plate, with a certain quantity of 
copper, to make it harder. The standard silver of England is an alloy of 222 
pennyweights, of silver with 18 pennyweights of copper. When the proportion 
of copper is considerable the alloy becomes red by wear, showing that the silver 
of the alloy yields more readily to attrition than the copper. This effect is very 
visible in the smaller silver pieces of some continental states. 



464 GOLD. 



SECTION IIL 

GOLD. 
Eq. 1243 or 99.6 ; Jiu (aurum.) 

Gold is found in small quantity in most countries, sometimes in iron pyrites, 
but generally native, massive and disseminated in threads through a rock, or in 
grains among the sand of rivers. It occurs crystallized in the cube and its 
allied forms. At present the principal supply of this metal is from the mines of 
South America, Hungary and of the Uralian mountains in Siberia. It is gene- 
rally separated from earthy and all other metallic substances, except silver, by 
amalgamation. It may be separated from silver by nitric acid, which dissolves 
the latter metal, but only when it forms a large proportion of the alloy. When 
nitric acid does not dissolve the silver, the alloy is submitted to an operation 
termed quart ation; it is fused with four times its weight of silver, after which 
the whole silver may be dissolved out by nitric acid. 

To obtain gold in a state of purity, the alloy containing it is dissolved in a 
mixture of two measures of hydrochloric, and one measure of nitric acid— a 
mixture which, from its application to dissolve gold has acquired the name of 
aqua regia. The solution of gold is evaporated by a water-bath, till acid vapours 
cease to be exhaled; it is then dissolved in water and hydrochloric acid is mixed 
with it. On adding protosulphate of iron to this solution, the gold is wholly 
precipitated as a brown or brownish yellow powder, quite destitute of the 
metallic lustre, which, however, appears when the powder is rubbed. The pro- 
tosulphate of iron is, at the same time, converted into persulphate and per- 
chloride : 

. 6(FeO,So 3 ) and Au 2 C] 3 =2(Fe 2 3 , 3S0 3 ) and Fe 2 Cl 3 and 2Au. 

Gold is the only metal of a yellow colour. When pure, it is more malleable 
than any other metal, and nearly as soft as lead. Its ductility appears to have 
scarcely a limit. A single grain of gold has been drawn into a wire 500 feet in 
length, and this metal is beaten out into leaves which have not more than 
1 -200,000th of an inch of thickness. The coating of gold on gilt silver wire is 
still thinner. When very thin, gold is transparent, thin gold leaf allowing a 
green light to pass through it. The point of fusion of this metal is 2016° ; it 
contracts considerably upon becoming solid. The density of gold varies from 
19.4 to 19.65, according as it has been more or less compressed. It does not 
oxidate or tarnish in air, at the usual temperature, nor when strongly ignited. 
But this and the other noble metals are dissipated and partly oxidated, when a 
powerful electric charge is sent through them in thin leaves. Gold is oxidated 
in contact with verifiable fluxes, and communicates to them a ruby colour. It 
is not dissolved by nitric, hydrochloric or sulphuric acid, nor indeed by any 
single acid. It is acted upon by chlorine, which converts it into perchloride, 
and by acid mixtures, such as aqua regia, which evolve chlorine. It combines 
in two proportions with oxygen, forming the two oxides Au 2 and Au 2 O s , 
neither of which combines with acids. 

Oxide of gold, Aurous oxide, Au 2 0, 2586 or 207.21.— This oxide is obtained 
by decomposing the corresponding chloride of gold, by a cold solution of potash, 
as a green powder. It is partly dissolved by the alkali, and soon begins to 
undergo decomposition, being resolved into the higher oxide and metallic gold. 
The latter forms a thin film upon the sides of the vessel, which is green by 
transmitted light, quite like gold leaf 



AUROUS COMPOUNDS. 465 

Chloride of gold, Jiurous chloride, Au 2 CI, is obtained by evaporating a solu- 
tion of the perchloride to dryness, and heating the powder thus obtained by a 
sand bath, retaining it about the temperature of melting tin and constantly 
stirring it, so long as chlorine is evolved. It is a white saline mass having a, 
tinge of yellow, which is quite insoluble in water. In the dry state, it is per- 
manent, but in contact with water it gradually undergoes decomposition, and 
is converted into gold and the perchloride. This change takes place almost 
instantaneously at the boiling temperature. 

A corresponding aurous sulphur et is formed when sulphuretted hydrogen 
gas is conveyed into a boiling solution of the perchloride of gold. It is dark 
brown, almost black. 

Peroxide of gold, Auric oxide, Au 2 3 , 2786 or 223.21. — This oxide has 
many of the properties of an acid. It is obtained by digesting magnesia in a 
solution of perchloride of gold, when an insoluble compound of auric oxide and 
magnesia is formed, which is collected upon a filter and well washed. The 
compound is afterwards digested in nitric acid, which dissolves the magnesia, 
with traces of auric pxide, but leaves the greater part of the latter undissolved. 
It is left in the state of a reddish-yellow hydrate, which dried in air becomes 
chestnut-brown. When precipitated by an alkali, auric oxide carries down a 
portion of the latter, of which it may be deprived by nitric acid. Dried at 212° 
it abandons its water, becomes black, and is in part reduced. When exposed 
to light, particularly to the direct rays of the sun, its reduction is very rapid. It 
is decomposed by an incipient red heat. Hydrochloric acid is the only acid 
which dissolves and retains this oxide, and then perchloride of gold is formed. 
It is dissolved by concentrated nitric and sulphuric acid, but precipitated from 
these solutions by water. Tho affinity uf this oxide for alkaline oxides is so 
great, on the contrary, that when boiled in a solution of chloride of potassium, 
auric oxide is dissolved, and the liquid becomes alkaline ; perchloride of gold 
with chloride of potassium, and uurate of potash, or a compound of auric oxide 
and potash, are formed. The compounds of auric oxide with the alkalies and 
alkaline oxides are nearly colourless, and are not decomposed by water. They 
appear to be of two different degrees of saturation, aurates which are soluble, 
and superaurates which are insoluble. The only one of these compounds which 
has been studied in some degree is the aurate of ammonia, or fulminating gold 
as it is named from its violently explosive character. 

Aurate of ammonia. — When the solution of gold is precipitated by a small 
quantity of ammonia, a powder of a deep yellow is obtained, which is a com- 
pound of aurate of ammonia with a portion of perchloride of gold. This com- 
pound is exploded by heat, but the detonation is not strong. But when the 
solution of gold is treated with an excess of ammonia, and the precipitate well 
washed by ebullition in a solution of ammonia, or better in water containing 
potash, the fulminating gold has a yellowish-brown colour with a tinge of purple. 
When dry, it explodes most easily with a loud report, accompanied by a feeble 
flame. It may be exploded by a heat a little above the boiling point of water, 
or by the blow of a hammer. Its composition has not been certainly determined, 
but if the ammonia is present in double the proportion that would contain the 
hydrogen necessary to burn the oxygen of the auric oxide* which Berzelius con- 
siders probable, its constituents may be Au 2 3 -f-2NH 3 -f HO. The affinity of 
auric oxide for ammonia is so great, that it takes that alkali from all acids. 
Thus, when auric oxide is digested in sulphate of ammonia, fulminating gold is 
formed, and the liquid becomes acid. 

Purple of Cassius. — When protochloride of tin is added to a dilute solu- 
tionof gold, a purple-coloured powder falls, which has received that name. It 
is obtained of a finer colour, when protochloride of tin is added to a solution 
of the perchloride of iron, till the colour of the liquid has a shade of green. 



466 GOLD. 

and adding this liquid, drop by drop, to a solution of perchloride of gold 
which is free from nitric acid, and very dilute. After 24 hours, a brown 
powder is deposited, which is in a small degree transparent and purple-red by 
transmitted light. When dried and rubbed to powder, it is of a dull blue co- 
lour. Heated to redness it loses a little water, but no oxygen, and retains its 
former appearance. If washed with ammonia on the filter while still humid, 
it is dissolved, and a purple liquid passes through, which rivals the hyper- 
manganate of potash in beauty. From this liquid, the colouring matter very 
gradually separates, weeks elapsing before the upper strata of the liquid be- 
come colourless, but it is precipitated more rapidly when heated in a close 
vessel between 140° and 180°. The powder of Cassius is insoluble in 
solutions of potash and soda. It may also be formed, by fusing together 2 
parts of gold, 3| parts of tin and 15 parts of silver, under borax, to prevent 
the oxidation of the tin, and treating the alloy with nitric acid to dissolve out 
the silver; a purple residue is left containing the tin and gold that were em- 
ployed. 

The powder of Cassius is certainly, after ignition, a mixture of peroxide 
of tin and metallic gold, from which the last can be dissolved out by aqua 
regia, while the peroxide of tin is left ; and the last mode of preparing it, 
favours the idea that its constitution is the same before ignition. But its pro- 
perty to dissolve in ammonia, and the fact that mercury does not dissolve out 
gold from the powder when property prepared, appear to me to be conclusive 
against that opinion. The proportions of its constituents vary so much, that 
there must be more than one compound, or more likely the colouring com- 
pound combines with more than one proportion of peroxide of tin. Berzelius 
proposes the theory that the powder of Cassius may contain the true protoxide 
of gold combined with the deutoxide of tin, AuO-fSn 2 3 , a kind of combina- 
tion containing an association of three atoms of metal, which is exemplified 
in black oxide of iron, spinell, gahnite, franklinite and other minerals, and 
which we have repeatedly observed to be usually attended with great stability. 
A glance at its formula shows how readily the powder of Cassius, as thus re- 
presented, may pass into gold and peroxide of tin; AuO + Sn 2 3 = Au and 
2Sn0 2 . The existence of a purple oxide of gold AuO is not established, but 
it is probably the substance formed when a solution of gold is applied to the 
skin or nails, and which dies them purple. Paper-coloured purple by a solu- 
tion of gold becomes gilt when placed humid in phosphuretted hydrogen gas, 
which reduces the gold to the metallic state. 

Sesquisulpliuret of gold, Au 2 S 3 , or the auric sulphuret, is formed when 
a dilute solution of gold is precipitated cold by sulphuretted hydrogen. It is 
a flocculent matter of a strong yellow colour, which becomes deeper by dry- 
ing; it loses its sulphur at a moderate heat. 

Sesquichloride of gold, Perchloride of gold, Auric chloride, Au 2 Cl 3 , 3814 
or 305.62. — It is formed when gold is dissolved in aqua regia. The solution 
is yellow, and becomes paler with an excess of acid, but is of a deep red when 
neutral in composition. It is obtained in the last condition by evaporating 
the solution of gold, till the liquid is of a dark ruby-red colour, and begins to 
emit chlorine. It forms on cooling a dark red crystalline mass, which deli- 
quesces quickly in air. But to procure the auric chloride perfectly free from 
acid salt, the only mode is to decompose the aurous chloride with water. A 
compound of chloride of gold and hydrochloric acid crystallizes easily from 
an acid solution, in long needles of a pale yellow, which are permanent in 
dry air, but run into a liquid in damp air. The solution of this salt deposites 
gold on its surface, and on the side of the vessel turned to the light. The 
gold is also precipitated in the metallic state by phosphorus, by most metals, 
the ferrous salts, and many vegetable and animal substances, by vegetable 



PLATINUM. 467 

acids, by oxalate of potash, when carbonic acid escapes. Chloride of gold is 
soluble in ether and in some essential oils. It forms double salts with most 
other chlorides, which are almost all orange when crystallized; in efflorescing, 
they become of a lemon-yellow, but in the anhydrous state they are of an 
intense red. They are obtained by evaporating the mixed solutions of the 
two salts. 

Chloride of gold and potassium, KCl-f-Au 2 Cl 3 -f 5HO. — It crystallizes in 
striated prisms of right summits, or in thin hexagonal tables which are very 
efflorescent ; this salt becomes anhydrous at 212°. The anhydrous salt fuses 
readily when heated, but loses chlorine and becomes a liquid, which is black 
while liquid, and yellow when cold. It is then a compound of the aurous chlo- 
ride with chloride of potassium. Chloride of gold and ammonium crystallizes 
in transparent prismatic needles, which become opaque in air, Mr. Johnston 
found their composition to be NH 4 Cl+Au 2 Cl 3 +2HO. Chloride of gold and 
■sodium crystallizes in Jong four-sided prisms, and is persistent in air. Its com- 
position is NaCI-j-Au 2 Cl 3 -f-4HO. Bonsdorff has prepared similar double salts 
with chlorides of barium, strontium, calcium, magnesium, manganese, zinc, 
cadmium, cobalt and nickel. The salt of lime contains six and the salt of mag- 
nesia twelve atoms of water. 

Sesquibromide of gold, Au 2 Br 3 , is formed by dissolving gold in a mixture 
of nitric and hydrobromic acids. It greatly resembles the sesquichloride, and 
forms also an extensive series of double salts. 

The aurous iodide, Au 2 I, is formed when hydriodic acid is digested upon 
peroxide of gold, iodine being, at the same time, liberated. It is a lemon-yellow 
crystalline powder, insoluble in cold water, and soluble with great difficulty in 
boiling water. 

The only salt with an oxygen acid, which peroxide of gold appears to form 
is the fulminate, and, perhaps, a seleniate. 



ORDER IX. 

METALS IN NATIVE PLATINUM. 

SECTION I. 

PLATINUM. 

Eq. 1233.5 or 98.84; Pt. 

This metal was discovered in the auriferous sand of certain rivers in America, 
Its name is a diminutive of plat a, silver, and was applied to it on account of its 
whiteness. It occurs in the form of rounded or flattened grains of a metallic 
lustre. It has been found in Brazil, Colombia, Mexico, St. Domingo, and on 
the eastern declivity of the Ural chain ; it is every where associated with the 
debris of a rock easily recognised as belonging to one of the earliest volcanic 
formations. 

The grains of native platinum contain from 75 to 87 per cent, of that metal, 
so much iron that they are generally magnetic, from J to 1 per cent, of palla- 
dium, but sometimes much less, with small quantities of copper, rhodium, 



468 PLATINUM. 

osmium and iridium. To separate the platinum from these bodies, the ore is 
digested in a retort with hydrochloric acid, to which additions of nitric acid are 
made from time to time. When the hydrochloric acid is nearly saturated, the 
liquid is evaporated in the retort to a syrup, then diluted with water and drawn 
off from the insoluble residue. If the mineral is not completely decomposed, 
more aqua regia is added and the distillation continued. A portion always 
remains undissolved, consisting of grains of a compound of osmium and iridium, 
and little brilliant plates of the same alloy, besides foreign mineral substances 
which maybe mixed with the ore. The solution is generally deep red, and 
emits chlorine from the presence of perchloride of palladium ; to decompose 
which, the liquid is boiled, chlorine escapes, and the palladium is reduced to 
protochloride. Chloride of potassium is then added, which precipitates the 
platinum as a sparingly soluble double chloride of platinum and potassium, of 
which the colour is yellow, but red if it is accompanied by the double chloride 
of iridium and potassium. The precipitate is collected on a filter, and washed 
with a dilute solution of chloride of potassium. By igniting this double salt 
with twice its weight of carbonate of potash to the point of fusion, the platinum 
is reduced to the metallic state, while a portion of the iridium remains as 
peroxide. The platinum is dissolved by aqua regia in which the peroxide of 
iridium remains untouched. To complete the separation of the iridium, the 
precipitation, by chloride of potassium and ignition with carbonate of potash, 
may require to be repeated several times. But when it is not required to have 
platinum absolutely pure, the solution of the ore is precipitated by sal-ammoniac, 
and it is in this way that much of the commercial platinum is procured, the inso- 
luble double chloride of platinum and potassium is washed with a solution of 
sal-ammoniac dried and heated to low redness ; hydrochloric acid and nitrogen 
-escape and sal-ammoniac sublimes, while the platinum remains behind as a 
pulverulent mass, or spongy and a little coherent. The small trace of iridium 
which is left in commercial platinum increases greatly its hardness and tenacity. 

Platinum is too refractory to be fused in our furnaces, but at a high tempe- 
rature, its particles cohere like those of iron, and it may, like that metal, be 
welded. Hence, by heating a mass of spongy platinum, previously strongly 
compressed, and submitting it to increasing pressure, the mass comes to be 
so far compacted, that it may be forged with a hammer. Platinum as it comes 
from the hands of the workman is highly malleable and ductile. It is the 
densest body at present known; the specific gravity of platinum was fixed by 
Dr. Wollaston at 21.53. This metal may be fused by the oxihydrogen blow- 
pipe, or even made to boil, and be dissipated with scintillations. It is not 
acted upon by any single acid, not even by concentrated and boiling sulphuric 
acid. Its resistance to the action of acids, conjoined with its difficult fusibility 
renders platinum invaluable for chemical experiments, and for some purposes 
in the chemical arts, particularly for the concentration of oil of vitriol. 

The remarkable influence of a clean surface of platinum in determining the 
combustion of oxygen and hydrogen, has already been considered. This 
property platinum shares with osmium, iridium, palladium and rhodium. It 
is exhibited in the greatest degree by the highly divided metal, such as plati- 
num sponge, the condition in which the metal is left on igniting the double 
chloride of platinum and ammonium. Platinum precipitated from solution by 
zinc, causes the combustion of alcohol vapour. The black powder of platinum 
is the form in which that metal is most active. This is prepared by dis- 
solving the protochloride of platinum in a hot and concentrated solution of 
potash, and pouring alcohol into it while still hot, by small quantities at a 
time; a violent effervescence occurs from the escape of carbonic acid gas, by 
which the contents of the vessel, unless capacious, may be thrown out. The 
liquor is decanted from the black powder which appears, and the latter boiled 



PLATINUM. 469 

successively with alcohol, hydrochloric acid and potash, and finally four or 
five times with water, to divest it of all foreign matters. The powder, when 
dried, resembles lamp black, and soils the fingers, but still it is only metallic 
platinum extremely divided, and may be heated to full redness without any 
change of appearance or properties. It loses these, however, by the effect of 
a white heat, and assumes a metallic aspect. The powder of platinum, like 
wood charcoal, absorbs and condenses gases, in its pores, with the evolution 
of heat, a property which must assist its action on oxygen and hydrogen, al- 
though not essential to that action. When moistened with alcohol, it deter- 
mines the oxidation of that substance in air, and the formation of acetic acid. 

Platinum is insoluble in all acids, except aqua regia. It may be oxidated in 
the dry way by fusing it with hydrate of potash or nitre. Palladium, osmium 
and iridium resemble platinum in their chemical relations, the corresponding 
compounds of these four metals being isomorphous; platinum and iridium have 
also the same atomic weight. Of platinum, only two decrees of oxidation are 
known with certainty, the protoxide, PtO, and peroxide Pt0 2 . 

Protoxide, of platinum, Platinous oxide, PtO, 1333.5 or 106.84. — It is ob- 
tained by digesting the corresponding chloride of platinum with potash, as a 
black powder, which is a hydrate. This oxide is dissolved by the excess of 
alkali, and forms a green solution, which may become black like ink with a 
large quantity of oxide. Protoxide of platinum forms the platinous class of 
salts, which have a greenish, or sometimes red colour, and are distinguished 
from the platinic salts by not being precipitated by sal-ammoniac. 

Sulphuret of 'platinum , PtS, is thrown down as a black precipitate, when 
the protochloride of platinum is decomposed by sulphuretted hydrogen. It 
may be washed and dried without decomposition. 

Protochloride of platinum, PtCl, is obtained by evaporating a solution of 
the bichloride of platinum to dryness; triturating the dry mass and heating it 
in a porcelain capsule, by a sand bath at the melting point of tin, taking care 
to stir it, at the same time, so lon^ as chlorine is evolved. It remains as a 
greenish gray powder, quite insoluble in water, and repelling that liquid so as 
not to be moistened by it. This chloride is not decomposed by sulphuric or 
nitric acid, but is partially soluble in boiling and concentrated hydrochloric 
acid. From the last solution, alkalies throw down a black precipitate of pro- 
toxide. When the calcination of the bichloride of platinum, at 420° or 460°, 
is interrupted before the whole chlorine is expelled, the residue gives to water 
a compound of a brown colour, so deep, that the liquid becomes opaque. 
This, Professor Magnus believes to be a combination of the two chlorides of 
platinum. A double protorhlnri.de of platinum and potassium, PtOl-f-KCl is 
obtained on adding chloride of potassium to the solution of the platinous chlo- 
ride in hydrochloric acid, and evaporating the liquid. The salt crystallizes 
in four*sided red prisms, of which the form is the same as a corresponding- 
salt of palladium; it is anhydrous. A protochloride of platinum and sodium 
also exists, but does not crystallize easily. 

Ammoniacul protochloride of platinum, PtCl-f NH 3 , was obtained by Mag- 
nus, on adding solution of ammonia to the double protochloride of platinum 
and ammonium. A green salt precipitates after a time, which is entirely crys- 
talline, insoluble in water, alcohol, hydrochloric acid and ammonia. 

The green crystalline salt of Magnus is not decomposed or dissolved by 
boiling alkalies, nor by boiling sulphuric or hydrochloric acid; so that the am- 
monia or its elements are in an unusual state of combination. M. J. Gros, of 
Wesserling, has formed a singular class of compounds from it. When treated 
with hot concentrated nitric acid, the green salt is converted into a white crys- 
talline powder, which dissolves easily in water, leaving half the platinum in 
the metallic state. The white salt is obtained by a second crystallization in 
40 



470 PLATINUM. 

Hat prisms; it is named nitrate of the chlordmide of platinum by Liebig* 
Neither the chlorine nor the platinum contained in this salt is precipitated 
by the usual reagents. When a hot saturated solution of this salt is mixed 
with sulphate of soda, a corresponding sulphate of less solubility is deposited 
in small needles. A hydrochlorate is also obtained by adding hydrochloric 
acid to a boiling solution of the nitrate or sulphate, which crystallizes on cool- 
ing in octohedral crystals. By mixing a solution of the nitrate with a soluble 
oxalate, phosphate, tartrate, citrate, malate and saccharate, compounds of these 
acids with the same base were produced, which are all crystallizable and less 
soluble in the cold than in the nitrate.* 

These salts are represented as containing a substance Pt,ClN„H 6 , of the 
same character as ammonium: 

Hydrochlorate \ > . Pt,ClN 2 H 6 -f CI 

Nitrate .... Pt,ClN 2 H 6 + N0 5 , 

Sulphate .... Pt,ClN 2 H 6 + S0 3 . 

Oxalate .... Pt,ClN 2 H 6 0+C 2 6 3 . 

M. Liebig also suggests another view, that these salts contain a salt of pla* 
tinum, analogous to the bichloride, but in which the second atom of chlorine 
is replaced by amidogen, that is Pt-fCl.NH 2 . This salt is combined with 
chloride of ammonium, in the hydrochlorate; which thus becomes analogous 
to the bichloride of platinum and potassium, of which the new salt has the 
form. The nitrate, sulphate, and oxalate are compounds of nitrate, sulphate 
and oxalate of ammonia with the same salt Pt-f-Cl,NH 2 . This last view, 
which is so simple, is opposed by the fact that neither chlorine nor platinum 
is precipitated from these salts by the usual reagents. But this, I think, is not 
a sufficient ground for its rejection, considering how little many admitted 
double salts are affected by the reagents which precipitate the salts individually 
before their combination, such, for instance* as the double oxalate of chromium 
and potash. 

Corresponding platinous iodides and cyanides have been formed. The 
platinous oxide has also been united with several acids, particularly sulphuric, 
nitric, oxalic and acetic acids; but none of these salts has been crystallized, ex* 
cept the oxalate. 

Peroxide of platinum, Platinic oxide, Pt0 2 , 1433.5 or 114.84. — By preci- 
pitating sulphate of platinum with nitrate of barytes, nitrate of platinum is ob- 
tained. One half of its oxide may be precipitated by soda, from the last salt, 
but when a larger quantity of alkali is added, a subsalt is thrown down. 
The precipitated oxide is hydrated, very bulky and resembles perfectly per- 
oxide of iron precipitated by ammonia. When heated, it first loses its water, 
and becomes black, then its oxygen, and leaves metallic platinum. Peroxide 
of platinum combines with acids, and forms a class of salts, which are either 
yellow or reddish-brown. It has also a decided affinity for bases, and forms 
insoluble compounds with the alkalies, earths and many metallic oxides. It 
forms also, like peroxide of gold, a fulminating ammoniacal compound, disco- 
vered by Mr. E. Davy. 

Bisulphuret of platinum, PtS 2 , is formed by adding a solution of bichloride 
of platinum, drop by drop, to a solution of sulphuret of potassium. It is dark- 
brown and by desiccation becomes black. When dried in open air, a portion 

* Gros, Ari. de Ch. et de Ph. t. 69, p. 204. 



PALLADIUM. 471 

of its sulphur is converted into sulphuric acid, by the absorption of oxygen, 
and the mass becomes strongly acid. 

Bichloride of platinum, PtCl 2 ; 2119 or 169.78. — Is obtained by concen- 
trating the solution of platinum in aqua regia, as a red saline mass, which be- 
comes brown when deprived of its water of crystallization by heat. The 
solution of this salt when pure, is an intense and unmixed yellow; the red 
colour which it usually exhibits being due to iridium or to protochloride of 
platinum. Bichloride of platinum is soluble in alcohol, and the solution is 
used to separate potash in the analysis of a salt. The salt being first ignited, 
to expel ammonia, is dissolved in a minimum of water, and the solution mixed 
with chloride of platinum, a yellow granular precipitate falls, if the salt con- 
tains potash, which may be washed with diluted alcohol, and dried. One 
hundred parts of this salt are equivalent to 19.33 parts of potash, and to 
40.39 of platinum. 

Chloride of platinum and potassium, KCl-f PtCl 2 , is the salt which falls 
on mixing chloride of platinum with chloride of potassium or any other salt of 
potash. The crystalline grains of which it is composed are regular octohe- 
drons. This salt is soluble to a certain extent in water, but is wholly inso- 
luble in alcohol. It is anhydrous. A very intense bright red-heat is required 
for its complete decomposition. The double chloride of platinum and sodium, 
NaCl-f-PtCl 2 -f 6HO, crystallizes in beautiful transparent prisms of a bright- 
yellow colour. It is soluble in alcohol as well as in water. When a solution 
of this salt in alcohol is distilled till only one-fourth of the liquid remains, the 
solution when evaporated gives a salt containing the elements of ether, be- 
longing to a class of compounds discovered by Professor Zeise, and known as 
the etherized salts of Zeise. The chloride of platinum and ammonium re- 
sembles the double salt of potassium. BonsdorfT has formed a large class of 
compounds of bichloride of platinum with the alkaline, earthy and metallic 
chlorides, in all of which the salts are united in single equivalents. The 
bromides and iodides of platinum have likewise been formed, and classes of 
double salts derived from them. Peroxide of platinum has also been com- 
bined with acids, but none of its salts, with the exception of the oxalate, ob- 
tained in a crystalline state. 



SECTION II. 

PALLADIUM. 

Eq. 665.9 or 53.36 ; Pd. 

This metal was discovered in 1803, by Dr. Wollaston. It is precipitated 
from the solution of the ore of platinum, after the removal by sal-ammoniac 
of that metal, by a solution of cyanide of mercury, and is gradually deposited 
as a yellowish white flocculent powder, which is cyanide of palladium, and 
yields the metal when calcined. 

In external characters, palladium closely resembles platinum. It is nearlv 
as infusible, but can more easily be welded. The density of the fused metal 
is 11.3; after being laminated 11.8. At a certain temperature, the surface of 
palladium tarnishes and becomes blue from oxidation, but when more strongly 
heated, the oxide is reduced. It is very slightly attacked by boiling and con- 
centrated hydrochloric and sulphuric acids. Palladium dissolves in nitric 
aoid, communicating a brownish-red colour to the acid, while no gas is 



472 PALLADIUM. 

evolved if the temperature is low, the nitric acid decomposed being converted 
into nitrous acid. Palladium dissolves with facility in aqua regia; its surface is 
blackened by the tincture of iodine, which has no effect upon platinum. This 
metal has a considerably greater affinity for oxygen than platinum. It forms 
two oxides, the protoxide of palladium PdO, and the peroxide Pd0 2 . 

Protoxide of Palladium, Palladous oxide, PdO, 765.9 or 61.36. — This oxide 
is obtained by dissolving palladium in nitric acid, evaporating the solution to 
dryness, and calcining the nitrate by a gentle heat. It forms a black mass, 
which dissolves with difficulty in acids. When carbonate of potash or soda is 
added in excess to a palladous salt, the hydrated protoxide precipitates of a 
very dark-brown colour. This oxide is easily deprived of its water by heat, 
but a violent calcination is necessary to. reduce it to the metallic state. 

Prolo sulphur el of palladium, PdS, is obtained by precipitation of a palladous 
salt by sulphuretted hydrogen, and is of a dark-brown colour, or is prepared 
by the direct union of its elements. 

Protochloride of palladium, PdCl, is prepared by dissolving palladium in 
hydrochloric acid, to which a little nitric acid is added, and evaporating the 
solution to dryness, to expel the excess of acid. The compound is a mass of a 
dark-brown colour, which becomes black when made anhydrous by heat, and 
may be fused in a glass vessel. When heated in platinum vessels it becomes 
contaminated by the protochloride of that metal. When dissolved with chloride 
of potassium, it forms a double salt, KCl-f PdCl, which is soluble in cold, and 
considerably more so in hot water, and crystallizes in four-sided prisms, of a 
dull yellow. Protochloride of palladium also combines with chloride of ammo- 
nium and chloride of sodium, and forms double salts, according to BonsdorfT, 
with most other chlorides. Protochloride of palladium forms two ainmoniaca! 
compounds; one of which is insoluble, greenish-yellow and anhydrous, PdCl -f- 
NH 3 . 

Prolo cyanide of palladium, PdCy, is always formed when cyanide of mer- 
cury is added to a neutral solution of palladium, as a light coloured precipitate 
which becomes gray after drying, W r hen the solution of palladium is acid no 
precipitate is formed, and when the solution contains copper, the precipitate has 
a green colour. Palladium appears to have a greater affinity for cyanogen 
than any other metal. The cyanide of mercury even is decomposed when 
boiled with protoxide of palladium, and cyanide of palladium formed. When 
this cyanide is dissolved in ammonia, and the excess of the latter allowed to 
escape by evaporation, a precipitate of brilliant, colourless, crystalline plates is 
formed, which appears to be ammoniacal cyanide of palladium. 

Nitrate of palladium, PdO,N0 5 , is formed»by dissolving the metal in nitric 
acid ; the solution dries up into a dark-red saline mass. When an excess of 
ammonia is added to this salt, and the solution evaporated by a gentle heat, a 
colourless ammoniacal nitrate is deposited in rectangular tables. 

Peroxide of palladium, Palladic oxide, Pd0 2 , 8,65.9 or 69.36. — To prepare 
this oxide, Berzelius recommends a solution of the hydrate or carbonate of 
potash to be added, by small quantities at a time, to the dry bichloride of palla- 
dium and potassium, mixing well after each addition. A yellowish brown 
powder separates, which is the hydrated peroxide, retaining a little alkali. 
Washed with boiling water, it loses the greater part of its combined water and 
becomes black. This oxide dissolves with difficulty in acids; the solutions are 
yellow. The corresponding bisulphuret of palladium has not been formed. 

Bichloride of palladium, PdCl 2 , is obtained in solution, when protochloride 
is dissolved in concentrated aqua regia, and the solution only slightly heated. 
It forms a solution of so dark a brown as to appear black, which gives a red 
precipitate with chloride of potassium, When the solution is diluted or heated, 



IRIDIUM. 473 

chlorine gas is evolved, and protochloride of palladium reproduced. The double 
salt of this chloride and chloride of potassium is obtained by treating the double 
protochloride of palladium and potassium in fine powder with aqua regia, and 
evaporating the supernatant fluid to dryness. It forms a cinnabar red powder, 
in which little octohedral crystals can be perceived, both the palladic and pal- 
ladous double chlorides being isomorphous with the corresponding compounds 
of platinum. When treated with hot water, this double salt emits chlorine, and 
is in a great measure decomposed. The salts of the peroxide of palladium are 
scarcely known. 

SECTION III. 

IRIDIUM AND OSMIUM. 
IRIDIUM. 

Eq. 1233.5 or 98.84; Ir. 

The black scales which remain when native platinum is dissolved in aqua 
regia, were discovered by Mr. Smithson Tennant to contain these metals (Phil. 
Trans. 1804.) The same alloy occurs in flat white metallic grains in native 
platinum. Iridium has also been observed in combination with about 20 per 
cent, of platinum, crystallized in octohedrons, which are whiter than platinum, 
and are said to have a greater density, namely 22.66. Osmium and iridium 
are separated from each other, with considerable difficulty, by processes for 
which I must refer to the memoir of Wollaston (Phil. Trans. 1829, p. 8,) or to 
Berzelius, (Traite, t. I, p. 415.) 

Iridium is obtained immediately from the chloride, by decomposing that salt 
with hydrogen at a gentle heat, or by exposing it alone to a very high tempera- 
ture, in the form of a gray metallic powder, much resembling spongy platinum. 
It is one of the most refractory bodies known, not being fused by the oxihydro- 
gen blow pipe. Mr. Children, however, succeeded in fusing a portion of iridium 
into a globule, by the discharge of a very large voltaic battery. This globule 
was white and very brilliant, but still a little porous; its density was 18.68.* 
Iridium becomes white and brilliant by strong ignition, without fusion, and is 
afterwards insoluble in acids. If reduced by hydrogen at a low temperature, 
it oxidates slowly when heated to redness, or when digested in aqua regia. 
This metal is generally rendered soluble by one or other of the following ope- 
rations. It is calcined with hydrate of potash or nitre, or with a mixture of 
these salts, which gives a compound of deutoxide of iridium and potash. Or, 
the metal is reduced to a fine powder and intimately mixed with an equal weight 
of chloride of potassium or sodium, and the mixture heated to low redness in a 
stream of chlorine gas. The metal then combines with chlorine, and the double 
chloride of iridium and potassium or sodium is formed, which is soluble in water. 

Oxides of iridium. — Iridium forms four compounds with oxygen, which are 
obtained by decomposing the corresponding chlorides. The protoxide of 
iridium, IrO, is obtained from the chloride produced when iridium is heated in 
chlorine gas. Also by precipitating the double chloride of iridium and potassium 
(KCl + IrCl) by carbonate of potash. The hydrate is then obtained of a greenish 

[* Professor Hare has succeeded by means of his oxyhydrogen blow pipe in fusing speci- 
mens of iridium of undoubted purity. The largest mass obtained weighed sixty-seven 
grains, was solid throughout and of a pale brilliant white, its specific gravity as ascertained 
by accurate experiments was 21.8; thus establishing for iridium a pre-eminence in density 
over platinum and all other bodies. Proceedings of the Am. Phil. Soc, May and June, 
1842. R. B.] 

40* 



474 OSMIUM,. 

gray colour, which is soluble in an excess of the alkaline carbonate. This oxide 
is the base of a class of salts. The deutoxide of iridium, lr 2 3 , is formed when 
the metal is calcined with hydrate of potash or nitre, and is the state of oxidation 
which iridium most readily assumes. Berzelius recommends as the best pro- 
cess for procuring it, to mix the double bichloride of iridium and potassium (K 
Cl-f-IrCl 2 ) with twice its weight of carbonate of potash, and to expose it to a 
low red heat. On dissolving out the alkaline salt, the deutoxide remains as a 
very line powder, of a black colour with a shade of blue. A heat above the 
melting point of silver is required to expel the oxygen from this oxide. It is 
reduced to the metallic state by hydrogen gas at the usual temperature, which 
appears to arise from the oxide of iridium having the property, as well as the 
metal, to determine the oxidation of hydrogen, a reaction which causes the 
oxide to be heated to the temperature at which it is itself reduced by hydrogen. 
The hydrate of this oxide dissolves in acids and forms a particular class of salts. 
of which the solutions are sometimes of a very dark colour, resembling a 
mixture of water and venous blood. B'moxide of iridium, or iridic oxide, 
Ir0 2 , has not been obtained in a separate state, but exists in a class of salts, 
from which this oxide is not precipitated by an alkali. Peroxide of iridium, 
Ir0 3 , or susiridic oxide, is formed in small quantity when the alloy of osmium 
and iridium fused in nitre is digested in aqua regia. The double perchloride 
of iridium and potassium then formed yields a rose-red solution. The salts of 
the protoxide and peroxide afford blue and purple solutions when mixed, de- 
pending probably on the formation of one or more combinations of these oxides. 
The name iridium (from Iris) was applied to this metal, from the variety of 
colours which its preparations exhibit. 

Sulphurets of iridium corresponding with the oxides of the same metal have 
been formed. 

Chlorides of iridium. — The protochloride, IrCl, is formed when iridium in 
powder is heated to low redness in chlorine gas. As thus prepared it is inso- 
luble in water, but slightly soluble in hydrochloric acid. It forms double salts 
with chlorides of potassium, ammonium and sodium. The sesquichloride, Ir 2 
CI 3 , also forms double salts, but which are not crystallizable. The bichloride 
of iridium forms a double salt with chloride of potassium, in brilliant black octa- 
hedral crystals, corresponding with the bichloride of platinum and potassium. 
The bichloride of iridium and sodium is also isomorphous with the correspond- 
ing platinum salt. 

Carburet of iridium,. — When a coherent mass of iridium is held in the 
flame of a spirit lamp, black masses appear on its surface, which are a carbu- 
ret, containing 19.83 per cent, of carbon, or IrC 4 , The carbon burns off 
readily in the air. 

OSMIUM. 

Eq. 1244.5 or 99.72; Os. 

In the treatment of the alloy of iridium and osmium, the latter is separated 
as a volatile oxide, or osmic acid. To obtain the metal, a solution of osmic 
acid is mixed with hydrochloric acid, and digested with mercury in a well 
closed bottle at a temperature of 104° (40° cent.) The osmium is reduced 
by the mercury, and an amalgam formed, which is distilled in a retort till all. 
the mercury and calomel formed are removed: osmium remains as a black 
powder without metallic lustre. When rendered coherent, osmium is a white 
metal, less brilliant than platinum, and very easily pulverized. Its density ie 
about 10. As obtained from the amalgam, osmium is highly combustible, 
when a mass of it is ignited at a point, it continues to redden, and burno 



osmium. 475 

without residue, being converted into the volatile oxide or osmic acid. Os- 
mium in the same condition is oxidated by nitric acid or aqua regia, and the 
osmic acid formed distils over with the water and acid. But after being 
exposed to a red heat, osmium becomes much less combustible in air, and is 
not oxidated by the humid way, resembling silicon and titanium in- that re- 
spect. Five different oxides of this metal are enumerated, but osmic acid is 
the only one of these which is formed directly; the others are obtained by the 
decomposition of corresponding chlorides. The three lowest of these oxides 
are analogous in composition to the oxides of iridium. 

Chlorides and oxides of osmium. — When osmium is heated in a long glass 
tube by a spirit lamp and chlorine gas passed over it, two chlorides are 
formed, which condense separately in the tube, owing to a difference in 
their volatility. The prolochloride, OsCl, which is the least volatile, crys- 
tallizes in needles of a deep green colour. It is deliquescent, and forms a 
green solution remarkable for its beauty. This solution is instantly dis- 
coloured by great dilution, metallic osmium is deposited, and hydrochloric 
and osmic acids remain in solution. Chloride of osmium combines with 
alkaline chlorides, and acquires greater stability. The protoxide is obtained 
by adding potash to a solution of this double salt; after some hours, a deep 
green, almost black, powder is precipitated, which is the hydrated oxide. 
This hydrate contains alkali. It dissolves slowly but completely in acids, 
and gives solutions of a deep green colour. 

Deutoxide of osmium, Os 2 0,,, is obtained by heating a solution of the os- 
miate of ammonia to 100° or 140°, when nitrogen gas is disengaged and deu- 
toxide deposited. The oxide contains ammonia. It dissolves slowly in acids, 
and forms yellowish-brown solutions, which become of a brown-black when 
they contain much oxide. The metal is not precipitated from these solutions 
by zinc or iron. The corresponding sesquichloride of osmium is obtained in 
combination with chloride of potassium, as a double salt, when the preceding 
oxide containing ammonia is dissolved in hydrochloric acid, and evaporated 
to dryness; the compound is not crystalline. 

Bichloride of osmium, OsCl 2 , is the more volatile chloride produced when 
osmium is heated in chlorine. It condenses as a dark red iloury powder. 
Exposed to air, it attracts a little moisture, and forms dendritic crystals. This 
salt is soluble in little water, giving a yellow solution, but is decomposed by 
a large quantity, like the protochloride. The bichloride of osmium and po- 
tassium is prepared in the same manner as the corresponding salt of iridium. 
In powder, it is of a red colour like minium, but forms also the usual octohe- 
dral crystals, KCl + OsCl 2 , which are brown. A solution of this double salt, 
mixed with carbonate of potash or soda, affords after a time, or immediately, 
if heated, the corresponding peroxide of osmium, 0s0 o , as a brown powder, 
which appears black when collected. It is a base capable of uniting with 
acids at the moment of its formation. This oxide like the peroxide of iridium 
is reduced by hydrogen at the usual temperature. 

Osmic acid, Os0 4 , or the volatile oxide of osmium is best obtained by the 
combustion of osmium in a glass tube through which a stream of oxygen gas 
is passed. It condenses in long colourless, regular prismatic needles. The 
odour of this compound is extremely acid and penetrating, resembling that of 
the chloride of sulphur. It was from this property of its acid, which is so con- 
stantly observed when the oxidable compounds of osmium are heated in air, 
that osmium obtained its name (from o<ry.t<r odour.) Its taste is acrid and 
burning, but not acid. It becomes soft like wax by the heat of the hand, 
melts into a colourless liquid like water considerably below 212°, and enters 
into ebullition a very little above its point of fusion. It is dissolved slowly, 
but in considerable quantity, by water. The solution has no acid reaction. 



476 RHODIUM. 

Osmic acid is also soluble in alcohol and ether, but these solutions are apt to 
deposite metallic osmium. It is a weak acid, being incapable of displacing 
carbonic acid from the 'carbonates, in the humid way, but forms a class of 
salts, the osmiates. Osmic acid is expelled by heat from most of its combi- 
nations with bases. A ter 'chloride of osmium has been obtained in combina- 
tion with chloride of ammonium, as a double salt, when osmic acid is saturated 
with that alkali, and treated, after a time, with an excess of hydrochloric acid, 
mercury being also placed in contact with it. After a few days, the liquid 
loses the odour of osmic acid, and when evaporated to dryness leaves the 
double salt, in brown dendritic crystals. The oxide corresponding with this 
chloride, Os0 3 is hypothetic. It cannot be extracted from the above ammo- 
niacal compound, for when an alkali is added to it, ammonia which is set 
free immediately reduces the precipitated oxide to the state of deutoxide. 

Sulphur ets of osmium. — Osmium has a great affinity for sulphur, burning 
in the vapour of that substance, and appears to have as many degrees of sul- 
phuration, as it possesses oxides. 



SECTION IV. 

RHODIUM. 

Eq. 651 A or 52.2; R. 

This metal was discovered, by Wollaston, in the ore of platinum. He found 
the ore from Brazil to contain 0.4 per cent.; native platinum from another 
locality has been found with so much as 3 per cent, of rhodium. 

After the precipitation of the palladium from the solution of native platinum, 
by cyanide of mercury, the solution, in order to obtain the rhodium, may be 
mixed with a little hydrochloric acid, and evaporated to dryness. The cyanide 
of mercury in excess is. decomposed by the hydrochloric acid, and converted 
into chloride of mercury. The dried mass is reduced to a very fine powder, 
and washed with alcohol of density 0.837, which takes up the double chlorides 
of sodium with platinum and iridium, the copper and mercury, but leaves the 
double chloride of rhodium and sodium in the form of a fine deep red powder. 
The rhodium is most easily reduced by gently heating the double chloride in a 
stream of hydrogen gas, and afterwards washing out the chloride of sodium by 
water. 

Rhodium when rendered coherent, is a white metal like platinum, of which 
the density is about 11.* It is brittle and very hard, and may be reduced to 
powder. When pure, it is not dissolved by any acid. But when alloyed with 
certain metals, such as platinum, copper, bismuth or lead, and exposed to aqua 
regia, it dissolves along with those metals. When fused with gold or silver, 
however, it is not dissolved with the other metal. But the most eligible mode 
of rendering rhodium soluble, is to mix it in fine powder with chloride of potas- 
sium or sodium, and to heat the mixture to low redness in a stream of chlorine 
gas. A double chloride is then formed, as with the other platinum metals in 
similar circumstances, which is very soluble in water. The solutions of rhodium 
have a beautiful red colour, the circumstances from which the metal derives its 



* [Rhodium has also been fused by Professor Hare. A mass weighing ninety grains 
was obtained. This metal approximated in colour to the ruddy hue of bismuth, had in its 
perfectly solid state the specific gravity of 11 ; but in congealing exhibited a strong ten- 
dency to crystallize, under which state its specific gravity was 10.8 and a porous condi- 
tion could be discovered by a magnifier. — Proceedings of Am. Phil. Soc. 1842. R. B.] 



SALTS OF BHODIUM, 477 

name (from johv, a rose.) Rhodium may also be rendered soluble in the dry 
way, by fusing it with bisulphate of potash, when the metal is oxidated with 
the escape of sulphurous acid gas. Rhodium is the most oxidable of the pla- 
tinum metals, combining with oxygen when heated to redness in an open vessel, 
and very readily when in fine powder and heated to a cherry-red heat. It 
appears to form two oxides, the rhodous and the rhodic, of which, however, the 
last only has been isolated. 

Oxides of rhodium. — Rhodic oxide, R 2 3 , is produced when the metal is 
ignited with hydrate of potash and a little nitre, in a silver crucible. The metal 
swells up and becomes of a coffee-brown, it is then a compound of rhodic oxide 
and potash, which must be washed with water and afterwards digested in 
hydrochloric acid; the hydrated oxide remains of a gray colour with a shade 
of green and insoluble in acids. The same hydrated oxide, as obtained from 
the double chloride of rhodium and potassium or sodium by precipitation with 
an alkali and evaporation, dissolves slowly in acids, with a certain quantity of 
alkali which is attached to it, assuming a yellow colour and producing double 
salts. The solution in hydrochloric acid is also pale, although it contains chlo- 
ride of potassium, while a solution of the double chloride prepared in the way 
formerly mentioned is a fine red. Hence Berzelius infers that there are two 
isomeric modifications of this oxide, of which the combinations, when in solution, 
are respectively yellow and rose-coloured. The hydrated rhodic oxide contains 
one atom of water, R 2 3 -f HO; two compounds of rhodic oxide with a pro- 
toxide of the same metal or rhodous oxide, appear to exist, R 2 3 -f 3RO and 
R 2 3 -f-2RO. The known compounds of rhodium are not isomorphous with 
compounds of platinum, but this may arise from these two metals affecting 
combination in different proportions, so that their compounds are not analogous 
in composition. Their association and resemblance in other respects afford a 
strong presumption of their being isomorphous bodies. 

Sulphur et of Rhodium. — Rhodium may be united with sulphur by either 
the dry or humid way. The sulphuret of rhodium was used by Wollaston to 
obtain the metal in a coherent mass. 

Chloride, of Rhodium, R 2 C1 3 is obtained from the double chloride of rho- 
dium and potassium, by precipitating the latter metal by fluosilicic acid. The 
dry salt is of a brown-black and not crystalline, it requires a pretty high tem-^ 
perature to decompose it, and then resolves itself at once into chlorine and 
rhodium. This salt deliquesces in air; its solution in water is of a beautiful 
red colour. It appears to exist in combination with a protochloride of rhodium, 
in the rose-red powder obtained by heating rhodium in a stream of chlorine, 
R 2 C1 3 -|-2RC1. The double chloride of rhodium and potassium, prepared by 
the action of chlorine upon a mixture of rhodium and chloride of potassium, 
is 2KCl-f R 2 C1 S +2H0. It retains this water at 212°, but loses it at a higher 
temperature, this salt rarely crystallizes well, but its crystals according to 
Wollaston, are rectangular four-sided prisms, terminated by four-sided pyra- 
mids. The formula of the double chloride of rhodium and sodium is 3Na 
Cl-f R 2 C1 3 + 18H0; it forms large prismatic crystals. Their solution is of a 
beautiful rose colour. 

A sulphate of rhodium is formed when rhodium is ignited with bisulphate 
of potash, it gives a yellow solution. Another sulphate in combination with 
sulphate of potash gradually falls as a white powder, when sulphurous acid is 
added to a solution of the double chloride of these bases. It is nearly insolu- 
ble in water, its formula is KO,S0 3 -fR 2 3 ,3S0 3 . The nitrate of rhodium 
is formed by dissolving the oxide in nitric acid. It forms a deliquescent salt 
of a dark-red colour, R 2 3 4 3NO s ; the last salt combines with nitrate of soda, 
forming dark-red crystals soluble in water but not in alcohol, NaO,NO,+ R„ 
3 ,3N0 5 . 



PART III. 
ORGANIC CHEMISTRY. 



CHAPTER I. 
SECTION I. 

PRELIMINARY OBSERVATIONS. 



By organic substances are meant definite chemical compounds, found ready 
formed in organized beings, and their modifications produced by artificial pro- 
cesses which may be greatly varied. These substances are known to be defi- 
nite in composition when they are crystallizable, or when they enter into com- 
pounds that are crystallizable ; or have, if liquid, a fixed boiling point. In their 
number, which has been vastly increased by late researches, are found many 
acids, several alkaline bodies, and a large class of neutral substances which can- 
not be assimilated to any class of inorganic compounds. Recent inquiries have 
disclosed some unexpected relations between different organic substances, and 
supplied the means of associating groups of them from similarity of composition. 
There is the same evidence of the existence in these substances of compound 
radicals, which may be transferred from a state of combination with one element 
to another, as in the compounds of the inorganic kingdom allowed to contain 
such constituents ; although the organic radicals cannot be isolated and exhibited 
in a separate state, except perhaps in a single instance. The radicals most 
characteristic of organic compounds, hitherto investigated, are of the basyle class, 
bodies resembling therefore the metallic elements in their functions and the 
series of compounds with salt radicals which they are capable of forming. Of 
all these hypothetical radicals ammonium has served as the prototype ; they are 
allowed however to differ in one respect from ammonium and the metals, 
namely in combining readily with hydrogen, which element acts towards them 
as a salt-radical. The supposed prevalence of such radicals in the constitution 
of organic compounds has led M. Liebig to define organic chemistry as the 
chemistry of compound radicals; the whole of which indeed as are of a basyle 
character, including ammonium itself, may be properly assigned to this depart- 
ment of the science. 

Many organic substances are highly complex and contain a large number of 
atoms ; a circumstance which renders them very liable to change, and has led 
to the observation of peculiar modes of decomposition among organio com- 
pounds, indicating novel modes of the action of chemical affinity. 



ORGANIC ANALYSIS. *179 ' 



COMPOSITION OF ORGANIC SUBSTANCES, AND METHOD OF ANALYSIS. 

The elements which usually enter into organic substances are few in number, 
namely carbon, hydrogen, oxygen and nitrogen. Some organic substances 
contain only carbon and hydrogen, as defiant gas and other hydro-carbons; 
more frequently carbon, hydrogen and oxygen, as sugar, gum, many neutral 
bodies, and most organic acids. To these a fourth element is added, nitrogen, 
in the vegeto-alkalies and various other compounds which belong more usually 
to the animal than vegetable division ; indeed carbon prevails in the organic 
world, as silicon does in the mineral, and as most minerals are silicates, so or- 
ganic substances are the compounds of carbon. To these elements certain 
others are occasionally added, although most usually by artificial processes, as 
chlorine in the place of hydrogen, and sulphur, phosphorus, arsenic or tellurium 
in that of oxygen. The elementary analysis of organic matters is determined 
with much exactness, and by means so simple and rapid of execution as to 
render an ultimate analysis often the most read)''test of the purity of a substance. 
The process followed, consists in burning the matter to be analyzed by means 
of oxide of copper, so as to convert its carbon into carbonic acid and its hydro- 
gen into water, which are both collected and weighed ; when the matter con- 
tains nitrogen, the latter is collected in the form of gas. The oxygen, which 
the matter contains, is represented by the excess of its weight over the sum of 
the weights of the carbon, hydrogen and nitrogen found. I shall merely sketch 
the outline of this fundamental and highly important process, referring for the 
minute instructions necessary for its exact execution to Professor Liebig's valu- 
able tract on Organic Analysis.' 15 

The nitrate of copper, decomposed by a red heat in an earthenware crucible, 
gives a fine light oxide, very suitable for the combustion process, and of which 
a considerable quantity must be provided. It is a property of this oxide to be 
reduced with extreme facility at a red heat, by carbon or hydrogen, and at the 
same time to resist an intense temperature, when heated apart from combustible 
matter, without losing a particle of oxygen. The substance to be analyzed, or 
burnt with oxide of copper, we shall suppose to be sugar. 

The tube for combustion is of the most difficultly fusible glass, free from lead ; 
no variety answers better for it than the white Bohemian glass. It is generally 
about 0.4 inch in internal diameter, and 14 or 15 inches long, drawn out, bent 
and sealed at one end, as 

represented (Figure 116,) and Fig. 1 1 6. 

open at the other. To have 
some measure of the quantity 
of oxide of copper to mix with 
the substance to be analyzed, 
the tube is to be filled to three-fourths of its length with pure oxide of copper, 
out of a crucible in which it has just been ignited, and while it is yet warm. 
From 5 to 7 grains of dry loaf sugar in fine powder are first rubbed in a porce- 
lain mortar with a little oxide, with which it is intimately mixed, and by degrees 
the whole oxide of copper is added, which was measured in the tube. Having 
first introduced pure oxide of copper, so as to fill about half an inch at the closed 
end of the tube, the mixture from the mortar is then introduced, followed by a 
portion of oxide employed to rinse out the mortar, and the last covered by pure 
oxide, so as to fill up the tube to within one inch of its open extremity. The 

* Translated by Dr. W. Gregory, and forming Part I of Griffins Scientific Miscellany, 
Tegg, London. 




480 



ORGANIC ANALYSIS. 



lengths occupied by the different layers of pure oxide, mixture, rinsings of mortar 
and again pure oxide are indicated by dotted lines in the figure. The weight 
of the whole oxide of copper used generally exceeds 1200 grains. 

In these operations, the oxide of copper inevitably absorbs a quantity of 
moisture from the air, which may amount to 0.2 or 0.3 grain, and which coming 
off afterwards during the ignition would vitiate the determination of the hydro- 
gen. The tube and oxide must therefore be dried by a heat which will not 

Fig. 117. 





decompose the sugar. This is done by placing the combustion tube C. in a 
wooden trough D, (Fig. 117) and covering it with sand of the temperature of 
250°; connecting it at the same time by a perforated cork, b, with a tube B, 
containing fragments of chloride of calcium, and an exhausting syringe A. By 
means of the latter, air and moisture are Withdrawn from the combustion tube, 
the moisture being retained by the chloride of calcium in B; air is then admitted 
to C by the stopcock a, and withdrawn again by the syringe ten or twelve times. 
The mixture may then be considered dry. 

The furnace for the combustion is made of sheet iron of a trough form (Fig. 

118,) 22 to 24 inches long and 3 inches 
Fig. 118. high. The bottom is 3 inches wide, with 

narrow apertures about half an inch apart, 
which form a sort of grate ; the sides of the 
furnace are inclined outwards, and 4£ inches 
apart at top. To support the combustion 
tube, pieces of strong sheet iron of the form 
D, (Fig. 119,) are rivetted to the bottom of 
the furnace, at intervals ; they are of exactly equal height, with their edges- 
ground flat, and correspond with the round aperture 
in the front of the furnace, A. The furnace rests 
upon two thin bricks supported upon two blocks of 
wood, which are separated a little by a wedge, so as 
to elevate slightly the further end of the furnace as in 
Fig. 120. 




Fig. 119. 



ORGANIC ANALYSIS. 481 

Fig. 120. 




When the heat is to be increased, the furnace is raised a little on one 
side, by a thin bit of tile placed below. Good charcoal, is the fuel employed 
in this furnace; the combustion may be animated by fanning the burning em- 
bers with a square piece of pasteboard; which is safer than raising the fur- 
nace off the bricks. Immediately connected with the combustion tube, by 
means of a perforated cork, is a tube of the form b (Fig. 120,) containing 
fragments of strongly dried, but not fused chloride of calcium. In this tube is 
condensed the water formed in the combustion, of which the weight is ascer- 
tained by weighing the tube, before and after the combustion. Beyond the 
chloride of calcium tube and connected with it by a short caoutchouc tube, 
c, is a glass instrument p m r, containing a strong solution of caustic potash, 
of density 1.25 to 1.27, for the absorption of the carbonic acid produced in 
the combustion. This instrument consists of five balls, of which m is larger 
than the others; no more of the potash ley is put into it than fills the three 
central bulbs, leaving a bubble of air in each. One corner is elevated a little 
by a cork placed under it, and the whole supported upon a folded towel; the 
potash apparatus, when filled with ley, commonly weighs from 750 to 900 
grains. This apparatus is also weighed before and after the combustion, 
and the increase ascertained. 

Before introducing the combustion tube into the furnace, it must be tapped 
smartly in a horizontal position, so as to produce a vacant space 
above the oxide of copper through the whole length of the tube, 
by which the gaseous products may escape (Fig. 116.) The 
same precaution must be taken in the preparatory operation of 
drying the oxide of copper, otherwise it often happens that a por- 
tion of the oxide is thrown forwards out of the tube. Before be- 
ginning the combustion, it is necessary to ascertain that all the 
joinings are tight, by sucking out a bubble or two of air from the ap- 
paratus, by means of the suction tube (Fig. 121,) applied by means 
of a perforated cork not fitting very tightly to the open end of the 
potash apparatus. The slight exhaustion causes the ley to stand \h or 2 
inches higher in the inner limb m of the potash apparatus than in the outer 
limb. This elevation will be maintained if no air enters by the cork or 
caoutchouc joint, and the apparatus is then certainly tight, but not so if the 
level changes and the liquid falls back into the middle part of the apparatus. 

In conducting the combustion, the anterior portion of the tube, containing 
only oxide of copper, is first surrounded by red hot charcoal. Thep IG# j22. 
fragments of charcoal are kept in their place and the heat pre- 
vented from spreading, by a screen, (Fig. 122,) of sheet iron, of 
the same width as the furnace. This screen is slowly moved back- 
wards, by half an inch to an inch at a time, and the fire space im- 
mediately filled up with red hot charcoal, so as to raise rapidly the 
portion of tube newly exposed to a red heat. A screen (Fig. 123) should be 
placed upon the front of the furnace, to prevent the cork being burned and 
41 




482 



PRELIMINARY OBSERVATIONS. 




the chloride of calcium tube being heated, by radiation from the furnace, 
But the fore end of the tube, which is empty and projects an 
inch beyond the furnace, should be kept so hot during the whole 
operation that no water condenses in it; in the course of twenty 

Iljj IB minutes or half an hour the screen has been moved to the end 
xjJI^P' of the tube, and the combustion completed. When the evolu- 
tion of gas stops all at once, the combustion is certainly com- 
plete, and a good result is obtained; the tube should be heated red hot, but not 
to bright redness; it begins to stick to the supports when heated too hot. 

As soon as the evolution of gas terminates, the potash ley begins to rise 
into the bulb m. The pointed extremity of the combustion tube should then 
be broken by means of a pair of pliers, after removing the charcoal from that 
end of the furnace. An open tube A, 12 or 15 inches long, is then placed 
over the opened end, and supported by a stand, (Fig. 124,) while by means of 



Fig. 124. 




=^ 



the suction tube B, a certain quantity of air is drawn by the mouth through 
the potash apparatus. The whole watery vapour and carbonic acid remaining 
in the combustion tube, are thus brought into the chloride of calcium tube and 
potash apparatus, and completely absorbed. 

The data furnished by the combustion afToid the means of calculating the 
composition of the substance analyzed, as the composition of water and car- 
bonic acid is known, the former consisting of 1 hydrogen and 8 oxygen in 9 
parts, and the latter of 27.675 carbon and 72.325 oxygen in 100 parts: 

The hydrogen is one ninth of the increase of weight in the chloride of cal- 
cium tube. 

The carbon is 27.67 per cent, of the increase of weight in the potash bulbs. 

The oxygen is the quantity obtained by adding the weights of the hydro- 
gen and carbon together, and deducting their sum from the weight of matter 
originally employed. 

The following are the details of a particular analysis of sugar (Dumas.) 



Weight of Sugar. 


, . 


. 600 


Weight of Carbonic Acid. 


. . 


. 921 


Weight of Water. 


. 


. 353 


These give by calculation: — 






Carbon. 


254.6 . 


42.4 


Hydrogen 


39.2 . 


6.5 


Oxygen. . . . 


306.2 . 


51.1 



600 



100 



ORGANIC ANALYSIS. 483 

The atomic constitution of sugar is obtained from these results, by dividing 
the quantities of carbon, hydrogen and oxygen in the last column, by their 
equivalents, 76, 12. p and 100. We thus obtain 0.558 of an equivalent of car- 
bon, 0.520 of an equivalent of hydrogen and 0.511 of an equivalent of oxy- 
gen, which are more nearly proportional to the following than any other whole 
numbers, 12 carbon, 11 hydrogen, 11 oxygen; and give C 12 H 11 11 , the 
usually received formula for cane sugar. 

The estimation of nitrogen, when present in an organic substance, requires 
another combustion in which that gas is determined by measurement. This 
gas generally escapes in a free state, mixed with the carbonic acid and watery 
vapour; but frequently deutoxide of nitrogen is formed, which renders the de- 
termination of the nitrogen difficult; to decompose the latter it is necessary to 
have a portion of copper turnings in the anterior part of the tube, which are 
kept at a full red heat during the combustion, as from the screen m (Fig. 125) 
to the mouth of the tube. This is followed by a layer of pure oxide from m 
to B, and then the mixture from B to A; as soon as the copper and oxide are 

Fig. 125. 




at a red heat, the tube is heated from the closed end, a second screen n being 
gradually advanced from that extremity. When the proportion of nitrogen is 
not inconsiderable, it is generally sufficient to determine its relation by volume 
to the carbonic acid evolved at the same time. This is done by attaching a 
bent quill tube (Fig. 125) to the mouth of the combustion tube, by which the 
gas evolved is conveyed to the mercurial trough, and collected at different 
stages of the combustion in a small graduated jar. By passing up a [e\v 
drops of caustic potash into the gas in the jar, the carbonic acid is absorbed 
and the nitrogen remains. If the proportion between the volumes of the two 
gases thus observed is the same in several successive trials, and no red nitrous 
fumes be perceived on mixing the gas with air, this result is sufficient for the 
nitrogen. The whole quantity of carbonic acid produced in the combustion 
being known from a previous analysis conducted in the usual way, we can 
obtain the volume of nitrogen by calculation, and thence its weight. Or, as 
two volumes of carbonic acid and of nitrogen represent both one atom of carbon 
and nitrogen, the atoms of these two gases are in the same number as the vo- 
lumes observed; consequently when the weight of the carbonic acid is known, 
that of the nitrogen may be calculated from the atomic weights of carbonic 
acid and nitrogen. 

For the analysis of uric acid, in which the volumes of the nitrogen and car- 
bonic collected are as 4 to 10, and of bitartrate of ammonia in which they are 
as 1 to 8, this method answers very well, but when the proportion of nitrogen 
is smaller than the last, or when the nitrogen appears in a variable proportion 
at different stages of the analysis, then it is necessary to collect and measure 
the whole nitrogen evolved, which is not easily done with accuracy. To get 
rid of the nitrogen of the air contained in the tube, a combustion tube is chosen 
24 inches long, 6 inches of which at the closed end are filled with carbonate of 
copper, then follow 2 inches of pure oxide of copper, next the mixture of the 



484 PRELIMINARY OBSERVATIONS. 

substance with oxide of copper, then another layer of pure oxide, and lastly a 
layer of copper turnings. The air is exhausted from the tube by a syringe, and 
the tube filled with carbonic acid by heating one half of tjie carbonate of cop- 
per ; the exhaustion and evolution of carbonic acid are several times repeated, 
till the whole air is certainly withdrawn from the tube, and the latter is filled 
with carbonic acid. The combustion of the mixture is then conducted as in the 
previous case, the gases however are received in a large graduated jar, over 
mercury, half full of a strong solution of caustic potash. After the combustion 
is completed, heat is again applied to the end of the tube containing the remaining 
half of the carbonate of copper, and carbonic acid evolved which sweeps out the 
last portions of nitrogen into the receiver, where the volume of that gas is 
observed. 

MM. Will and Varrentrapp have lately proposed the following excellent 
method of determining the nitrogen in organic substances, which is likely to 
supersede every other. The substance is mingled with a mixture of caustic 
lime and hydrate of soda, and heated to redness in a combustion tube* All the 
nitrogen of the substance escapes as pure ammonia, which may be condensed 
in a small apparatus containing dilute hydrochloric acid. This liquid is after- 
wards mixed with chloride of platinum, and brought to dryness in a water-bath ; 
the double chloride of platinum and ammonium remaining is washed with a 
mixture of alcohol and ether, in which it is perfectly insoluble. The quantity 
of nitrogen is calculated from the weight of the chloride of platinum and ammo- 
nium, or from the metallic platinum which it leaves behind when heated to 
redness. 

Oxide of copper is not applicable for the combustion of substances containing 
chlorine, owing to the volatility of the chloride of copper, a portion of which 
passes into the chloride of calcium tube, and vitiates the determination of the 
hydrogen. Chromate of lead is then employed in the combustion tube, with 
the same manipulations as with oxide of copper. This salt must first be strongly 
ignited till it begins to melt and then be reduced to a very fine powder ; the 
chloride of lead is perfectly fixed at a low red heat. The chromate of lead is not in 
the slightest degree hygroscopic, and is likely to be preferred to oxide of copper, 
where it is desirable to determine the proportion of hydrogen with extreme 
accuracy. 

Notwithstanding the great value of the analytical results of this method, and 
the agreement almost perfect in repetitions of the same analysis, there can be 
little doubt that the method itself is not absolutely exact. From the rigorous 
examination to which the combustion process has lately been submitted by M. 
Dumas, it appears to give less than the true quantity of carbon. The loss of 
carbon is ascribed to several causes : some is deposited here and there in the 
tubes and for want of oxygen not burned ; the reduced copper is partly con- 
verted into carburet of copper ; the liquid potash allows a portion of the carbonic 
acid to escape, and lastly the air which is drawn through the apparatus takes 
up some water from the same potash and diminishes its weight. This loss of 
carbon was hitherto concealed by carbonic acid being allowed to contain more 
carbon than it really has, so that the carbon lost in the process was made up in 
the calculation ; and the formulas deduced from analyses are only true from the 
accidental compensation of these two errors. Dumas reduces the proportion 
of carbon in carbonic acid from 27.67 to 27.27 per cent., and obtains for the. 
atom of that element the number 75, instead of 76.4. This important result he 
has deduced by collecting and weighing the carbonic acid produced by the 
combustion of a known weight of pure charcoal, in the forms of graphite and 

* [One part of hydrate of soda and two of quicklime form a suitable mixture. Journ. 
de Pharm. and de Qhim. and Am. Journ. of P harm., July, 1842.] 



MODIFICATIONS OF ORGANIC COMPOUNDS. 485 

the diamond.* Drs. Marchand and Erdman of Berlin have repeated these 
analyses with the same results ; it is now indeed generally allowed that the 
atomic weight of carbon of Berzelius is too high, bat chemists are not yet agreed 
as to the amount of reduction to be made. MM. Redtenbacher and Liebig 
conclude that the atomic weight of carbon is the intermediate number 75.854, 
from an elaborate series of experiments undertaken to determine the point, in 
which the proportion of silver in the acetate, malate, racemate and tartrate of 
that base was ascertained with great accuracy; the atomic weight of silver, 
respecting which there is little uncertainty, being taken at 1351.6. It has also 
been shown by Dr. Clark that when certain corrections are made on the calcu- 
lations of' Berzelius' experiments, they really give a number for carbon nearly 
approaching to this. 

To give the process of organic analysis all the precision of which it is sus- 
ceptible, M. Dumas requires attention to the following circumstances. 1. To 
triple at least the quantity of matter usually employed. 2. After the ignition of 
the combustion tube to pass through it a large quantity of oxygen, so as to burn 
the deposited carbon and re-oxidate all the copper, which gets rid of the carburet 
of copper. 3. For the reception of the water to employ a chloride of calcium 
tube accompanied by a tube filled with fragments of pumice impregnated with 
oil of vitriol. 4. To absorb the carbonic acid, Liebig's bulb apparatus containing 
solution of potash is to be used, accompanied by tubes containing potash moist- 
ened with the potash ley on one side, and dry potash on the other ; the dry 
potash arrests the water with which the gas has become charged by passing 
through the liquid in the bulbs.f The most important observation of Dumas is 
that the combustion of the carbon is never complete, unless oxygen be passed 
through the tube containing the mixture of oxide of copper and matter to be 
analyzed, and the matter be thus burned in an atmosphere of oxygen. This is 
the principle of the method of organic analysis originally practised by Dr. Prout, 
by which he was led to the conclusion that the atom of carbon is exactly 6 on 
the hydrogen scale, or 75 on the oxygen scale.! M. Dumas, who now adopts 
this conclusion, has therefore been conducted to it by a recurrence to Dr. Prout's 
own mode of investigation. 



MODIFICATIONS OF ORGANIC COMPOUNDS PRODUCED BY ARTIFICIAL 

PROCESSES. 

It is generally stated that no substances properly organic can be produced 
by directly uniting their ultimate elements ; although a few organic compounds 
may be formed from substances less complex than themselves, but which are 
not elementary; as urea from cyanic acid and ammonia, the acid named, in 
common with cyanogen itself and all its compounds, being considered organic, 
because usually derived from the decomposition of azotized matters. But it 
has unequivocally been proved that nitrogen gas unites with charcoal under 
the influence of carbonate of potash at a red heat, and forms cyanide of potas- 
sium (L. Thompson, Fownes.)§ The last salt also yields ammonia when 
decomposed by water; so that cyanogen, and through cyanogen ammonia, can 
be primarily derived from their elements contained in the organic world. The 
usual course however pursued by the chemist in this department is to form new 

* MM. Dumas and Stasa, Annales de Chimie et de Physique, 3me Serie, tome 1, p. 5. 
(1841.) 

t Annales de Chimie et de Physique, 3me Serie, tome 1, p. 39, where the improved 
process is minutely described and the apparatus figured. 

t Phil. Trans. 1827; or Brande's Manual of Chemistry, p. 1060. 

§ Originally observed by Desfosses ; Journal de Pharmaeie, t. 14, p. 280 (1828.) 

41* 



486 DISTILLATION WITH AN ALKALI. 

compounds by the alteration of compounds supplied to him by nature. These 
changes he affects by various agencies, such as hydrate of potash, distillation 
by heat, acids, oxygen, chlorine, &c. The most uniform and definite of these 
actions are those of a hydrated alkali and dry distillation. 

Distillation with an alkali. — When an organic substance containing no 
nitrogen is fused with a sufficient quantity of hydrate of potash, no charcoal 
is liberated. The products formed are those which result from oxidation; 
water is generally decomposed, of which the oxygen enters into combination 
with the hydrogen and carbon of the organic matter, while the hydrogen is 
disengaged as gas. Thus when acetate of soda is decomposed by hydrate of 
barytes, the hydrogen of the latter is liberated. M. Dumas has shown that 
alcohol and other bodies of the same character, distilled at a moderate heat 
with a mixture of hydrate of potash and quicklime, each gives rise to a pe- 
culiar acid, which remains in combination with the potash, by losing 2 eq. of 
hydrogen (disengaged as gas,) and acquiring 2 eq. of oxygen; alcohol to acetic 
acid, wood spirit to formic acid, fousel oil to valerianic acid, ethal to ethalic 
acid; and that this mode of decomposition is characteristic of alcohols. Gly- 
cerine, which in some respects resembles an alcohol, when treated in the 
same way, but at a very low temperature, does not give a peculiar glyce- 
ric acid, but resolves itself into acetic and formic acids, with the loss of 
two equivalents of hydrogen and assumption of two of oxygen. Acetone 
transmitted in the state of vapour over the mixture of hydrate of potash and 
lime heated to redness, gives nothing but carbonic acid, which remains in 
combination with the alkali, and light carburetted hydrogen C 2 H 4 . The 
vapour of aldehyde passed over the same mixture at a lower temperature gives 
acetate of potash and free hydrogen, losing only one equivalent of hydrogen 
and acquiring one of oxygen, or the reaction is similar to what occurs with 
the next substance to be mentioned, to which aldehyde has considerable ana- 
logy.* Oil of bitter almonds distilled with dry hydrate of potash, gives 
hydrogen gas and benzoate of potash. 

According to the temperature, ulmic, acetic and oxalic acids appear in 
other cases, or carbonic acid only. Thus tartaric acid fused with hydrate of 
potash gives the acetate and oxalate of potash. Acetate of potash distilled 
with a mixture of hydrates of potash and lime, gives carbonate of potash and 
light carburetted hydrogen gas, which on that account is also named the gas 
of the acetates. Formic acid, alcohol, and bodies in general consisting of 
carbon, oxygen and hydrogen, when distilled with anhydrous barytes, give 
the same gas. When substances containing nitrogen are boiled in a solution 
of eaustic potash, or fused with the dry hydrate, ammonia is evolved, and 
acids containing no nitrogen remain in combination with the potash. Some 
bodies containing much nitrogen lose only, with, dry hydrate of potash, a 
portion of their nitrogen in the form of ammonia; and the rest acquiring oxy- 
gen, assumes the form of eyanic acid, and is protected by the potash from 
farther decomposition. 

When the acetate of any metallic oxide capable of retaining carbonic acid 
at a red heat, such as the aeetate of soda, potash, barytes, &c, is distilled, a 
carbonate remains in the retort, while a combustible liquid, acetone C 3 H 3 
distils over. M. Fremy has shown that sugar, starch and all those ternary 
compounds of carbon, hydrogen and oxygen, in which the last two are in the 
proportion to form water, are decomposed when heated in contact with lime 
in the same manner as acetic acid. They afford acetone, with water and car- 
bonic acid. Benzoic acid distilled with three times its weight of hydrate of 
lime forms carbonate of lime, with a volatile liquid C l2 H 6 , the benzin of 

* Annales de Chimie et de Physique, tome 73, p. 113. 



DRY DISTILLATION. 487 

Mitscherlich and bicarburet of hydrogen of Faraday. The neutral benzoate of 
lime gives with other products the liquid benzone, C 13 H 5 0. Distilled from 
lime stearic, margaric and oleic acids lose the elements of carbonic acid, and 
form neutral volatile products, stearone, margarone and oleone. The names 
of such pyrogen bodies terminate in one as contain one atom of oxygen and 
are neutral. Margarone carried in its turn over lime at a red heat, loses its 
oxygen, in the form of carbonic acid, and paraffin is produced, which is a 
binary compound of carbon and hydrogen. Thus the alkali determines 
throughout the formation of a highly oxidized acid body, with which it unites 
and, the other products are consequently partially or completely deoxidized. 

Dry distillation. — Many organic substances are volatile and may be distilled 
at a moderate heat without alteration, such as alcohol and most essential oils; 
but a larger number are fixed. The latter when submitted alone to distillation 
usually abandon carbon, and form new and more simple volatile products. 
Three periods are distinguished by Liebig in the dry distillation of the fixed 
organic acids, from the different compounds formed according to the tempera- 
ture. In the first organic acids of less atomic weight are produced, with carbonic 
acid, water and inflammable liquids soluble in water. The bibasic and tribasic 
organic acids, by losing the elements of water and carbonic acid, are converted 
into theirvolatile pyr-acids, which are less basic, generally mono-basic; thus 
tartaric acid CgH^O, is converted into pyro-tartaric acid 0,H 3 O 3 , by losing 
three atoms of carbonic acid C 3 6 and one atom of water HO; but these pyr- 
acids can rarely be distilled again by themselves, without partial decomposition. 
In the second period of the distillation, bodies are obtained which result from 
the destruction of the preceding compounds; thus the oxygen of the acids, 
uniting with the carbon and hydrogen of the combustible bodies, gives rise to 
more simple bodies, such as carbonic oxide, carbonic acid and water; some 
charcoal is generally set at liberty, while another portion of it enters into 
combination with the excess of hydrogen, and produces liquid or solid volatile 
hydrocarbons. In the last period, nothing is obtained but charcoal and a 
gaseous mixture, principally composed of carbonic acid, carbonic oxide, olefiant 
gas and light carburetted hydrogen. Substances containing nitrogen, give am- 
monia in the first period, and cyanogen or hydrocyanic acid in the last. 

The decomposition of citric acid by heat, has been more minutely investi- 
gated than any other, by M. Crasso, and is particularly interesting from the 
variety of products it affords, at different stages of the decomposition. After 
losing its water of crystallization, the citric acid, C ] . 2 H 5 11 , first undergoes 
a decomposition, of which the products are a new and fixed acid, aconitic acid, 
C 4 H 2 4 , also found in nature being the acid of the aconitum napellus, 
together with one atom of acetone CgH^O, four atoms of carbonic oxide 
C 4 4 , and one atom of carbonic acid C0 2 . By a continuance of the heat, 
the fixed aconitic acid itself is decomposed, three atoms of it C 12 H 6 12 » af- 
fording two atoms of a volatile pyr-acid, named itaconic acid (2C 5 H 3 4 ,) and 
two atoms of carbonic acid C 2 4 . The itaconic acid again is decomposed 
when heated to its point of ebullition, and gives a more volatile and stable acid, 
named citraconic acid C 5 H 3 4 , which is consequently isomeric with the pre- 
ceding acid. It is believed, however, by Crasso, that the last is the only mo- 
no-basic acid in the series, and that the true formulae of the hydrates of the 
three new acids produced by the decomposition of citric acid by heat, are, 
with that of the original acid itself: 

Citric acid. .... C, o H i n + 3HO 
Aconitic acid. . . ... . C^HgO^-f- 3HO 

Itaconic acid C 10 H 6 O 8 ~-f2HO 

Citraconic acid. . . . C 5 H 3 4 -f HO* 

* Annates de Chimie et de Physique, 3me Serie, tome 1, p. 311. 



488 PRELIMINARY OBSERVATIONS. 

By the united action of heat and bases, other transformations of acids have 
been effected. Thus malic acid is converted into fumaric and equisetic acids, 
and citric acid into aconitic and tartaric acids, when their compounds with ox- 
ide of antimony or potash are heated so long as water is disengaged. 



ACTION OF OXYGEN— EREMACAUSIS. 

Organic compounds when dry and in a state of purity are generally capable 
of resisting the action of the air or of free oxygen, at the usual temperature; but 
a considerable number are affected by that element; the various essential and 
fixed oils absorb oxygen in different degrees, the first becoming resins and 
the second acquiring the drying properties of varnishes; the essential oil of 
bitter almonds is gradually converted into benzoic acid, and the vapour of 
ether passes slowly into acetic acid, while white indigo and other colouring 
principles undergo remarkable changes from a rapid absorption of oxygen. 
The direct oxidation of alcohol and ether, which gives rise to acetic acid, is 
greatly favoured by the contact of spongy platinum. The highly oxygenized 
acids act with much more energy upon organic compounds and give rise to 
various products according to the quantity of oxygen communicated. Thus 
alcohol is converted by oxidating matters, into acetal, aldehyde, acetic acid, 
formic acid, oxalic acid, carbonic acid and water. In these reactions, the 
oxygen is frequently observed to affect the hydrogen exclusively, which is 
converted into water, while a quantity of oxygen exactly equivalent to the 
hydrogen thus withdrawn, enters into combination with the remaining ele- 
ments, and appears to be substituted for the hydrogen. Thus by the action 
of four atoms of oxygen, upon one atom of alcohol C 4 H 5 O-f-H0, two atoms 
of hydrogen are withdrawn as water, while two atoms of oxygen are at the 
same time absorbed by the remaining elements of the alcohol, which becomes 
hydrated acetic acid C 4 H 3 3 4-HO. When anhydrous sugar C, 2 H g 9 is 
treated with hypermanganate of potash, the nine atoms of hydrogen which 
the former contains are replaced by nine atoms of oxygen, and six atoms of 
oxalic acid formed 6C 3 ;i . 

The presence of water greatly promotes the action of the oxygen of the 
atmosphere upon organic substances. The name eremacausis has been ap- 
plied by Liebig to the slow combustion or oxidation of organic matters in air. 
Vegetable juices evaporated by a gentle heat in air allow a brown or brownish- 
black substance to precipitate, known as extractive matter, and similar in 
properties from whatever juice it is formed. It is insoluble or very sparingly 
soluble in water, but dissolved with facility by alkalies. By the action of air 
upon solid animal or vegetable matters, a similar pulverulent brown substance 
is formed known as humus. According to an observation of De Saussure, the 
sawdust of oak wood converts oxygen into carbonic acid, without any change 
of the volume of the gas; but while dry sawdust lost three parts by weight of 
carbon in this way, it diminished in weight by fifteen parts altogether, show- 
ing that twelve parts of water were at the same time separated from the wood. 
Hence the proportion of carbon in decaying wood increases with the progress of 
its decay; and it is concluded that the hydrogen only is oxidized at the expense 
of the oxvgen of the air, while the carbonic acid is formed from the elements 
of the wood (Liebig.) The composition of pure woody fibre or lignin being 
C 36 H 22 22 , two different specimens of mouldered oak wood, (the humus 
from oak wood) were found to be C 35 H 2 ? 2 and C 34 H, i O l 8 , or for every 
two atoms of hydrogen oxidized by the air, one atom of carbonic acid (C0 2 ) 
has been formed at the same time from the elements of the wood and set free. 
When water is present and the access of air restrained, the decomposition of 



EREMACAUSIS. 489 

wood appears to proceed in a different manner; for while carbonic acid ia 
generated as before, a certain quantity of water enters into chemical combina- 
tion, white mouldering beechwood being found to have a composition cor- 
responding with the formula C 33 H 2 _0 24 . There is reason, however, to 
suppose the interference in such cases of mouldering, of a species of fermen- 
tation such as was observed when rags were placed in heaps and wetted in the 
preparation of a substance for the fabrication of paper, according to the old 
process in use before the application of chlorine. The rags became warm and 
disengaged a gas, while their weight diminished from 18 to 25 per cent. It 
is probable that in this, as well as other putrefactive processes, the oxygen of 
the water assists in the formation of carbonic acid. 

Wood coal or brown coal, which retains the structure of the wood un- 
changed, appears to be produced by a similar process of decomposition. A 
specimen free from bituminous matter was found to have a composition ex- 
pressed by the formula C 33 H 21 16 ; and may therefore have been produced 
from woody fibre by the separation of one equivalent of hydrogen and three 
equivalents of carbonic acid. In all varieties of wood coal, the proportion of 
oxygen in relation to the hydrogen is diminished, these elements existing in 
the original woody fibre in the same proportion as in water, indicating a dis- 
engagement of carbonic acid from their substance, which appears still to go 
on at great depths in all the strata of wood coal. The composition of the 
splint coal of Newcastle and cannel coal of Lancashire being C 24 H 13 0, ac- 
cording to the analyses of both Richardson and Regnault, mineral coal is 
obviously formed from woody fibre in a different manner from brown coal. 
The composition of splint and cannel coal is obtained by the subtraction of 3 
atoms of carburetted hydrogen, 3 atoms of water, and 9 atoms of carbonic 
acid from the formula of wood (Liebig:) 



Three atoms of carburetted hydrogen. C 3 H C 
Three atoms of water. . . H 3 3 
Nine atoms of carbonic acid. . C„0. „ 



Mineral coal. 



C 36 H 22 22 ==wood. 

C 12 H 9°21 



C 24 H 13 



Caking coal from Caresfield, near Newcastle, is C 20 H 9 O, or contains the 
elements of cannel coal, minus the constituents of olefiant gas C 4 H 4 (Liebig.) 
The inflammable gas of coal mines is principally light carburetted hydrogen, 
but it has been observed by Bischoff occasionally accompanied by notable 
quantities of s olefiant gas. Such decompositions, however, are not due to 
eremacausis, and indeed take place in materials covered by such a mass of 
strata as must entirely exclude air, but are more analogous to the internal re- 
actions observed in organic matters, and known as species of fermentation, in 
which the elements of a compound substance (such as sugar) divide themselves 
into two or more groups, without the incorporation of any extraneous element, 
except perhaps the constituents of water. 

The absorption of oxygen by alcohol in its acetification is a true eremacausis, 
so also is the process of nitrification. Oxidation is promoted in many organic 
bodies by contact with an alkali ; thus alcohol holding potash in solution soon 
becomes brown from oxidation, and a resinous matter appears with all the pro- 
ducts of the decomposition of aldehyde. The oxidation of gallic acid, hematin 
and many other compounds is promoted by the same influence ; many vegetable 
substances exhibit a rapid absorption of oxygen on the addition to them of 
ammonia, and form splendid violet or red coloured liquids, such as the colour- 
ing principles of the lichens. On the other hand, eremacausis seems to be en- 



490 PRELIMINARY OBSERVATIONS. 

tirely prevented when water is excluded, or when the substance is exposed to 
a temperature of 32°. The processes of fermentation and putrefaction, which 
are different from eremacausis, appear to be necessarily preceded by an ab- 
sorption of oxygen. Thus the juice of grapes pressed under mercury and col- 
lected in a jar filled with that metal was observed by Gay-Lussac to keep with- 
out change, but on admitting a bubble of air to the liquid, the vinous fermenta- 
tion immediately commenced. The perfect exclusion of air is also the basis of 
the valuable process for preserving animal and vegetable food, without the use 
of antiseptics, first introduced by Appert. The materials are usually placed in 
canisters with a quantity of fluid, which is kept in a state of ebullition for some 
time, and the openings hermetically closed with solder while the vessels are 
entirely filled with steam. Eremacausis is also prevented or much retarded by 
aromatic substances, empyreumatic substances and oil of turpentine, the va- 
pours of which retard the oxidation of phosphorus and of phosphuretted hydro- 
gen in a similar manner. It is also arrested by mineral acids and salts of mer- 
cury, which appear to act by combining with the organic matter ; alcohol, a 
strong solution of sugar, common salt and many other saline substances are 
supposed to owe their antiseptic properties in a great measure to their affinity 
for water, which reduces animal or vegetable matters in contact with them to a 
state of dryness in which they are little liable to decomposition. Thus a piece 
of dry butcher-meat covered with dry salt is found after twenty-four hours 
swimming in brine, the salt attracting water from the meat, and leaving it not 
humid enough for chemical action. 



ACTION OF CHLORINE, ITS SUBSTITUTION FOR HYDROGEN, 
CHEMICAL TYPES. 

M. Gay-Lussac observed, several years ago, that bees r wax exposed to chlo- 
rine gas absorbed the latter, giving rise to a disengagement of hydrochloric acid, 
without any change of volume in the gas from the operation. The reason is 
that the wax loses a volume of hydrogen equal to the volume of chlorine which 
it absorbs, the constituents of hydrochloric acid gas being united, it is to be 
remembered, without any condensation of volume. M. Dumas afterwards re- 
peated the experiment with oil of turpentine, and obtained a similar result ; 4H 
in the latter body being replaced by 4C1, or C 20 H 16 becoming C 20 H 12 C1 4 . 
The action of chlorine on a great number of organic substances has since been 
observed by MM. Dumas, Laurent, Regnault, Malaguti and Others, and found 
to be remarkably uniform. The investigation has led to the formation of a large 
number of new compounds, and to the propagation of certain theoretical views 
by M. Dumas, which have had an extraordinary influence on the recent progress 
of organic chemistry. 

When light carburetted hydrogen gas C 2 H 4 , is allowed to mix gradually 
with three times its volume of chlorine, in strong sunshine, the whole 4 eq. of 
hydrogen are converted into hydrochloric acid, which is liberated, while the 2 
eq. of carbon combine with 4 eq. of chlorine, and form a peculiar liquid chloride 
of carbon C 2 C1 4 ; so that the hydrogen of the former compound appears to be 
simply replaced by chlorine in the latter.* The removal of the whole hydrogen 
by chlorine takes place at once, in this hydrocarburet without the formation of 
any other intermediate product except a trace of chloroform, but in other cases, 
where there are several equivalents of hydrogen, the latter are often removed 
and replaced by chlorine one by one, and a series of bodies formed in which 
while the hydrogen diminishes, the chlorine increases in an equal proportion ; 

* Dumas, An. de Ch. et de Ph. t. 73, p. 94. 



SUBSTITUTION OF CHLORINE FOR HYDROGEN. 491 

such are the compounds produced by the action of chlorine on Dutch liquid 
already described (page 270,) and the remarkable series produced by the re- 
peated action of chlorine upon hydrochloric ether.* The two series referred to, 
exhibit a remarkable isomerism, the corresponding products having the same 
composition although distinguishable by their physical properties and by the 
effect of re-agents upon them. These chlorine compounds are all volatile 
liquids, with the exception of the solid perchloride of carbon which is common 
to both series. 



OLEFIANT GAS AND BODIES DERIVED FROM IT BY THE ACTION OF CHLORINE. 



defiant gas 

First product, Dutch liquid 

Second product 

Third product . 

Last product, perchloride of carbon 



C 4 H 3 +H 
C 4 H 3 C1 +HC1 
C 4 H 2 C1 2 +HC1 
C 4 H Cl 3 +HCi 

c 4 ci 6 



HYDROCHLORIC ETHER (CHLORIDE OF ETHYL) AND BODIES DERIVED FROM IT BY THE 
ACTION OF CHLORINE. 

Hydrochloric ether C 4 H 5 C1 

Monochlorinated ditto C 4 H 4 C1 2 

Bichlorinated ditto C 4 H,C1 3 

Trichlorinated ditto C 4 H 2 C1 4 

Quadrichlorinated ditto C 4 H CL 

Perchloride of carbon C 4 C1 6 

It appears from the second table that hydrochloric ether is affected at once 
by two atoms of chlorine, one of which seizes an atom of hydrogen and removes 
it in the form of hydrochloric acid, while the second atom of chlorine enters in- 
to the compound remaining, which Regnault distinguishes as monochlorinated 
hydrochloric ether, the name having reference to the mode of derivation of the 
compound and not its composition.! The latter body when exposed to chlorine 
is likewise affected by two atoms, one of which siezes and withdraws an atom 
of hydrogen, while the other unites with the remaining elements, forming bichlo- 
rinated hydrochloric ether. The trichlorinated and quadrichlorinated com- 
pounds, and the perchloride of carbon, which follow, have the same mode of 
formation ; and as one atom of chlorine is communicated for each atom of hydro- 
gen withdrawn, the entire number of constituent atoms remains the same, or 
ten, throughout the series, and the last member differs only from the first, in 
having 5 atoms of chlorine instead of 5 of hydrogen. To exhibit the compli- 
mentary function of the chlorine and hydrogen in these bodies, their formulae 
may be written thus : 

C 4 H 5 C1. C 4 **«C1. C 4( ^CL e 4 ***ci. c 4 ** CI. C 4 C1 5 C1. 

Chloromethylic ether or chloride of methyl C 2 H 3 C1, a body having the same 
relation to wood-spirit that hydrochloric ether has to alcohol, gives rise to an 
analogous series of chlorinated compounds when a stream of chlorine is passed 

* Regnault, An. de Ch. et de Ph. t. 71, p. 353. 

t " Chlorinated " appears to be a preferable term to chloruretted, to apply to such a com- 
pound, as the last is already used in a different sense. 



492 PRELIMINARY OBSERVATIONS. 

through it, the product being treated in its turn with the gas, and the same 
process repeated with the new product ; when the hydrogen is then entirely- 
withdrawn, and a chloride of carbon remains, the same that is derived from light 
carburetted hydrogen (Regnault.) The bodies of this series are : — 

C 2 H 3 C1. C^Cl. C 2 ^j CI. C 2 C1 3 CL 

All these chlorinated compounds possess the neutral character of the bodies 
from which they are derived. Malaguti has also observed that ether (oxide of 
ethyl) may lose two equivalents of hydrogen and gain two of chlorine, C 4 H 5 
becoming C 4 H 3 C1 2 0, without any of its essential properties undergoing altera- 
tion ; for its power of combination remains the same, and chlorinated ether is 
still ether. Oxalic ether or the oxalate of oxide of ethyl, may have its whole 
five atoms of hydrogen replaced by five atoms of chlorine* and chlorinated 
oxalic ether, or chloroxalic ether is formed; C 4 H 5 0+C 2 3 becomes C 4 Cl 5 0-f 
C 2 3 , or adopting empirical formulae, C 6 H 5 4 becomes C 6 C1 5 4 . Now each 
of these ethers is the base of a class of salts, the oxalovinates and chloroxalovi- 
nates ; each of them, also, is affected by dry ammoniacal gas, and by solution 
of ammonia in the same way, forming oxamethane or chloroxamethane with 
the first re-agent, and oxamide with the second.* 

OXALIC ETHER, AND COMPOUNDS DERIVED FROM IT. 



Oxalic ether 


. , 


C 6 H 5 


4 




Oxalovinic acid (hydrated) 


C 6 H, 


4 +C 2 3 


,H0 


Oxamethane 


. 


C 6 H 5 


4 -fC 2 o ,NH 2 


Oxamide . 




c 2 o 2 


,NH 




CHLOROXALIC ETHER, 


AND COMPOUNDS DERIVED FROM 


IT. 


Chloroxalic ether 


, , 


C 6 C1 


s0 4 




Chloroxalovinic acid 


(hydrated) 


C 6 C1 


5 4 + C 2 : 


,HO 


Chloroxamethane 


. 


C 6 C1 


A+c 2 o 2 


,NH 2 


Oxamide . 


• 


c 2 o 2 


,NH„ 





It rarely happens that the crystalline forms of corresponding hydrogen and 
chlorine compounds can be compared, for most frequently the two substances, 
or at least one of them, does not crystallize, and is altogether incapable of 
exact measurement. But M. de la Provostaye has succeeded in instituting a 
comparison between the crystalline forms of oxamethane and chloroxamethane* 
which he finds to be isomorphous, or rather different secondary forms derived 
from the same fundamental form.t This would establish the isomorphism of 
chlorine and hydrogen, but it is to be regretted that so important a conclusion 
should rest upon a single instance, and one also in which, as Mitscherlich 
remarks, the usual complete identity of form of isomorphous bodies is not 
observed. 

By exposing pure acetic acid to the action of dry gaseous chlorine, under 
the direct influence of the solar rays, M. Dumas has replaced the whole hy- 
drogen of that acid by chlorine, or converted acetic acid, C 4 H 3 3 +HO into 
chloracetic acid C 4 Cl 3 3 4-HO, without altering the capacity of saturation of 
the acid, or its combining measure in the state of vapour.! Decomposed by 
alkalies, these two acids give likewise analogous products, acetic acid yielding 

* Malaguti, Annales de Chimie, etc. t. 74, p. 299. 
t Philosophical Magazine, 3rd Series, vol. 18, p. 372. 
t Annales de Chimie et de Physique, tome 73, p. 77. 



SUBSTITUTIONS OF CHLORINE FOR HYDROGEN.. 493 

carbonic acid C o , with light carburetted hydrogen, C 2 H 4 , and chloracetic 

TT 

acid yielding carbonic acid C 2 4 with chloroform C 2 ^, ; the body last men- 
tioned being viewed as carburetted hydrogen in which three atoms of hydro- 
gen are replaced by three of chlorine. 

Many similar cases of the substitution of chlorine for hydrogen have been 
observed, but those already adduced are sufficient to illustrate the mode of 
replacement, and to prove that a compound may preserve its leading chemical 
characters, although its hydrogen be exchanged for chlorine. Chemists were 
not prepared for the admission of this equivalency of chlorine and hydrogen 
from any thing observed in inorganic compounds. The two elements seemed, 
indeed, to be strongly contrasted, chlorine typifying the electro-negative or 
salt-radical class of elements, and hydrogen belonging, incontestably, to the 
electro-positive or basyle class with the metals, although not occupying a high 
place in that class. One equivalent of chlorine being also isomorphous with 
two equivalents of manganese, to which latter element hydrogen appeared to 
be related, as a member of the magnesian family, the isomorphous relation to 
be looked for was one of chlorine with two of hydrogen, and not with one of. 
hydrogen as in oxamethane and chloroxamethane lately commented upon. 

But it is to be remembered that no body is absolutely chlorous (electro* 
negative,) or zincous (electro-positive,) but only relatively so to certain other 
bodies. Hence although zincous to chlorine, hydrogen is chlorous to carbon, 
or hydrogen is the chlorous constituent of the organic compounds in question. 
Even among inorganic compounds, we have instances of hydrogen discharging 
the same function, as in the class of phosphuretted hydrogen and arsenietted 
hydrogen, where 3 atoms of hydrogen are chlorous, and may be replaced by 
oxygen, chlorine, etc. (In ammonia, on the contrary, nitrogen appears to be 
the negative, and hydrogen the positive constituent.) In this way that uni- 
versal dualism in the constitution of a compound, or distribution of its ele- 
ments into two opposed classes, conducing to binary combination, which has 
never ceased to be a recognised doctrine of chemical science, in some form or 
other, with reference to inorganic compounds, is extended also to organic com- 
pounds. Such a doctrine which might always have been maintained on ab- 
stract grounds appears now to be inevitable from the observed substitutions of 
chlorine for hydrogen. Hydrogen then being viewed as a chlorous element 
in such compounds as carburetted hydrogen and oleiiant gas, while carbon is 
the basyle or zincous element, the former element may, therefore, be replaced 
by other bodies higher than itself in the scale of salt-radicals, such as chlorine, 
without any essential derangement of the constitution of the original compound. 
The equivalent substitution of chlorine for hydrogen is thus admitted in its 
full extent. This substitution appears to confirm and extend what is gene- 
rally understood at the electro-chemical distribution of elements, * on which 
our ideas of binary combination are founded, and not to be opposed to or in- 
compatible with such views. 

The isomorphism of chlorine and hydrogen, equivalent for equivalent, if 
confirmed, will cause the removal of the latter element from the magnesian 
class, but establishes a relation between hydrogen and silver, and therefore 
places the former on the verge of the potassium group. Hydrogen certainly 
possesses many relations to mercury, if not absolutely isomorphous with that 
metal (page 453.) 

By a chemical type M. Dumas understands a certain number of elements 
combined together, every one of which, whatever be its nature, may be re- 
placed by another, and indeed every one in its turn, so that not a trace of the 

* [See end of volume. R.B.J 
42 



494 PRELIMINARY OBSERVATIONS. 

original compound may remain. The arrangement of the elements in regard 
to each other remains always the same, and that is the character of the type. 
Thus all the chlorinated compounds derived from hydrochloric ether, including 
perchloride of carbon, contain ten atoms, which are supposed to have the same 
arrangement as in hydrochloric ether itself. Aldehyde produced by the par- 
tial oxidation of alcohol, and chloral by the action of chlorine upon alcohol, 
contain the same number of atoms and belong to one type: 

Aldehyde, C 4 H 3 0-f-HO, or C 4 H 4 2 . 
Chloral, C 4 Cl 3 0-fHO,orC 4 g 1 30 2 

When on the other hand, an atom is withdrawn from a compound without 
being replaced by another, the atoms which remain cannot retain their original 
position, and a new type must result. It is supposed by Dumas, that chlorine 
may replace carbon, nitrogen and other elements besides hydrogen, and any 
one element, indeed any other, without destruction of the primitive type. 
Such substitutions, however, have not been effected, and on the view of sub- 
stitution taken above are not to be expected, for carbon at least must always 
be considered as the basyle or electro-positive constituent of organic com- 
pounds, and never like oxygen, nitrogen and hydrogen, as chlorous or electro- 
negative. Even where chlorine replaces hydrogen, the type is not uniformly 
preserved, for we find occasionally the same body derived by substitution 
from two different types, as perchloride of carbon from both Dutch liquid and 
hydrochloric ether. 

The reference of bodies to a common type has often an advantage over their 
classification under a common radical or according to any theory of constitution, 
as it involves less that is speculative. The former asserts only that the bodies 
contain the same number of atoms and have a common constitution, but says 
nothing as to what that constitution is. Hence a type may be denoted by an 
empyrical formula of the simplest kind expressing nothing but the elements 
and their number, in which changes by subtitution can be distinctly exhibited. 
It is useful, in the present uncertain state of our knowledge respecting the 
constitution of organic compounds, to have such a mode of expressing com- 
pounds, and exhibiting their relations in composition, but it does not super- 
sede rational theories of constitution. 



TRANSFORMATIONS OF ORGANIC SUBSTANCES. 



ACTION OF FERMENTS, 

Complex organic substances frequently divide themselves into two or more 
compounds of a simpler constitution, without the intervention of any intelligi- 
ble chemical agency. The presence of a second organic substance, however, 
is an essential condition of such transformations, although the latter sub- 
stance does not contribute to the change by imparting any new element 
to the decomposing body, nor by abstracting any element from it. The re- 
solution of sugar into carbonic acid and alcohol in fermentation, by the contact 
of yeast, is a familiar example of such a change. Decomposition of this 
kind has been distinguished as catalysis, and the second body which deter- 
mines the changes in the first, by an action of presence, termed the catalytic 
agent (page 155.) The recent study of such decompositions has revealed 



ACTION OF FERMENTS. 495 

the circumstance that the activity of the catalytic agent is connected with 
its being itself in a state of decomposition at the time. The yeast is only 
active when, by access of air, it has become subject to oxidation, and the 
decomposition of the sugar is looked upon by M. Liebig as a reflex action 
of the decomposition of the yeast. The views of that eminent philosopher on 
the action of yeast and other ferments will be best explained in his own 
words. 

" This action may be expressed by the following law, long since proposed 
by Laplace and Berthollet, although its truth with respect to chemical pheno- 
mena has only lately been proved. ' A molecule set in moiion by any power 
can impart its own motion to another molecule with which it may be in con- 
tact/ " 

This is a law of dynamics, the operation of which is manifest in all cases, 
in which the resistance (force, affinity, or cohesion,) opposed to the motion 
is not sufficient to overcome it. 

We have seen that ferment or yeast is a body in the state of decomposition, 
the atoms of which, consequently, are in a state of motion or transposition. 
Yeast placed in contact with sugar, communicates to the elements of that 
compound the same state, in consequence of which, the constituents of the 
sugar arrange themselves into new and simpler forms, namely, into alcohol 
and carbonic acid. In these new compounds the elements are united together 
by stronger affinities than they were in the sugar, and therefore under the 
conditions in which they were produced further decomposition is arrested. 

We know, also, that the elements of sugar assume totally different arrange- 
ments, when the substances which excite their transposition are in a different 
state of decomposition from the yeast just mentioned. Thus, when sugar is 
acted on by rennet or putrefying vegetable juices, it is not converted into 
alcohol and carbonic acid, but into lactic acid, mannite, and gum. 

Again, it has been shown, that yeast added to a solution of pure sugar gra- 
dually disappears, but that when added to vegetable juices which contain 
gluten as well as sugar, it is reproduced by the decomposition of the former 
substance. 

The yeast with which these liquids are made to ferment, has itself been 
originally produced from gluten. 

The conversion of gluten into yeast in these vegetable juices is independent 
on the decomposition (fermentation) of sugar; for, when the sugar has com- 
pletely disappeared, any gluten which may still remain in the liquid, does not 
suffer change from contact with the newly-deposited yeast, but retains all tl.o 
characters of gluten. 

Yeast is a product of the decomposition of gluten ; but it passes into a se- 
cond stage of decomposition when in contact with water. On account of its 
being in this state of farther change, yeast excites fermentation in a fresh solu- 
tion of sugar, and if this second saccharine fluid should contain gluten, (should 
it be wort, for example,) yeast is again generated in consequence of the trans- 
position of the elements of the sugar exciting a similar change in this gluten. 

After this explanation, the idea that yeast reproduces itself as seeds reproduce 
seeds, cannot for a moment be entertained."* 

To these may be added the results of the very recent inquiries of MM. Bou- 
tron and Fremy on the phenomena of the fermentation of malt. These chemists 
find that the same azotised matter in the grain, which acts as the ferment, 
passes through a succession of changes, and can excite different kinds of fer- 
mentation at different stages in the progress of its decomposition ; that it is not 

* Liebig's Organic Chemistry in its applications to Agriculture and Physiology, edited 
by Dr. Lyon Play fair. 



496 PRELIMINARY OBSERVATIONS. 

one but a series of ferments. It is as diastase that it at first appears, or this is 
the first condition of the ferment in the infusion of malt, as is proved by the ac- 
tion which it exerts upon starch, the latter being converted into sugar. From 
the acidity of the liquor which is afterwards observed, it is evident that the azo- 
tised matter next takes the character of the lactic ferment, and converts the 
sugar, to a certain extent, into lactic acid. A period then arrives at which the 
liquid, still transparent, becomes turbid, and the resulting precipitate is the mat- 
ter which can produce the alcoholic fermentation ; and it is only at this epoch 
that alcohol is formed and carbonic acid disengaged. That it is the insoluble 
precipitate to which the alcoholic fermentation should be ascribed, is proved by 
filtering the liquid to separate the ferment, when the alcoholic fermentation is 
immediately arrested * 

The action of yeast and all other ferments is destroyed by the temperature 
at which water boils, by alcohol, by acids, salts of mercury, sulphurous acid, 
chlorine, iodine, bromine, by aromatic substances, volatile oils, and particularly 
empyreumatic oils, smoke and a decoction of coffee, these bodies in some cases 
combining with the ferments or otherwise effecting their decomposition. 

The following are additional instances of fermentation. The smell and taste 
which distinguish wine from all other fermented liquids depend upon cenanthic 
ether, which contains a peculiar acid ; and those of spirits from corn or potatoes 
upon a peculiar oil, the oil of potatoes. Both of these substances are produced 
in fermentation, the former probably from the tartaric acid of the wine, the lat- 
ter by a simultaneous decomposition of the cellular tissue of the grain or potato. 
The oil of potatoes has all the characters of an alcohol. The production of this 
oil is completely prevented in the fermentation of beer, by the presence of an 
aromatic substance, the volatile oil of hops. In the fermentation of the Herba cen- 
tauriwm minor-ins, a plant which possesses no smell, a true ethereal oil is formed, 
of a penetrating agreeable odour. The leaves of tobacco, when fresh, have lit- 
tle or no smell, and when distilled, yield a white, fatty, crystaliizable substance 
(nicotianine,) which contains no nitrogen and is quite destitute of smell. But 
when the same plant, after being dried, is moistened with water, tied together 
in small bundles, and placed in heaps, a peculiar process of decomposition takes 
place. Fermentation commences, and is accompanied by the absorption of 
oxygen ; the leaves now become warm and emit the characteristic smell of pre- 
pared tobacco and snuff. When the fermentation is carefully promoted, and too 
high a heat avoided, this smell increases and becomes more delicate ; and after 
the fermentation is completed, an oily azotised volatile matter, called nicotine, 
is found in the leaves. This substance which possesses all the properties of a 
base, was not present before the fermentation. The different kinds of tobacco 
are distinguished from one another, like wines, by having very different odori- 
ferous substances, which are generated along with the nicotine (Liebig.) 

M. Liebig also ascribes the morbific action of matters of contagion and mi- 
asms, to their operation as ferments. He applies the law already quoted to 
organic substances forming part of the animal organism. " We know that all 
the constituents of these substances are formed from the blood, and that the 
blood by its nature and constitution is one of the most complex of all existing 
matters." 

Nature has adapted the blood for the reproduction of every individual part 
of the organism; its principal character consists in its component parts being 
subordinate to every attraction. These are in a perpetual state of change or 
transformation, which is effected in the most various ways through the in- 
fluence of the different organs. 

* Ann, de Chim., &c„ 3 serie, I. 2, p. 269. 



MOLECULAR THEORY OF ORGANIC COMPOUNDS. 497 

The individual organs, such as the stomach, cause all the organic sub- 
stances conveyed to them which are capable of transformation to assume new 
forms. The stomach compels the elements of these substances to unite into 
a compound fitted for the formation of the blood. But the blood possesses no 
power of causing transformations; on the contrary, its principal character con- 
sists in its readily suffering transformations; and no other matter can be com- 
pared in this respect with it. 

Now it is a well-known fact, that when blood, cerebral substance, gall, pus r 
and other substances in a state of putrefaction, are laid upon fresh wounds; 
vomiting, debility, and at length death, are occasioned. It is also well known 
that bodies in anatomical rooms frequently pass into a state of decomposition 
which is capable of imparting itself to the living body, the smallest cut with a 
knife which has been used in their dissection producing in these cases danger- 
ous consequences. 

The poison of bad sausages belongs to this elass of noxious substances. 
Several hundred cases are known in which death has occurred from the use of 
this kind of food. In Wirtemberg especially, these cases are very frequent, 
for there the sausages are prepared from very various materials. Blood, liver, 
bacon, brains, milk, meal and bread, are mixed together with salt and spices; 
the mixture is then put into bladders or intestines, and after being boiled is 
smoked. When these sausages are well prepared, they may be preserved for 
months, and furnish a nourishing savoury food; but when the spices and salt 
are deficient, and particularly when they are smoked too late or not sufficiently, 
they undergo a peculiar kind of putrefaction which begins at the centre of the 
sausage. Without any appreciable escape of gas taking place, they become 
paler in colour, and more soft and greasy in those parts which have under- 
gone putrefaction, and they are found to contain free lactic acid or lactate of 
ammonia; products which are universally formed during the putrefaction of 
animal and vegetable matters. 

The death which is the consequence of poisoning by putrefied sausages 
succeeds very lingering and remarkable symptoms. There is a gradual 
wasting of muscular fibre, and of all the constituents of the body similarly 
composed. 

Sausages, in the state here described, exercise an action upon the organism, 
in consequence of the stomach and other parts with which they come in con- 
tact not having the power to arrest their decomposition; and entering the blood 
in some way or other, while still possessing their whole power, they impart 
their peculiar action to the constituents of that fluid. 



MOLECULAR THEORY OF ORGANIC COMPOUNDS. 

It is observed by Liebig that in all organic compounds it is necessary to 
consider two kinds of attraction, that of the contained radicals, and that of the 
ultimate' elements themselves for each other; which last attraction is not 
superseded by the former. To these elemental attractions we are to look for 
an explanation of the phenomena of substitution. 

Any theory of combination would be incomplete which did not provide in 
the constitution assigned to both elementary and compound bodies, for that 
propagation of chemical action to a distance which is witnessed in the voltaic 
circle. The consideration of that action has already forced upon us the con- 
clusion that even a free element such as a metal, in the state in which we ope- 
rate with it, has a complex molecular structure, its atoms being grouped, so as 
to represent binary compounds. Hence in combining two different elements, 

42* 



498 PRELIMINARY OBSERVATIONS. 

we have really to undo a previous but weaker combination in both cases, be- 
fore the dissimilar elements unite; and consequently, even where combination 
appeared most direct, we have the compound really formed by a mutual 
double decomposition, or by the substitution of one element for another in 
pre-existing frames of compounds. The universal susceptibility of com- 
pounds of all kinds to decomposition under electrical action of high intensity, 
appears also to argue a greater simplicity and sameness of constitution of 
chemical compounds than is generally recognised. 

We are repelled by the idea of atoms of the same kind having the relation to 
each other of combination, for diversity of nature appears to be the reason why 
bodies combine. The intensity of the combination certainly increases with the 
diversity, but this does not prove that such diversity is an essential condition of 
combination. Combination, indeed, appears to be the natural condition of 
matter, the source of its cohesion and aggregation, which it retains by inertia, 
and decomposition to require the application of a force, such as the communica- 
tion of heat to atoms which supplies them with the repulsive power required to 
overcome their combination. 

The fundamental elemental combination of every compound is assumed to 
be binary, one element being chlorous (negative,) and the other zincous or 
basic (positive ;) or one set of the elements being chlorous, and another set 
basic. This difference in the character of the elements of a compound may be 
expressed by writing its formula in two lines, placing the basic or positive ele- 
ments in the lower, and the chlorous or salt-radical elements in the upper line : 

Water _, carbonic acid -J?, hydrate of potash _L_ , carbonate of potash _*! > 
H C K.H C .K 

defiant gas _ ±, or _2 — i ; ether _L_, alcohol _i 

C 4 C 2 .C 2 C 4 C 4 H. 

Most of these formulas are meant only to express that certain elements col- 
lectively are chlorous and certain others collectively basic. In ether, for instance, 
4 atoms (C 4 ) are basic, against 6 atoms (H.O) chlorous; but it is to be supposed 
that many compounds admit of a division into more simple binary compounds, 

TT IT TT 

olefiant gas — - into two binary compounds 2C 2 H 2 , expressed thus, _£ — £- 
C 4 C 2 .C 2 

TT TT TT TT 

or even four binary compounds 4CH, expressed thus, ' — No particular 

binary arrangement of this kind, however, is at present insisted upon, unless in 
a few cases. All that is assumed is: 

1 . That the basic or positive element or elements are in immediate combina- 
tion with the chlorous element or elements placed above them in the formulas. 

2. That these binary compounds again are associated together so as to form 
the compound molecule, from an attraction of all the basic elements for each 
other, and of all the chlorous elements for each other, of such a nature as retains- 
together the 3 atoms of the same kind which form a single equivalent of nitrogen 
or phosphorus, the 3 atoms of cyanogen in cyanuric acid, the various multiples, 
of C 2 H 2 grouped together in the molecule of olefiant gas and hydrocarbons 
isomeric with it, or the multiples of C 5 H 4 in the molecule of oil of turpentine 
and a large class of essential oils. Ji complex organic molecule is thus repre- 
sented as an association of two or more binary compounds, comparatively 
simple in constitution, often isolable substances and possessed of considerable 
stability. 

In the superior or chlorous portion of the formulas of organic compounds we 
may generally expect to find chlorine, oxygen, nitrogen, hydrogen ; and in the 
inferior or basic portion, carbon, or carbon and hydrogen. The former ele- 
ments appear to be chlorous in the order in which they are enumerated : 



MOLECULAR THEORY OF ORGANIC COMPOUNDS. 499 

Chlorine 

Oxygen 

Sulphur 

Nitrogen 

Hydrogen. 

We find in substitutions, those in the lower part of the table replaced by those 
above them, hydrogen at the bottom of the table eminently so by chlorine at 
the top, and hydrogen also by oxygen. Nitrogen less frequently interferes, but 
it appears in certain cases more chlorous than oxygen and to replace that ele- 
ment; only, however, in certain double decompositions as an element of am- 
monia, which are not sufficient to determine its place, as oxygen might be 
placed above chlorine from similar indications, as the conversion of chloroform 
F0CI3 into formic acidFo0 3 by potash. 

Compounds of the same type. — These are bodies which have the same num- 
ber of elementary atoms, and the same numbers of them chlorous and zincous. 
As: 

TT pi 

Of defiant gas type: defiant gas — f; chloride of carbon _ 1. 

C 4 C 4 

HO H CI 

Of ether type: ether — f— ; chloride of ethyl _i — ; chlorinated ethyl 
C 4 C 4 

Of alcohol type: alcohol 5 ' ; acetic acid \ 3 * • chloracetic acid 
C 4 . H C 4 . H 

Cl3O.rO 

C 4 . H* 

^ u . . : ,, . . H3O.O . , CI, 0.0 

Of aldehyde type : aldehyde 3 ; choral -f — -• 

C 4 . H C 4 . H 

N 
Ammonia. — The molecular formula of ammonia appears to be — , and not 

^3 
H 

— -. The hydrogen of ammonia being basic, according to the first formula, 

should not be replaced by chlorine, and certainly chlorinated salts of ammonia, 
analogous to the chlorinated compound ethers, have not been observed. Our 
knowledge of the composition of the explosive chloride of nitrogen is not suffi- 
ciently certain to decide the question. It will be remembered that N in the 
formula above is equivalent to O s or H 3 . Wohler's white precipitate of mer- 
cury HgCl+NH 3 (page 453,) and ordinary white precipitate, HgCl-fHgNH , 

• m x 1 u • j .- , L CI. N , CI. N 

are assimilated, being expressed respectively by : - — — -. and -. 

Hg.H 3 ' Hg.H 2 Hg 

The black compound, produced by solution of ammonia upon calomel, is 

* l CI. N ., , , ClHff. N _ 

expressed by — — — -— — , or possibly by - — J; . Thus amidogen is not 
tig 2 ti 2 tig 2 tig 2 .t± 2 tig 

necessarily present in the supposed metallic amides ; but appears to be more 

necessary to the constitution of oxamide and urea, particularly the last. Of 

oxalate of ammonia, and oxamide, the molecular formulae are : — 2— : — an( j 

C„.H.H 3 
0„.N " 3 



C 2 .H 2 



N 
Cyanogen and cyanides. — The formula for cyanogen is — ; for hydrocyanic 



c* 



500 PRELIMINARY OBERVATIONS. 

NH N 

acid , and not —j^. That the hydrogen of hydrocyanic acid is chlorous 

C 2 C 2 H 

and not basic, appears in its being replaced by chlorine, with formation of 

NCI 

hydrochloric acid and the chloride of cyanogen, Hence, also, the little 

C 2 
action of potash and strong bases upon hydrocyanic acid its hydrogen, 
unlike that of ordinary hydrogen acids, being chlorous, while the same hydro- 
gen is readily replaced by the more chlorous metals, such as mercury, the 

cyanide of mercury being - . The latter salt is not decomposed by strong 

2 

acids, as it would be if its constitution resembled that of cyanide of potassium 

N 

But cyanide of mercury is readily decomposed by sulphur and sulphu- 

C 2 K 

retted hydrogen, and by hydrochloric acid, sulphur and chlorine assuming the 

mercury and forming sulphuret and chloride of mercury respectively, while 

hydrogen is left in the place of the abstracted mercury, and hydrocyanic acid 

NH , , 

— reproduced. 

The two atoms of cyanide of hydrogen, which exist in ferrocyanic acid, 
FeCy-f2HCy, have on the contrary, the constitution of an ordinary hydrogen- 
acid, the hydrogen being strongly basic and easily replaced by the basic metals, 

N 
potassium, &c, while the iron is not. It thus contains L • But the iron of 

C 4 H 2 

the associated cyanide of iron not being precipitated by potash (replaceable by 
potassium,) must be chlorous ; and this metallic cyanide, therefore, resembles 

ordinary hydrocyanic acid in constitution, or is -. 

TV 

Ferrocyanic acid . . . 
Ferricyanide of potassium 

The molecular formulae for ferricyanic acid (H 3 +Fe 2 Cy 6 ,) and for ferri - 
cyanide of potassium (K 3 +Fe 2 Cy 6 ,) deducible from the'same principles, are: 



Ferricyanic acid . t . 
Ferricyanide of potassium 



NS 
Assigning to sulphocyanogen, C 2 NS 2 , the molecular formula -~A, its 

compounds will be: 

N S 
Hydrosulphocyanic acid . . ? 

C 2 H 

Sulphocyanide of potassium . N S 2 

C 2 K 

Hydrated cyanic acid and cyanate of potash will be represented by formulae 
which assimilate them to the preceding compounds: 



i\r e 


• ^t 


c 2 

NFe 


• C 4 H 2 

. N 2 


c a 


. C 4 K 2 



N,Fe, 


. N 3 


c 6 

N 3 Fe 2 


• C 6 H 3 

. N 3 


c 8 


• C 6 K 3 



MOLECULAR THEORY OF ORGANIC COMPOUNDS. 501 

NO 

Hydrated cyanic acid . . V 

C 2 H 

Cyanate of potash . . . NQ 2 

C 2 K* 

The^ two isomeric bodies cyanate of ammonia and urea have different 
molecular formulae: 



Cyanate of ammonia . 
Urea 



N Q 2 .N 
C, H .H 3 
N~.O a .N 
C 2 .H 2 .H 2 



In the last formula urea is represented as containing 1 atom of cyanogen, % 
atoms of water and 1 atom of amidogen. According to the more common 
opinion, it contains 2 atoms of carbonic oxide and 2 atoms of amidogen, a 
view which may be expressed by making a slight change in the upper line of 
the preceding formula: 

Urea ®»*g . 

C 2 .H 2 .H 2 

But the existence of cyanogen in urea being probable, the first formula is 
preferable. Urea may then be compared with allantoin, which contains 2 
atoms of cyanogen and 3 atoms of water: 

Allantoin . . . £t°. -» N °. N 



C 4 H 3 C 2 .H 3 .C a 

Doubling the atom of allantoin, that substance and its compound with oxide 
of silver will be: 

^Land N ^°« 
C 8 .H 6 C 8 .H 5 Ag 

From the different action of potash upon the isomeric bodies, Dutch liquid 
and protochlorinated chloride of ethyl, there can be little doubt but their mole- 

TT pi pi 

cular formulae are really different: Dutch liquid -~ — '—', protochlorinated 

4 . H 

TT pi 

chloride of ethyl —^ — * and while the other chlorinated compounds of chlo- 
ride of ethyl are ^ ? and a ^ tho3e of olefiant gas> i somer ic with the 

TT Ql pi 

preceding, are, as appears by the action of an alkali, I-f — ^— and 

C 4 . H, 
HOI PI 
-p — ~j-. For from Dutch liquid and the last two mentioned compounds, 

potash withdraws HC1, and liberates three compounds of the same type: 
H3CI H.C1, „„, HC1 3 

° 4 c 4 c 4 • 



502 PRELIMINARY OBSERVATIONS. 

The elements which are chlorous together or basic together in a compound, 
certainly exert an influence upon each other, although they are not to be sup- 
posed to be combined, as those of different name are with each other. For 
we find a tendency among them to arrange themselves in pairs. Thus the 
chlorinated compound of oxide of ethyl, most readily formed, is that of which 

H CI O 

the empyrieal formula is C 4 H 3 C1 2 0, and the molecular formula — —-^2 — f 

or rather — I — I , of which the three atoms of hydrogen are associated 

with three still more chlorous atoms, namely two of chlorine and one of oxy- 
gen. There can be no doubt that these three remaining atoms of hydrogen 
are thus in some degree defended from the -farther action of chlorine, and less 
easily removed than the other two. 

The molecular formula of oil of bitter almonds, or hydruret of benzoyl 

appears to be — - — I; of hydrated benzoic acid _i — 1L_ 
C 14 C 14 * H. 

tt r\ 

Of the oil of spircea or salicylous which is isomeric with the last — 5_i ; of 

C 14 H 

chlorosalicylous acid, _ 4 4 ; and of hydrated sylicic acid, 5 6 , or 

C. 4 H C l4 H 

H 5 5 .0 

C 14 .H * 

The peculiarity of oil of spiraea, or salicylous acid, is that its single basic atom 
of hydrogen is removeable by itself, like that of a hydrogen acid, in the formation 
of salts, while of hydrated benzoic acid, both H and O are removed in the 
formation of salts. This difference is expressed in their molecular formulae. 

The hydrated and bibasic bromobenzoic acid is an association of two acids, 
one of which differs from the other in having an atom of hydrogen replaced by 
bromine ; namely HO-f C 14 H 5 4 and HO-f-C 14 H 4 Br0 4 . Of these two the 

molecular formulae may be, of the first, 5 4 '- and of the second— i— 2 — ' 

C 14 .H G 14 . H 

Of benzamide, Bz+Ad, or C 14 H.0 2 +NH 2 , the molecular formula may be 
5 ' 2 J in which N replaces 30 of hydrated benzoic acid. 

°14 H 2 

Of hydrobenzamide, C l4 H 6 N§, produced by the action of ammonia on the 

H N 2 - 
hydruret of benzoyl, the molecular formula is — £ — -; or that of the oil, with 20 

replaced by N|- 

Of sulicylimide, HO-fC 14 H 5 ON§, produced by the action of ammonia on 

H O N 2 H N 2 0.0 
salicylous acid, —^ — \~ y or — * — - — '—-, that is, salicylous acid with 20 replaced 

C 14 H C 14 ' H 

by N|, 
Of chlorosalicylhnide, C 14 H 3 C1 3 2 N§, H 2 C] 3 N I Q 2) or Cl 3 H,O a Nf ; 

three atoms of the chlorous hydrogen of salicylimide being replaced by chlorine. 

TT 

Formation of acids. — The formula of benzole or benzin, is ; of the 

Vl2> 

TT ^IO IT O 

neutral body, sulphobenzide, -A 1, or _i — L. To the last hydrated sulphuric 

C 12 C 12 S 

acid is attached, in sulphobenzic acid = 5 3 " — H-, or 



C la S.S. H C l2 ,S.H 



MOLECULAR THEORY OF ORGANIC COMPOUNDS. 503 

Sulphurous acid, S0 2 , is a body like sulphobenzide; in hyposulphuric acid 

it has hydrate of sulphuric acid attached to it. Sulphurous acid, — 2;hydrated 

S 

hyposulphuric acid, "L H_ . 

' S. S. H 

The neutral substance, benzile C 14 H,0 2 , or C^H. 4 , becomes benzilate 

H O 
of potash, by fixing the elements of hydrate of potash ; thus benzile,— ^—i; 

benzilate of potash, — 10 ** ' . When the potash is withdrawn from the lat- 
C 28 . H.K 

ter by a stronger acid, hydrated benzilic acid, is formed, — — — il_l_ . When 

C 28 . H.H 

neutralized with bases, this hydrate loses an atom of water and acquires an 

atom of metallic oxide in its place. 

Chlorisatin, a neutral substance, when dissolved in caustic potash is con- 



verted into chlorisatinate of potash in a similar manner: Chlorisatin, 



H CIO3N 



O 

chlorisatinate of potash, _i— — ? ' ' • Decomposed by a strong acid, the lat- 
C 1 6 H.K 

ter salt gives hydrate of chlonsatinic acid, — ^ — — 

C l6 . H.H 

Concentrated acids decompose this hydrate, assuming its water, and repro- 
duce the neutral chlorisatin. It is clear that the anhydrous acids generally such 
as S0 3 , P0 5 , &c., belong to the class of sulphobenzide and chlorisatin, and owe 
their power of combining with bases to the association with them of an atom of 
water. 

Hydrate of sulphuric acid,— ^_ • hydrates of phosphoric acid, _^ ** » 

S. H 1 P.H, P.H 2 

and^2l. 
P.H 3 

We have other series of compounds of which the members only differ from 
each other, in containing different proportions of water or its elements attached 
to a common basis, as starch, gum and starch sugar ; gum being starch plus 1 
atom of water ; and starch sugar, starch plus 2 atoms of water. It is at present 
impossible, however, to assign a probable molecular formula to the basis of the 
starch and many other series of compounds from our ignorance of the function 
of the hydrogen in their constitution, where the hydrogen has not been replaced 
by another element more decidedly chlorous or basic in its character. 



504 AMYLACEOUS AND SACCHARINE SUBSTANCES. 



CHAPTER II. 

SECTION I. 

AMYLACEOUS AND SACCHARINE SUBSTANCES. 
STARCH. 

Syn. FficuLA, amylin; C 12 H 10 O, e ; in combination with oxide of lead, 
C 12 H 9 9 -j-2PbO, (Payen.) Its composition, well dried in vacuo at 212°, is 

12 atoms of carbon 917.22 . 44.91 

10 atoms of hydrogen. » 125.00 . 6.11 

10 atoms of oxygen 1000.00 .48.98 



2042.22. 100.00 



Starch is separated from a variety of vegetable substances containing it, from 
the grains of the different cereals, many roots such as the potato, the stems of 
many monocotyledonous plants particularly the palms, and from several lichens. 
It is contained in the cavities of the vegetable cells, in the form of small white 
and brilliant grains, which are not crystalline, but have a rounded outline with- 
out any determinate form. It is so far an organized substance, that each grain 
has a species of envelope, which resists the action of cold water, while the inner 
portion is observed by the microscope to be composed of concentric layers of 
unequal thickness, as if the layers produced during the day exceeded in thick- 
ness those formed during the night. (Fritzsche.) The grains of the starch of 
different plants differ in size, those of the potato being -^ 9 , of wheat -gfo of 
millet, jo^oo th of an inch in diameter, according to observations of Raspail. 
But it is also known that the starch grains of the same plant differ in size at 
different stages of its development. 

The purest starch is obtained from potatoes, which are reduced to a pulp and 
washed on a sieve. The grains of starch are separated and passed through ; 
they may be washed repeatedly with cold water. Potatoes yield 15 to 17 per 
cent, of starch ; wheaten flour consists essentially of starch and another vegetable 
principle gluten. When made into dough with a little cold water, inclosed in a 
linen bag, and gently pressed by the hand in water, so long as a milky juice ex- 
udes, these two substances are in a great measure separated, the gluten remain- 
ing in the bag, and the grains of starch being diffused through the water, from 
which they afterwards subside. On the large scale, wheaten meal coarsely 
ground is mixed with cold water in large vats, in which, with a certain addition 
of sour water from a former process, the liquid ferments for seven or eight 
days, and the starch subsides. The acetic formed in the fermentation dissolves 
the greater part of the gluten of the flour, and the bran is separated from the 
starch by a fine sieve. The starch is afterwards mixed with pure water in the 



GELATINOUS STARCH OR AMIDIN. 505 

vat and allowed to settle ; the remaining gluten is deposited as a gray slimy 
matter above the starch, which is removed, and the starch washed again till 
pure. For the fermentation, the action of a weak solution of caustic alkali has 
lately been substituted, by which the gluten of flour is dissolved and the starch 
left. Mr. O. Jones employs a ley containing 200 grains of caustic soda in one 
gallon of water. A ley containing 400 grains of soda causes the starch to 
gelatinize ; by that quantity of ley, one pound of excellent starch is obtained 
from flour of rice, allowed to digest in it in the cold for forty-eight hours. 

Arrow root is the starch from the root of the maranta arundinacea. It is 
not accompanied by any odoriferous principle, and has therefore no smell when 
boiled with water, in which respect it resembles potato starch washed with alco- 
hol. Sago is derived from the pith of true palms of the genus Sagus ; tapioca 
or cassava, from an American plant, the iatropha manihot, of which the milky 
juice, itself poisonous, deposits when diffused through water a harmless starch. 
The peculiar appearance and solubility in cold water of sago and tapioca arise 
from the starch being exposed while humid to a temperature above 140°, so 
that it is dried in the gelatinous condition and not in the original grains. 

Starch or fecula may be purified from adhering gluten by maceration in di- 
luted acetic acid, or by means of a cold and dilute solution of alkali. The starch 
of commerce is perfectly white, and in small columns formed by the contraction 
of the humid mass of starch in drying, which are easily reduced to a fine powder. 
It emits a particular sound when pressed between the fingers, its density is 1.53. 
The other characters which fecula exhibits are complete insolubility in cold 
water and in alcohol, but resolving itself in boiling water into a mucilaginous 
liquid, which forms a jelly on cooling. This when suddenly dried upon linen 
imparts considerable stiffness to it. Dilute acids dissolve starch, and form a 
transparent and highly fluid liquid. When this solution is boiled for a long 
time the starch is first converted into a body having the properties of gum, 
and afterwards into starch sugar. Nitric acid with the assistance of heat con- 
verts starch into oxalic and malic acids, without producing a trace of mucic 
acid. Starch is also soluble in alkalies ; when brayed with a concentrated so- 
lution of hydrate of potash, it forms a transparent gelatinous compound soluble 
in alcohol and water, from which the starch is precipitated by acids. Starch 
is precipitated from solution by lime-water and hydrate of barytes, and by sub- 
acetate of lead containing ammonia, forming insoluble compounds with lime, 
barytes and oxide of lead. A solution of starch is also coagulated by borax, 
which combines with and precipitates the starch, but not by boracic acid. 
Starch is precipitated by an infusion of gallnuts. It forms a blue insoluble 
compound with iodine. 

Gelatinous starch or amidin. — In this state starch appears to retain a por- 
tion of its organization or structure, upon which some of its properties depend, 
and which is the cause of the difference in properties of the varieties of starch, 
containing the same chemical principle. When grains of fecula are rubbed in 
a mortar with sand, their coating is broken and they form a grayish-white 
powder, which when mixed with a little cold water immediately expands and 
forms a transparent jelly. If the uninjured grains be thrown into water above 
140°, they imbibe water, swell and burst their envelopes, which have a cer* 
tain degree of elasticity, and undergo the same change. But the gelatinous 
starch has imbibed water like a sponge, without being dissolved and when 
placed upon several folds of blotting paper imparts to the latter its moisture, 
and dries up into a mass resembling horn, which exhibits again the same 
phenomena, when after being reduced to powder it is treated with boiling 
water. A portion of the gelatinous starch, however, appears to be dissolved 
by a large quantity of cold water, about £th of the starch, when the bruised 
grains are diffused through 100 times their weight of cold water, and the 
43 



506 AMYLACEOUS AND SACCHARINE SUBSTANCES. 

whole of it when gelatinous starch is boiled with 40 or 50 parts of water; for 
the mucilaginous liquid passes through a double paper filter and no granules 
or solid matter in any other form can be perceived in the liquid by the micro- 
scope. The tegumentary portion of the starch, which amounts to three or 
four thousands of the whole, remains on the filter, but may also be dissolved 
by continued boiling. When the quantity of starch dissolved by hot water 
is considerable, much of the starch separates in a gelatinous state, on the cool- 
ing of the solution. The peculiar character of the solution of starch in water 
has been the object of much research by M. Payen, which lead to the obser- 
vation that by the freezing of a solution of starch that substance separates from 
the water and contracts into a species of tissue, which is not dissolved again 
on the thawing of the ice. It is the opinion of the same chemist that the or- 
ganization of the starch is not altogether effaced or its cohesion destroyed, so 
long as it is gelatinous and possesses the property of being stained by iodine 
of a blue, or of different shades of violet to red, according to the degree of its 
division.* 

Granules of starch of M. Jacquelain. — When starch is heated under pres- 
sure in a Papin's digester to 302° (150° cent.,) with from five to fifteen times 
its weight of water for two hours, the whole is dissolved except the tegumen- 
tary matter, and the solution is so thin that it may be filtered at the boiling 
temperature. This solution when it cools deposites a considerable mass of 
pulverulent matter, white and opaque and entirely composed of a species of 
granules, first observed by M. Jacquelain. These granules when examined 
by a microscope having a power of 200 diameters, present themselves as cir- 
cular or spherical bodies, transparent, and uniformly -^y^o of an inch 
( T0 2 c¥ ths of a millimetre) in a diameter. When dried they have the white- 
ness of starch without its lustre. They are denser than water, and subside 
from that liquid almost as quickly as fecula. These granules are scarcely so- 
luble at 32°, slightly so at 53.6°, but dissolve in a considerable proportion 
about 158°, and in still greater quantity at the temperature of ebullition. This 
increased solubility is the most remarkable chemical change which the starch 
has undergone, by its solution in water at a high temperature. Anhydrous 
alcohol precipitates completely a solution of the granules and the aqueous 
solution of iodine makes it blue and not purple. When a film of a concen- 
trated solution of these granules is left under the microscope, it is seen to be 
in a state of agitation so long as the evaporation of the water continues and 
when the matter comes to be dried, the granules cease to be visible, attaching 
themselves to each other as if soldered together, and forming a transparent 
plate in which nothing can be perceived even with a magnifying power of 
800 diameters. A solution of the granules, when frozen and afterwards 
melted, gives the granules in the form of fine filaments, which are very 
short, and have a silky lustre. M. Jacquelain finds these granules and fecula, 
both dried between 266° and 275°, to have the same composition, C l2 H l0 
O 10 . But he constantly obtained a small quantity of nitrogen from starch, 
about | per cent, from his granules and a somewhat larger proportion from fe- 
cula, which he conceives to be essential to that substance. The power which 
starch possesses to form these granules, must be considered as an organic 
property, and proves that it retains contractility even when dissolved in wa- 
ter.} The original grains of fecula, which consist of concentric layers, are 
still more highly organized; starch indeed occupies an important place in or- 
ganic chemistry, as a link between matters truly organized and those bodies 
of a less complex constitution, which still belong to the organic kingdom, but 

* Annates de Chimie et de Physique, tome 65, p. 225. 

t Jacquelain, Annates de Chimie et de Physique, tome 73, p. 167. 



DEXTRIN OF MUCILAGINOUS STARCH. 507 

approach in their crystallization, volatility or chemical properties to mineral 
substances properly so called. 

A compound of amidin and oxide of lead was formed by M. Payen, by dis- 
solving two parts of pure starch in 250 parts of water, with ebullition for twenty 
minutes and pouring the filtered solution into an excess of the ammoniacal so- 
lution of acetate of lead (page 412,) collecting and washing the precipitate upon 
a filter, and drying it in vacuo at 356° (180° cent.) He terms it the bibasic 
amylate of lead, C 12 H 9 O fl -f 2PbO. 

Starch combines with chlorine, bromine and iodine. The solution of chlo- 
rine has little effect upon starch, but when dry starch is introduced into chlo- 
rine gas, the latter is absorbed, a little carbonic acid is evolved, the mass 
becomes liquid, assumes a brown colour, and is charged with much hydro- 
chloric acid. The bromide of starch is an orange powder, which is formed, 
according to Fritzsche, when water saturated with bromine is dropped into a 
solution of starch in water acidulated with hydrochloric acid. The colour is 
destroyed by a slight heat; to obtain the iodide, of starch in a state of purity 
the following process is recommended. A firm jelly is prepared by boiling 
potato starch with water, and after cooling, a quantity of hydrochloric acid is 
added sufficient to occasion the mixture to become liquid when assisted by a 
slight elevation of temperature. The solution is then filtered and a solution of 
iodine in alcohol is mixed with it, so long as the latter produces a blue precipitate, 
care being taken not to add too much of the solution of iodine, as the alcohol of 
that solution will then precipitate uncombined starch. The precipitate is col- 
lected, drained on a filter and washed with water poured upon it in small quanti- 
ties. Once deprived of hydrochloric acid, the compound dissolves in the water 
used to wash it ; the washing is therefore interrupted so soon as the liquid which 
passes exhibits an intense blue colour; the compound is removed from the fil- 
ter and dried on a capsule over sulphuric acid in vacuo. A brown-black gum- 
my and very brilliant mass is thus obtained, which can easily be pounded when 
perfectly dry, but which becomes viscous by attracting hygrometric moisture. 
It is very easily dissolved by water, giving a deep blue solution, and may be 
recovered again by evaporation in vacuo, in a dry state and without alteration. 
When a solution of iodide of starch is heated, it becomes colourless at 158^ 
or 160° if very dilute, but not under 194° when the solution is concentrated. 
The colour reappears on the cooling of the solution, provided it has not been 
boiled. When the colour is not restored, the iodine appears to be converted 
into iodic and hydriodic acids. Animal charcoal discolours the blue solution, 
carrying down iodine. The iodide of starch contains 41.79 parts of iodine with 
58.21 of starch, according to the analysis of Lassaigne, or it consists of two 
atoms of iodine with one atom of starch. (Berzelius.) 

Dextrin or mucilaginous starch. — By the action of acids, alkalies, diastase, 
and of heat, a complete dissolution of the gelatinous starch may be effected ; it 
becomes largely soluble in cold water, the solution is mucilaginous and not 
gelatinous, and the altered starch has many of the characters of gum. Dextrin 
is prepared by boiling a solution of starch with a few drops of sulphuric acid, 
or by heating to 200°, 100 parts of starch, 20 of sulphuric acid and 28 of water, 
filtering and precipitating by alcohol, as a white glutinous substance becoming 
pulverulent by repeated washings with alcohol. It may also be prepared by 
diastase ; an infusion of malt is mixed with a solution of starch, in the proportion 
of 6 or 8 of malt to 100 starch, and the liquid kept at 150° for twenty minutes. 
From being milky and viscid, it becomes nearly as fluid as water. It is then 
heated quickly to 212°, to stop the farther action of the diastase, filtered and 
precipitated by alcohol. The solution of dextrin was supposed not to be 
affected by iodine, but Jacquelain finds that dextrin is coloured purple by 
iodine, and not blue, like fecula, or that it is not colourable by iodine, 
according to the circumstances of its preparation. Thus 1 part of the 



508 AMYLACEOUS AND SACCHARINE SUBSTANCES. 

granules with 5 parts of water heated to 320° for forty-five minutes, gave a 
dextrin which was colourable purple by iodine ; while the same materials heated 
for one hour and forty-five minutes, at the same temperature, gave a dextrin 
not colourable by iodine. There can be little doubt, therefore, that there are 
two varieties of dextrin, dextrin colourable by iodine, and dextrin not colour- 
able by iodine. These varieties of dextrin also appear in the succession of 
changes which fecula undergoes under the influence of an acid. Thus a mix- 
ture of 1 part of fecula with 1 part of water and ^1^- of oxalic acid, gave when 
heated at 266° for twenty minutes, dextrin colourable purple, for one hour dex- 
trin not colourable, for two hours sugar of starch also not colourable. 

Dextrin is not fermentable by yeast, but is readily convertible by diastase 
and dilute acids into a sugar, which is fermentable. The name dextrin was 
applied to it by Biot from its effect upon a ray of polarized light passing 
through its solution, in causing the plane of polarization to deviate very con- 
siderably to the right * The composition of dextrin according to M. Payen, 
is C 12 H 10 O t0 , and of two dextrinates of lead dried at 356°,C 12 H 9 9 -f-PbO, 
and C, 2 H 9 9 -f 2PbO, so that dextrin is identical in composition with amidin, 
both when free and when in combination. Both of the dextrinates of lead re- 
tain 1 eq. of water when dried at inferior temperatures. A dextrinate of barytes, 
prepared by Payen by means of a solution of anhydrous barytes in wood spirit, 
and strongly dried between 356° and 374°, gave C^E^Og+BaOJHO. 

When dry starch is heated in an oven it becomes brown and soluble in cold 
water. It then forms British gum, which corresponds in properties with dex- 
trin. 

Diastase. — This is a remarkable substance observed by Payen and Persoz 
in grains and seeds, but only after germination, and in the tubers of the potato near 
the places from which the shoots proceed. The production of diastase is the 
principal object of the malting of grain or permitting it to germinate, and has 
an important influence upon the changes which occur in the starch of grain in 
brewing. Diastase is prepared by moistening freshly germinated barley with 
half its weight of cold water, and submitting it to pressure, by which a viscid 
liquid is obtained. This liquid is filtered and then heated to 158°, which causes 
the greater part of an azotized or albuminous matter existing in the liquid to 
be coagulated and separated. The liquid after filtration is mixed with a sufficient 
quantity of alcohol to precipitate the diastase and retain in solution the colour- 
ing matter, sugar and foreign azotized matter present. The precipitated dias- 
tase is washed with alcohol, dissolved again in water and thrown down by 
alcohol two several times, for the purpose of purifying it (An. de Chi. &c, liii, 
73.) When dried it is a white solid amorphous substance, soluble in water, 
but insipid, and not precipitated by subacetate of lead. It contains nitrogen, 
and has some analogy to gluten, but has not been obtained in a state of suf- 
ficient purity for analysis. Malted barley contains not more than 1 — 500th of 

* Memoirs by M. Biot, on Circular Polarization; Taylor's Scientific Memoirs, vol. 1 
pp. 584, 600, and Annates de Chimie et de Physique, tomes 69, p. 22, et 74, p. 401. When 
light polarized by reflection from the surface of a plate of black glass or from the surface 
of a pile of superposed plates of transparent glass reaches the eye through a disc of tour- 
malin, a solution of dextrin being interposed in a tube between the reflecting plate and 
tourmalin, the light does not disappear in those positions of the tourmalin in which light 
would be completely absorbed without the interposition of the solution of dextrin ; but 
prismatic colours are produced which follow a certain order, if the plane of polarization is 
turned from left to right. It is by the order of these colours, that a liquid is said to polar- 
ize light to the right or to the left. The solution of starch polarizes to the right and that 
of dextrin considerably more so in the same direction. While a solution of cane sugar pro- 
duces the succession of colours in an inverse order, and is said therefore to polarize to the 
left. The progress of chemical changes may thus often be observed in a solution of starch, 
the juices of plants and other organic fluids* 



GLUTEN. 509 

its weight of diastase. The solution of diastase has no action upon many- 
vegetable principles, such as sugur, gum, albumen and gluten, but has a spe- 
cific action upon starch, converting a solution of that substance first into dex- 
trin and afterwards into the sugar of starch, and such is its energy that 1 part 
of diastase will convert 2000 parts of starch into sugar. Diastase acts upon 
gelatinous starch even at 32°, but most powerfully between 140° and 150°. 
It has the remarkable property of separating the envelope from the grains of 
starch.* 

In the ordinary process of brewing, the mashing or infusing of the malt 
should be begun at 168° or 170°, the temperature at which the diastase acts 
more advantageously, by which the starch of the grain is converted into 
sweet worts. The temperature may be afterwards raised by adding water at 
185° or 195° to the mash tun; the saccharisation is generally completed in an 
hour and a half at the utmost, and the sweet worts are then run into a copper 
to be boiled and hopped, (Black on Brewing.) The sugar of the cooled worts 
is afterwards fermented by the action of another principle yeast and converted 
into carbonic acid and alcohol, as will afterwards appear. The diastase of 
1 part of malt is often made to saccharise the starch of 10 or 12 parts of un- 
malted grain, when the sweet wort is to be fermented and distilled for spirits. 

Gluten. — This substance remains when the starch of wheat flour has been 
separated by pressing the dough in water till the washings are no longer 
milky, as a gray viscid adhesive and elastic substance. It is insoluble in 
water, but is dissolved by alkalies and also by acetic acid. It contains nitro- 
gen, and when left humid in air, has a tendency to putrefy; when completely 
dry it is hard and brittle, with some resemblance to glue. Gluten forms from 
19 to 24 per cent, of good wheaten flour. According to Davy the wheat 
grown in the south of Europe is richer in gluten than that of colder climates; 
it is peculiarly suitable on that account for the manufacture of macaroni, ver- 
micelli and similar pastes, which are made by a kind of wire drawing. Glu- 
ten is one of the most nutritive of vegetable substances; when separated how- 
ever from starch and pure, gluten is scarcely digestible. 

It is to the presence of gluten that wheat flour owes its property of form- 
ing a tenacious paste with water, and also a light spongy bread. In baking 
leavened or loaf bread, the dough is mixed with a quantity of yeast, or in its 
absence with a portion of sour dough called leaven, and set aside in a warm 
place, which occasions the saccharine matter of the flour to undergo the vi- 
nous fermentation. The carbonic acid gas then evolved expands the gluten 
into vesit-les and causes the rising of the dough, which then forms a light loaf 
when heated in the oven. 

Gluten is not a pure principle; when digested in hot alcohol till every thing 
soluble is taken up, it leaves a bulky substance of a grayish colour which has 
been called vegetable albumen. The latter is soluble in water, but when the 
solution is heated the albumen coagulates and becomes insoluble; it is also 
coagulated by the stronger acitls. The true gluten, obtained by evaporating 
the alcoholic solution, retains its adhesive property and is soluble both in acids 
and alkalies. It is not precipitated from a solution in acetic acid by the ace- 
tate of lead or persulphate of iron, but abundantly by the chloride of mercury 
and infusion of gallnuts. 

Inulin. — This variety of starch was discovered by V. Rose in the root 
of the Inula Helenium, to which it owes its name. It is also found in 
various other roots, and in some lichens. It is conveniently obtained from 
the roots of the dahlia. The latter are rasped, washed with cold water and ex- 

* The name diastase was applied to it from JWtw/k/, I separate r in reference to its pro- 
perty of separating two supposed constituents of starch* 

43* 



510 SACCHARINE SUBSTANCES. 

pressed, then boiled with water, and the hot solution filtered through linen. 
This solution may be clarified by white of egg, if muddy, evaporated till a 
pellicle forms on its surface, and then allowed to cool; the inulin is deposited 
in a pulverulent form. It is collected on a filter and washed well with cold 
water. Inulin is a very fine white tasteless powder, of density 1.336, very 
soluble in boiling water, but not gelatinizing, and requiring 50 parts of cold 
water to dissolve it. Iodine makes it yellow, and insoluble in cold water. 
It is insoluble in cold alcohol, soluble in acids, which change it with the aid 
of ebullition into sugar, and more readily than ordinary starch. It is con- 
verted by nitric acid into malic and oxalic acids, without a trace of mucic acid. 
It was found by Mr. E. A. Parnel, when dried at 212°, to consist of C 24 H 21 
2 1# Two compounds which it forms with oxide of lead are thus constituted, 
C 2 4 H 2 1 ° 2 ! +5PbO, and Cjjl, gO, ? + 3PbO.* 

Lichen starch. — Several species of lichens, particularly the Cetraria Islandica 
(Iceland moss,) contain a variety of starch, closely resembling common starch. 
It gives a white and opaque jelly. It is feebly coloured by iodine, the tint pro- 
duced being between brown and green. This starch contains, according to 
the analysis of Guerin-Vary, C 10 H 11 O l9 , but this result requires confirmation. 



* SUGARS. 

Several substances are known as sugars which agree in having a sweet taste, 
but differ in other respects. Those which undergo a peculiar decomposition 
and are converted into carbonic acid and alcohol, when their, solution is mixed 
with yeast, are fermentable sugars, and form the most important class ; they 
are Cane sugar, Grape and Starch sugar, which appear to be identical, Milk 
sugar, Mushroom sugar, and the insipid sugar of Thenard, of which the two 
first-mentioned varieties are the most abundant and best understood. 



CANE SUGAR, OR ORDINARY SUGAR. 

Its formula in the crystallized state \kC 1% ti ll O tl ; in combination with 
oxide of lead, C 12 H 9 9 -f 2PbO (Peligot.) 

Loaf sugar, sugar-candy, or the purest granular muscovado may be taken to 
represent this species. It exists in many plants, but is derived in large quantity 
only from the juice of the sugar-cane, from beet-root and the maple-tree. These 
juices are rapidly evaporated with a small addition of lime, to neutralize free 
acids, being sometimes clarified first by albumen, and afford on cooling a brown 
granular sugar, from which a dark coloured syrup, molasses, separates. The 
latter contains a portion of crystallizable sugar, which may be separated from 
it by evaporation, and leaves treacle, which differs in taste from crystallizable 
sugar, and is certainly a distinct species of sugar, although highly impure. Ta 
refine sugar, it is dissolved in water, and the solution generally filtered hot 
through a bed of animal charcoal in grains like gunpowder, and about two feet 
in thickness. The colourless syrup thus obtained is evaporated in vacuo, about 
150°, in close pans heated by steam, from which the vapour is constantly with- 
drawn by an air-pump. When sufficiently concentrated, the syrup is run into 
a cooler, and agitated by an oar to promote its granulation. 

It is then transferred into moulds, which are inverted cones, having an aper- 
ture in the apex, and kept in a warm place, while the dark coloured and uncrys- 
tallizable syrup drains off; a strong syrup of pure sugar being poured on the 

* Phil. Mag. 3rd series, vol. 17, p. 126. 



CANE SUGAR. 511 

upper surface to percolate downwards and remove the last portions of the 
former. Instead of the pure syrup, moist pipe-clay was formerly placed on the 
surface of the sugar for the same purpose, and is still employed in clayed sugars. 
The loaf-sugar from these moulds is a white compact mass, composed of small 
crystals. A strong solution of it, evaporated slowly, affords large transparent 
and colourless crystals of sugar-candy, of which the form is an oblique prism of 
a square base, or a six-sided prism with dihedral summits. The density of pure 
sugar is 1.5629 (Thomson.) 

Loaf-sugar diffuses a phosphorescent light when broken in the dark. It is 
unalterable in dry air, and loses nothing but a trace of hygroscopic water when 
heated. It fuses at 356° (180° cent.) and forms a thick tenacious liquid, which 
becomes a transparent vitreous mass on cooling (barley-sugar.) The latter 
changes after a time, and rapidly when damp, into an opaque mass, which 
exhibits when broken, the crystalline facets of ordinary su^ar. Sugar is soluble 
in one-third of its weight of cold, and in all proportions of boiling water. Its 
power to crystallize is destroyed by keeping its solution for some time boiling, 
and also by the addition of 2 - th of its weight of oxalic, citric, or malic acid, 
which instantly render a viscid and boiling syrup, very fluid. Sugar dissolves 
in 80 parts of absolute alcohol at the boiling temperature, very slightly in the 
same cold, in 4 parts of alcohol of density 0.830, and is wholly insoluble in 
ether, which precipitates sugar from its solutions. Sugar is nutritive when 
accompanied with other aliments, but is incapable alone of supporting life for 
any length of time, 'in common with all organic principles destitute of nitrogen. 
A solution of sugar placed in contact with the stomach of the calf (rennet,) is 
changed entirely into lactic acid, according to the observations of Fremy. 

A solution of cane sugar is fermented by yeast, but not so readily as grape 
sugar; indeed the first action of the yeast is to convert cane sugar into grape 
sugar, which appears to be the only species of sugar that is directly fermentable 
(H. Rose;) diluted sulphuric acid with heat, and tartaric acid likewise effect the 
latter transformation of cane sugar. The first action of caustic potash in excess 
upon cane sugar, at the boiling temperature, is similar. A strong syrup mixed 
with undiluted oil of vitriol becomes hot, swells up, much charcoal is formed, and 
sulphurous and formic acids disengaged. Sugar is also decomposed by hydro- 
chloric acid, with the aid of heat, and charcoal liberated. Nitric acid converts 
it into saccharic, oxalic and carbonic acids, 100 parts of sugar yielding 67 parts 
of oxalic acid, according to Thenard. Dry chlorine has no action on dry sugar, 
but syrup absorbs chlorine slowly, and the sugar is converted, with disengage- 
ment of carbonic acid, into a brown matter, which retains some hydrochloric 
acid. Sugar dissolves carbonate of copper and verdigris, forming green sol utions, 
which are not precipitated by alkalies ; the salts, both of copper and peroxide of 
iron, cease to be precipitated by alkalies when sugar is added to them. Sugar 
also dissolves lime, barytes and oxide of lead in large quantities, and forms 
definite compounds with these bases, although in no respect an acid. Sugar is 
generally viewed as containing two atoms of water of crystallization, which can- 
not be expelled by heat, without destroying the sugar, but one or both of which 
are separated in these compounds and replaced by a metallic oxide. 

Compound of sugar and lime; C 12 H 9 9 -fCaO, HO (Peligot.) When a 
solution of sugar is digested by a moderate heat with hydrate of lime, a bitter 
alkaline solution is obtained, in which 100 parts of sugar are united with 56 of 
lime. The compound is less soluble at a high temperature, and the solution, 
when boiled, becomes a thick gelatinous mass, from which the compound sepa- 
rates as a precipitate, and may be obtained pure by washing with boiling water, 
in which it is insoluble, or by precipitation with alcohol, which retains any excess 
of sugar. The solution of this compound absorbs carbonic acid rapidly from 
the air, and acute rhombohedral crystals of hydrated carbonate of lime form in 



512 SACCHARINE SUBSTANCES. 

it. The compound of sugar and barytes is similar, according to Peligot's 
analysis, as corrected by Liebig, or C, 2 H 9 9 -f-BaO, HO. The compound of 
sugar and oxide of lead, C 12 H 9 9 -f-PbO, is prepared by dissolving oxide ot 
lead in a boiling solution of sugar; it falls as a white precipitate, which is had 
perfectly pure by washing it with boiling water, which does not dissolve it, and 
drying ; a soluble compound of sugar and oxide of lead is retained in the liquor 
which gives the precipitate. A crystalline compound of sugar and chloride of 
sodium is formed on allowing a solution of 1 part of common salt and 4 parts 
of sugar to evaporate spontaneously in air, the solution being decanted several 
times from the crystals of sugar candy, which are first deposited. The crystals 
of the compound in question have a taste at once sweet and saline, and run into 
a liquid in humid air ; their formula is 2C , 2 H 9 9 -{-NaCl, 3HO.* It is probable 
from the composition of this salt, that the usual equivalent of sugar should be 
multiplied by two, if n^)t by a higher number. 

Caramel, C 12 H 9 9 . — At a temperature a little above its point of fusion 356° 
(180° cent.,) sugar becomes brown, and at 410° or 428° (210° hr 220° cent.,) 
swells up and becomes a black porous shining mass, which is known as caramel, 
losing nothing but two atoms of water. It is obtained free from sugar, and the 
bitter products which accompany the caramel of the shops, by solution of the 
black mass in a small quantity of water, and precipitation of the caramel by 
alcohol, which retains the impurities in solution. Caramel is a black or very 
dark brown powder, neutral and insipid, soluble in water, to which it gives a 
fine colour of sepia, and not fermentable. It has the same composition as sugar 
in the compound of sugar and lead, C 12 H 9 9 (Peligot;) it precipitates salts of 
barytes and basic salts of lead. C4rape sugar furnishes the same product by 
heat. At a higher temperature, caramel loses more water, and forms an in- 
soluble matter ; when still more strongly heated it affords combustible gases, 
and leaves a bulky charcoal, difficult of incineration. 

Metacetone, C fi H 5 (Fremy,) a combustible liquid, obtained mixed with 
acetone, by distilling a mixture of 1 part of sugar with 8 parts of well pulverized 
quick-lime. The metacetone is insoluble in water, by means of which it may 
be freed from acetone. It is a colourless liquid, of an agreeable odour, boiling 
about 183.2° (84° cent.,) and miscible with alcohol and ether. It may be 
viewed as acetone, juinus one atom of water, C 5 H 6 2 — HO=C 6 H 5 0. One 
atom of anhydrous sugar contains the elements of: 

1 atom of acetone. . . C 3 H 3 O 

1 atom of metacetone. . . C 6 H 5 O 

3 atoms of carbonic acid. . C 3 6 

1 atom of water. . HO 



C l2 H 9 O, 



Saccharic acid, C 12 H 5 O xl -f 5HO=C I2 H l0 O l6 (Thaulow.) This acid 
was designated oxalhydric acid by Guerin-Varry; it is a product of the action 
of dilute nitric acid on either cane or grape sugar. It is procured by dissolving 
1 part of sugar or of gum in two parts of nitric acid diluted with 10 of water, 
and heating' so long as chemical action is manifested. The acid liquid is then 
neutralized with carbonate of lime, and the neutral acetate of lead added to it. 
The saccharate of lead which falls is decomposed by sulphuretted hydrogen, 
and the free acid half neutralized by carbonate of potash, and crystallized as 
the acid saccharate of potash. The last salt is decolorized by charcoal, con- 



* Peligot; Recherches sur la nature et les proprietes chimiques des sucres, An. de Ch« 
&c, t. 67, p. 113 ; et sur la composition du saccharate de plomb. lb. t. 73, p. 103. 



GRAPE SUGAR. 513 

verted again into a salt of lead, and the acid liberated by sulphuretted hydro- 
gen. Saccharic acid when concentrated is syrupy, colourless, sharply acid, 
and deposites colourless crystals, after long repose. It is soluble in alcohol 
in all proportions, and slightly in either. It does not precipitate salts of 
barytes or lime, but produces white flocculent precipitates in barytes-water 
and lime-water, which are soluble in an excess of acid. 

This acid is remarkable for the variety of compounds it forms with bases. 
It is supposed to be pentabasic, and to form 5 series of salts, according as 1 
atom, 2, 3, 4, or the whole 5 atoms of water are replaced by metallic oxides; 
but it is possibly only tribasic, although capable of forming a subsalt with 
oxide o*flead. Of the following salts, the composition is known. 

Hydrated saccharic acid . . C l2 H s 11 ~\-5B.O 
Acid saccharate of potash . . C^H.O^ -f 4 jjq 

Saccharate of ammonia . . C ia H 5 0! t -f- ^jjq 

First saccharate of lead . . C^H.Oj l+gjjQ 

Saccharate of zinc . . . Cj 2 HjO n -f ojjq 

Second saccharate of lead . . C 2 2 H 5 x j -f ouq 
Third saccharate of lead . . C , 51150! t -}-5PbO 

It is remarkable that hydrated saccharic acid contains the elements of 2 
atoms of mucic acid; C 12 H , ,0, e ==2(C 6 H 5 3 ;) a substance produced by 
the same mode of oxidation of milk sugar.* 



GRAPE SUGAR. 

Syn. Starch sugar, diabetic sugar, the sugar of fruits, glucose (Dumas.) 
Thelformula of crystallized grape sugar is C la H 14 14 , but at 212° it fuses 
and loses 2 atoms of water. This is the sweet principle of raisins, figs, and 
of most acid fruits; it exists also in honey, and is the sugar of diabetic urine. 
It is also a product of the decomposition or transformation of several other 
substances, as of cane sugar, starch, lignin and milk sugar, when treated with 
dilute acids. Grape sugar is not so soluble in cold water as cane sugar, and 
about 2i times less sweet. 

It is obtained from the grape, by neutralizing the expressed juice with 
chalk, clarifying with white of egg, evaporating and setting aside to crystallize. 
From the urine of diabetes, by evaporating the latter to dryness in a water- 
bath, washing the dark crystalline mass on a filter with cold alcohol, and sub- 
mitting the white residue, dissolved in water, to repeated crystallizations. 
But this sugar is most largely prepared from starch, and, indeed, forms a con- 
siderable article of commerce. One part of potato starch is boiled with from 
l-100th to 1— 10th of its weight of sulphuric acid and four parts of water, for 
thirty-six or forty hours, the water being replaced as it evaporates. The so- 
lution ceases to be gelatinous, and passes first into dextrin and then into sugar. 
Under some pressure, and at a higher temperature, the change is effected more 
quickly and by means of a less quantity of acid. A small quantity of oxalic 



* Thaulow, sur l'Acide Saccharique, An. de Chiraie, &,c. Ixix, 52. 



514 SACCHARINE SUBSTANCES. 

acid -ji- may be substituted with advantage in this process instead of the sul- 
phuric acid. The acid is afterwards neutralized with chalk, the solution fil- 
tered from the insoluble salt of lime, and evaporated to a syrup, which solidi- 
fies as a crystalline sugar. Starch is also converted into sugar by means of 
diastase. Eight parts of ground malt are infused at 158° (70° centigrade) in 
400 parts of water, and then mixed with 100 parts of starch, which soon dis- 
solves, and by continued digestion at the same temperature is entirely changed 
into sugar. By calculation, 100 parts of fecula, combining with the elements 
of four atoms of water, should produce 122.03 parts of crystallized grape 
sugar; De Saussure obtained 110 parts, and Brunner from 104 to 106 parts. 
In the transformation of starch into sugar, a variable quality of mahnite is 
always formed at the same time, according to the observations of Fremy. 

To prepare grape sugar from lignin or woody fibre, 12 parts of wood shavings 
or shreds of paper are gradually mixed with 5 parts of oil of vitriol diluted with 

1 part of water, care being taken to avoid any rise of temperature ; after 
twenty-four hours' digestion, the pitchy mass is dissolved in much water, and 
boiled for ten hours, and the acid afterwards separated as in the former process 
for sugar from starch. 

Grape sugar does not crystallize so distinctly as cane sugar, but is obtained 
from its alcoholic solution in square tables or cubes, which are hard and trans- 
parent. It is soluble in U parts of cold water, and in all proportions of hot 
water. It dissolves less rapidly than cane sugar, and gives a more fluid syrup. 
In alcohol, at a low temperature, it is very sparingly soluble, but at 77° (25° 
cent.) it is soluble in 8 parts of alcohol of 85 per cent, and in 20 parts of 
absolute alcohol. It fuses with loss of water at 212°, and is converted into 
carmel when not heated above 284° (140° cent.) 

The chemical action of acids and alkalies upon grape and cane sugars are 
essentially different. Grape sugar dissolves in concentrated sulphuric acid, 
colouring it slightly yellow or brown, and forms a compound with it, the sul- 
phosaccharic acid, while cane sugar is carbonised in the same circumstances. 
On the other hand, alkalies which do not alter the colour of cane sugar, even at 
the boiling point, provided they are dilute, convert grape sugar with heat, into 
a brown or brownish black substance. The compounds of grape sugar with 
barytes, lime and oxide of lead are formed with difficulty, while a crystalline 
compound with chloride of sodium is easily prepared. 

Compounds of grape sugar. — According to the recent analyses of Erdmann 
and Lehman, the compound of grape sugar and chloride of sodium contains 2 
atoms of water, which it loses at 212°. Its formula in the crystallized state is 

2 (C 12 H l2 12 )-f NaCl,2HO. This compound loses 3 atoms of water at 320° 
(160° cent.,) according to Peligot, but then its sugar is modified. The com- 
pound of grape sugar and oxide of lead, precipitated on mixing the sugar 
with acetate»oflead containing ammonia (page 412,) consists, according to the 
analysis of Peligot, as corrected by Liebig, of C t «Hj 1 1 x -r-3PbO, or in its for- 
mation 3 atoms of water are replaced by 3 atoms of oxide of lead. The solu- 
tions of lime and barytes in grape sugar become brown, when heated. 

Sulpho saccharic acid was formed by Peligot, by fusing 1 part of crystallized 
starch sugar by the heat of a water-bath, and then mixing the mass in small 
portions with concentrated sulphuric acid. The compound is then dissolved in 
water, and saturated with carbonate of barytes, which precipitates sulphuric 
acid, while the sulphosaccharate of barytes remains in solution. The acid 
liberated from combination is a sweet liquid, feebly acid, which forms soluble 
salts with almost all bases. The solution of sulphosaccharic acid is easily de- 
composed by evaporation, and resolved into sugar and sulphuric acid, .which 
then precipitates barytes. Its composition has not been determined with cer- 
tainty. 



SUGAR OF MILK. 515 

Sacchulmine is a substance obtained in brown, brilliant, crystalline plates, 
by boiling cane sugar for a very long time in very dilute sulphuric, hydrochlo- 
ric or nitric acid ; it is insoluble in ammonia. Sacchulmic acid, of which the 
formula is C 30 H l5 O 15 , according to Malaguti, is formed at the same time, 
and many may be separated by ammonia, in which it is soluble, from sacchul- 
mine. 

Glucic acid is formed when a saturated solution of lime or barytes, in grape 
sugar, is left to itself for some weeks (Peligot.) The probable formula of 
anhydrous glucic acid is C 24 H 15 O l5 , or it is formed from grape sugar 
by the loss of the elements of water. Melassic acid is produced by the 
simultaneous action of alkalies and heat upon grape sugar. With the con- 
currence of air and a high temperature, alkalies convert sugar into formic 
and sacchulmic acids. 



SUGAR OF MILK OR LACTINE. 

Its formula, in the crystallized state, is C 24 H 24 24 , orC 2 ^HjgO^-f 5HO; 
by a heat of 248° (120° cent.) it loses 2 atoms, and by 302° (150°~ cent.) 5 
atoms of water (Berzelius.) Sugar of milk is obtained by evaporating the 
whey of milk to crystallization, and purifying the first product by animal char- 
coal and a second crystallization. It forms white quadrangular prisms, termi- 
nated by four-sided pyramids, which are semi-transparent, and have the density 
1.543. They are soluble in 5 or 6 parts of cold water, and in 2.1 parts of boil- 
ing water, without forming a syrup. The sweet taste of the crystals is very 
feeble when they are applied directly to the tongue, but that of their solution 
is much more distinct. Sugar of milk is unalterable in air, loses nothing at 
212°, and is insoluble in alcohol and ether. Its solution dissolves hydrate of 
lime, and is converted by dilute mineral acids into grape sugar, assuming then 
the elements of 2 atoms of water. When milk is exposed to a temperature 
of 95° to 104° (35° to 40° cent.,) it undergoes the vinous fermentation, and is 
found afterwards to contain alcohol, while its sugar disappears, but the latter 
is converted first into grape sugar, probably under the influence of the free 
acid which is formed and curdles the milk. Milk sugar forms two compounds 
with oxide of lead, of which the formulas are C 24 H 19 19 -fSPbO, and C 24 
H, 9 , 9 + lOPbO (Berzelius.) 

Mucic acid, C, 2 H 8 14 -(-2HO (Berzelius, Malaguti,) is produced by the 
action of 4 parts of nitric acid, of density 1.42, diluted with 1 part of water, 
aided by heat, on 1 part of sugar of milk; a portion of the latter always pass- 
ing at the same time into oxalic acid. It is also formed by the action of nitric 
acid on gum. Mucic acid is deposited on cooling, a« a white crystalline pow- 
der, of which the taste is feebly acid, soluble in 6 parts of boiling water, and 
insoluble in alcohol. It is a bibasic acid, of which the salts of an alkaline base 
are soluble in water, and those which contain an alkaline earth, or the oxide of 
a metal proper, are insoluble. Mucic ether, 2C 4 HyO-r-C, 2 H 3 0, *■> is solid 
and crystallizes in quadrilateral colourless prisms. Modified mucic acid is 
produced by boiling a concentrated solution of mucic acid, or evaporating it by 
heat. Its acid powers are more distinct than those of mucic acid, and it is 
also distinguishable from the latter by the physical properties of its salts. 
The modified acid is either isomeric with mucic acid, or contains the elements 
of an atom of water in addition (Malaguti.) Pyromucic acid, C 10 H 3 O 5 4- 
HO, is produced in the dry distillation of mucic acid, by the separation of 6 
atoms of water, and 2 atoms of carbonic acid; 

C l2 H 8 14 +2HO = C 10 H 3 O, and6HOand2C0 2 . 



516 SUGAR. 

It forms elongated, white and brilliant plates, which fuse at 266° (130° cent.,) 
and volatilize without residue at a temperature a little higher. It is soluble in 
26 parts of cold and in 4 parts of boiling water, dissolves easily in alcohol, 
and is not altered by nitric acid. It forms a class of mono-basic salts, including 
pyromucic ether C^HjO+CjoH^O,., which is solid. Pyromucic ether ab- 
sorbs 4 atoms of chlorine gas and becomes liquid, without the liberation of any 
hydrochloric acid, forming a compound, which Malaguti names chloropyro- 
mucic ether, C 14 H 8 C1 4 6 ; but of which the true constitution is uncertain. 



MUSHROOM SUGAR. 

This sugar, of which the formula is C T2 H I3 T 3 , according to an analysis 
by MM. Liebig and Pelouze, was obtained by M. Wiggers by treating the 
tincture of the ergot of rye by water. It crystallizes, and is soluble in water 
and alcohol, but not in ether. Mushroom sugar is also fermentable by yeast, 
and diffuses the odour of caramel when carbonized by a high temperature. 
This sugar does not throw down sub-oxide of copper from a boiling solution 
of the acetate, the only property by which this sugar is distinguished from the 
ordinary species. 



INSIPID SUGAR. 

A species of sugar was obtained by Thenard, from the urine of diabetes in- 
sipidus, and subsequently by Bouchardat from the same source, which was 
insipid, or only faintly sweet. It was fermentable by yeast, and was con- 
verted by dilute sulphuric acid into the sugar of grapes.* 



LIQUORICE SUGAR. 

The inspissated juice of the root of the Glycyrrhiza glabra, contains a spe- 
cies of unfermentable sugar, which is obtained by clarifying the juice with al- 
bumen, and precipitating the sugar with sulphuric acid, washing the precipi- 
tate with water, dissolving it in alcohol, which leaves undissolved some albu- 
men; and then decomposing the sulphate of liquorice sugar by carbonate of 
potash. After evaporation, the sugar remains as a yellow translucent mass, 
cracked in all directions, and easily detached from the vessel in which it was 
evaporated. Liquorice sugar possesses the property of forming soluble or 
sparingly soluble compounds with both the mineral and vegetable acids. It 
also combines w r ith bases. 



MANNA SUGAR, OR MANNITE. 

C 6 H 7 6 ,. according to the analyses of Oppermann and of Liebig. Manna 
is in oblong globules or masses, of a yellowish-white colour, and is an exuda- 
tion from various trees, principally the Fraxinus ornus, a species of ash, and 
the Eucalyptus mannifera* of New South Wales. It exists also in the juices 

* Thenard, Traite de Chimie, IV. 351. 

t [Professor F. W. Johnson, has ascertained that this species of Eucalyptus does not afford 
manna, but a new species of sugar, composed in its crystalline state of C 24 H 28 28 ; but 
losing by heat 7H0, becoming C 24 H 21 21 . It is not as sweet as grape sugar. Proceed. 
Acad. Nat. Scien. Phila. Jan. and Feb. 1843, and Lond. Atheneum. R. B.] 



LIGNIN. 517 

exuded by many cherry and plum trees, in various kinds of mushrooms, and 
in some roots, such as that of celery. It is composed chiefly of manna sugar, 
which may be prepared by dissolving the manna of the shops in boiling alco- 
hol, and allowing the solution to cool, and is obtained perfectly pure by re- 
peated crystallizations. Mannite crystallizes in slender, colourless four-sided 
prisms, of a silky lustre. It has a slightly sweet taste, and is very soluble in 
water; its solution is not fermentable. Mannite is anhydrous, and may be 
fused by heat without loss of weight. Its solution dissolves oxide of lead. 
Nitric acid converts mannite into oxalic and saccharic acids, and not into mucic 
acid. 

Mannite is also one of the products of the viscous fermentation of cane and 
grape sugar, which will be afterwards described. 



GUM. 

Its formula is C J2 H 11 11 ; it loses an atom of water at 266° (130° cent.*) 
but is then essentially altered. Gum is a principle of constant occurrence in 
the juices of plants, and exuding from the bark of trees, collects into drops, 
which are distinguishable from resin by being soluble in water and insoluble 
in alcohol. All the varieties of gum may be referred to two species, of which 
gum-arabic (the produce of the acacia vera,) and gum-tragacanth are the 
types. The first is slowly soluble in cold water, the last does not dissolve in 
water, but swells up into a mucilaginous mass, which, when boiled, gradually 
acquires the appearance of ordinary gum. The solution of gum, known as 
mucilage, is a thick, adhesive, insipid liquid, from which the gum is thrown 
down by alcohol. Gum is precipitated by sub-acetate of lead, as a white 
mass, insoluble in water. It is destroyed by the strong acids; nitric acid con- 
verts it into mucic acid. 



LIGNIN. 

The formula of lignin, dried between 300° and 350° is C 12 H 8 3 (Prout.) 
The basis of woody fibre is aptly so named. It constitutes about 95 per cent* 
of baked wood, and is the most durable product of vegetation. Pure lignin is 
obtained by treating the sawings of wood, paper, or the fibre of lint and cotton, 
successively with ether, alcohol, water, a diluted acid, and a diluted caustic 
alkali, to dissolve all the matters soluble in these menstrua. Wood contains 
in its vessels the various constituents of the sap, of which the colouring prin- 
ciple attaches itself to the lignin on evaporation, by a chemical affinity, such 
as we avail ourselves of in dyeing vegetable fibre. It has been observed by 
Hartig that the pores of wood also contain a certain quantity of starch, in 
spherical grains of a gray colour, of which from one-fourth to one-fifth of the 
weight of the wood may be obtained by mechanical means. The lignin of 
wood consists according to M. Payen, of two organic principles, which he 
has succeeded in separating; one is the primitive tissue, composing the vessels 
of the wood, which is isomeric with starch, C 12 H l0 O 10 , and is named by him 
cellulose; the other fills the cells, and constitutes the true ligneous matter. M. 
Payen obtained cellulose by the action on the sawings of beech-wood of several 
times its weight of the most concentrated nitric acid, which leaves that princi- 
ple, while it dissolves the lignin. Cellulose is dissolved by concentrated sul- 
phuric acid, without blackening, and is then converted into dextrin. The true 
lignin of lint, hemp, straw, and linen cloth, was found by Payen to be C 35 
H 24 O 20 . Oak-wood, by the analysis of Gay*Lussac and Thenard, is C 36 
44 



518 ETHYL. 

H 22 22 . Hemp, straw, etc., mixed cautiously with concentrated sulphuric 
acid, so as to prevent elevation of temperature, form, besides dextrin, a lignin^ 
sulphuric acid, analogous to benzo-sulphuric acid, which forms soluble salts 
with barytes and oxide of lead. The dextrin formed when lignin is dissolved 
in sulphuric acid, is converted by dilution and boiling, into starch sugar. 
Sawdust, gum and starch dissolve in the most highly concentrated nitric acid 
(page 219,) without decomposition of the acid, and if immediately diluted 
with water, give a white pulverulent neutral substance, insoluble in water, 
which contains the elements of nitric acid and is highly combustible (Robi- 
quet.) 

Lignin combines with several neutral salts, such as chloride of mercury, sul- 
phate of copper, and acetate of iron, with all of which, particularly the first, 
wood is impregnated, in order to preserve it from dry rot, a species of decay 
to which wood is subject. The wood loses all its cohesion, and becomes fria- 
ble when affected by dry rot, and fungi generally appear upon it, but the first 
destructive change is probably of a chemical kind allied to the action of fermen- 
tation. Dr. Boucherie has found that wood may be completely charged with so- 
lutions of salts for its preservation, by aspiration from the roots or base of the 
trunk of the tree, shortly after it is cut down, and has made many other new 
observations^ on the subject.* 

Suberic acid, HO-j-C 8 H 6 3 , is formed among other products by the action 
of moderately concentrated nitric acid, with heat, upon barks, but more parti- 
cularly cork. It is produced, likewise, from stearic and oleic acids in the same 
manner. Suberic acid is deposited from a saturated hot solution in water, as 
a white earthy powder, slightly sour, which is fusible and distils over like an 
oil, fixes on cooling, and is crystalline. It is soluble in alcohol and ether. 



SECTION II. 

PRODUCTS OF THE FERMENTATION OF SUGAR. 

ETHYL SERIES OP COMPOUNDS. 

Ethyl, C 4 H 5 =E, a hypothetical radical existing in ether and its compounds; 
ether being the oxide of ethyl, and alcohol the hydrated oxide of ethyl. Ethyl 
has not been isolated. 

HYDRATED OXIDE OF ETHYL, OR ALCOHOL. 

Its formula is C 4 H 5 0-f HO=EO-f HO. Alcohol can be obtained only in one 
way, namely by the fermentation of sugar, and perhaps immediately from grape 
or starch sugar only. This fermentation is determined by the addition of yeast 
to a solution of sugar kept between 70° and 80°, when a new distribution of 
the elements of the latter takes place, so as to form alcohol and carbonic acid ; 
one atom of starch sugar C 12 H 1; 
hoi 2 (C 4 H 5 0-f-H0,) and four atoms of carbonic acid 4C0 2 . 

* Annates de Cljim.etc. lxxiv. 113. 



ALCOHOL. 519 

Two atoms of alcohol . . . C 8 H 12 O^ 
Four atoms of carbonic acid . C 4 8 



One atom of starch sugar . . C 13 H l2 12 

/ 

The juices of all plants which naturally contain sugar, possess, likewise, a sub- 
stance which by exposure to air, becomes a ferment and converts their sugar 
into alcohol and carbonic acid. Hence all saccharine vegetable juices, such as 
that of the grape, of sugar-cane, and of beet root, run quickly into fermentation 
after expression. 

Alcohol is obtained by distillation from all liquids which have undergone the 
vinous fermentation, but diluted with a large quantity of water. The density 
of the distilled liquid diminishes with the proportion of alcohol, and tables have 
been constructed by which from its density the per-centage of alcohol in the 
liquid may be ascertained. Ordinary spirits have a specific gravity from 0.910 
to 0.915, which corresponds with from 50 to 52 per cent, of alcohol. The 
same distilled afford a spirit of density from 0.890 to 0.880, at 60°, known as 
spirits of wine, containing from 62 to 67 per cent, of alcohol; which again may 
be brought, by a second distillation, to from 0.843 to 0.835, known as rectified 
.spirits, and these contain from 82 to 85 per cent, of alcohol.* To obtain alco- 
hol free from water, or absolute alcohol, rectified spirits may be poured into a 
retort over their weight of anhydrous lime, in fine powder, either fresh quick- 
lime finely pulverized, or better lime that has been slaked and afterwards heated 
recently to redness, allowed to digest together for twenty-four hours, and the 
spirit afterwards slowly distilled by the heat of a water-bath. It then has a 
specific gravity of 0.7947 at 59° (15° cent.,) and from 0.792 to 0.791 at 68^ 
(20° cent.) The proof spirits of the excise upon which the duty per gallon is 
levied in this country, is of density 0.918633 ; and by the expression that a 
spirit is any number, say ten, over proof, is meant that 100 gallons of the spirit 
would stand the addition of ten gallons of water to reduce it to proof strength, 
or it would form 110 gallons of proof spirit; while ten under proof, means that 
ten gallons of water must be taken from 100 gallons of the spirit to raise it to 
proof, or that 100 gallons of it contain only 90 gallons of proof spirit. The 
proof spirit of the pharmacopeia (spirit us termior) is directed to be of sp. gr. 
0.930. When obtained from grain, alcohol always contains a small quantity 
of a particular oil, from which it is most easily purified on the small scale by 
distilling it from caustic potash, or filtering it, when in a large quantity, through 
a bed of recently prepared wood charcoal, roughly pounded. 

Alcohol has never been frozen. By evaporating the compound of solid car- 
bonic acid and ether, in the vacuum of an air-pump, Dr. Mitchell has produced 
the greatest depression of temperature hitherto attained. Alcohol of specific 
gravity 0.798, was observed by him to become oily and adhesive at — 130°; 
by a greater cold it became still thicker, and at — 146° flowed like metal wax. 
Alcohol of 0.820 froze easily; ether underwent no change by the lowest of 
these temperatures.! 

Alcohol boils at 173° (barometer 29.5 inches,) and at higher temperatures, in 
proportion as it is diluted with water. It is remarkable, however, that the 
boiling point of a mixture of alcohol and water rises with the quantity of water 
to a certain point ; alcohol of 96 to 99 per cent, boiling at a somewhat lower 
temperature than absolute acohol. In consequence of this, alcohol of density 
0.800 is increased in strength by boiling it: and hence also, in the preparation 



* Table of the Density of Alcohol, by M. Lowitz, see Appendix. 

f Liebig's Annalen, vol. 37, p. 354: from Silliman's American Journal of Science. 



520 ETHYL. 

\ 

of absolute alcohol, the first portions contain always a little more water than 
those which follow. Alcohol has an agreeable penetrating odour, and is the 
intoxicating principle of all spirituous liquors. The density of its vapour, 
according to Gay-Lussac, is 1613, referred to air as 1000; it contains eight 
volumes of carbon vapour, twelve volumes of hydrogen, and two volumes of 
oxygen condensed into four volumes, its combining measure, which gives the 
theoretical density 1601 . Alcohol is highly combustible, and burns with a flame 
that is nearly colourless and free from smoke ; the only products of its perfect 
combustion are water and carbonic acid. 

Alcohol has a great attraction for water, which when anhydrous, alcohol 
attracts rapidly from the air. It also withdraws water from animal substances, 
and thus preserves them. When mixed with water, a very sensible evolution 
of heat occurs, and always a diminution of bulk and increase of density, when 
water and absolute alcohol are mixed in any proportions, although on adding 
water to alcohol, already considerably diluted, an apparent expansion may be 
observed. The greatest contraction occurs on mixing 1 atom of alcohol with 6 
atoms of water, when a definite hydrate is certainly formed; 100 volumes of 
this mixture contain 53.939 volumes of alcohol, and 49.836 volumes of water; 
consequently, 103.775 volumes are reduced to 100; its densitv is 0.927 at 
59°.* 

Alcohol dissolves most of the gases, and several of them in a larger propor- 
tion than water, such as oxygen, nitrous oxide, carbonic acid, and phosphuretted 
hydrogen. It dissolves the hydrates of potash and soda, ammonia, the alkaline 
sulphurets, likewise all the deliquescent inorganic salts, except carbonate of 
potash, but none of the salts which are insoluble or sparingly soluble in water, 
nor efflorescent salts. It dissolves many vegetable principles, such as sugar, 
resins, essential oils, soap, castor oil, ethers, alkalies, most acids, &c. It does 
not dissolve the fats and fixed oils. Alcohol forms crystalline compounds with 
several of the salts it dissolves, particularly chloride of calcium, (CaCl-f 2C 4 H 6 
2 ,) nitrates of lime and magnesia, chloride of zinc, and chloride of manganese. 
These compounds are named alcoates, and correspond with hydrates, but are 
much less stable. Many solutions made by alcohol, or tinctures are used in 
medicine. 

Absolute alcohol dissolves l-240th of phosphorus, and l-200th of sulphur. 
It is decomposed by potassium or sodium, with the evolution of hydrogen gas, 
and a crystallizable compound is formed of the remaining elements of the 
alcohol with the metal, or perhaps of ether with the oxide of the metal. This 
substance is decomposed by water. Oxygen acids decompose alcohol, as 
they do a hydrated metallic oxide, uniting directly with the ether it contains, 
and forming acid salts of that base; while a hydracid acts upon the ether of 
the alcohol as it does upon a metallic oxide, forming water, and a haloid com- 
pound of the radical of the hydracid with ethyl. 



OXIDE OF ETHYL, OR ETHER. 

Formula: C 4 H 5 0=EO; distinguished also as sulphuric ether, from the 
mode of preparing it. This liquid is the product of a remarkable decomposi- 
tion of alcohol by sulphuric, phosphoric and arsenic acids, and is also formed 
by the action upon alcohol of the fluoride of boron, the chloride of zinc, the 
chloride of tin, and some other chlorides. All these agents have a great affi- 
nity for water, and might be supposed to convert alcohol into ether by simply 
combining with the water which the former is supposed to contain, but the 

■' Rudberg, Annates de Chim. etc. xlviii, 33. 



ETHER. 521 

close examination which the process of etherification has received from che- 
mists, proves that its rationale is by no means so simple. Reserving the 
theory of ether till that of sulpho-vinic acid is considered, I shall at present 
describe the process for ether. 

Ether is evolved when alcohol and oil of vitriol are heated together, and 
may be obtained by mixing and distilling in a glass retort equal weights of 
these materials, due attention being paid to the condensation of the product, 
which is volatile, by keeping the receiver very cold. But as the power of the 
acid to decompose alcohol is not exhausted in this process, it is found advan- 
tageous to make additions of alcohol to the remaining acid, or to introduce the 
latter in a continued stream. The following is a continuous process for ether, 
first proposed by M. Mitscherlich, as it is given by M. Liebig. Alcohol is 
employed of density 0.822, or of 90 per cent, which may be obtained by 
digesting proof spirits upon an equal weight of well dried carbonate of potash 
(free from caustic potash,) when two liquids are formed, the upper alcohol of 
the strength mentioned, which may be drawn off for use, and the lower, a 
solution of carbonate of potash m water. Five parts, by weight, of this alco- 
hol are mixed with nine parts of oil of vitriol, in a copper or cast iron vessel, 
surrounded by cold water, and the mixture afterwards introduced into a tubu- 
lated glass retort, which the mixture should fill one half, or even a little more. 
The distillation is best conducted by the heat of a sand-pot, in which the 
retort should not be deeply sunk, and commences at a gentle heat; when the 
temperature increases too briskly, the fire should be withdrawn. A glass tube 
is fixed by a cork in the tubulure of the retort, of which the extremity within 
the retort is drawn out into a point, having 'an opening about one line in dia- 
meter, and dips one inch in the liquid. Without the retort, the same tube is 
bent at a right angle, and may extend horizontally for two or three feet; it 
communicates with a reservoir of alcohol by means of a metallic tube and 
stop-cock, by which the flow of the alcohol is regulated. The latter should 
be supplied so as to keep the liquid in the retort at its original level, at which 
a mark should be placed for that purpose. To condense the ether which dis- 
tils over, the beak of the retort is connected with Liebig's tube condenser, 
(page 64) charged with the coldest water. A leaden alembic is used when 
ether is prepared on a large scale. It is said that when the operation is well 
directed, nothing is formed but ether and water: the same sulphuric acid may 
also be used indefinitely for the preparation of ether without sensibly dimi- 
nishing, the ether and water into which the alcohol is resolved, coming off 
entirely, and leaving none of its elements with the acid. 

To obtain the ether perfectly free from alcohol and other impurities, the 
crude product may be mixed with some milk of lime and an equal volume of 
water, the lighter liquid drawn off, and allowed to digest for several days 
upon chloride of calcium, or quicklime; and finally be rectified from the same 
substances. The last product has a specific gravity between 0.720 and 0.725. 

Ether is a light, transparent, highly limpid, fragrant and volatile liquid, 
having a sharp aromatic taste, and which when swallowed or inhaled in the 
form of vapour, acts as a powerful stimulant. Its density is 0.715 at 68°, and 
0.724 at 54°, by Gay-Lussac's observations. It boils between 96° and 98° 
(26°. 5 cent. Gay-Lussac;) evaporates , rapidly at ordinary temperatures, and 
produces great cold by its evaporation. It is very combustible, and a mixture 
of its vapour with air or oxygen is explosive in a high degree; hence it must 
always be distilled with caution. Ether, unlike alcohol, burns with a white 
flame; it is converted into water and carbonic acid. When a spiral coil of 
of platinum wire, heated red-hot, is suspended in the vapour of ether, the latter 
burns without flame, and produces a very acrid vapour, which when con- 
densed has been found to contain acetic, formic and aldehvdic acids. When 

44* 



522 ETHYL. 

transmitted through a red-hot tube, ether is decomposed into aldehyde, de- 
fiant gas, and the gas of marshes. 

Ether mixes with alcohol in all proportions, but may. be separated com- 
pletely from the latter by agitation with* twice its bulk of water, which takes 
up the alcohol while the ether floats on its surface. One part of ether dis- 
solves in 10 parts of water, while 36 parts of ether dissolve 1 of water. Its 
solvent powers are much less extensive than those of alcohol. Ether dis- 
solves l-80th of sulphur, and l-37th of phosphorus, and also iodine and 
bromine in large quantity, but is soon decomposed by them. It dissolves also 
a considerable number of chlorides, such as that of mercury, of zinc, and gold. 
Ether dissolves also several organic acids, such as the acetic, gallic, benzoic, 
oleic and stearic acids, also the essential oils, fats, wax, and certain resins. 
Certain vegetable bases are also soluble in ether, while others are not. 

The vapour of ether is very heavy, its density being 2586 (Gay-Lussac;) 
it contains 8 volumes of carbon vapour, 10 volumes of hydrogen, and 1 volume 
of oxygen, condensed into 2 volumes, which form its combining measure, 
and give as its theoretical density 2583. 

Ether left a long time in contact with water, combines with it and forms 
alcohol. It combines with acids, and forms both neutral and acid salts; the 
first class of salts are the compound ethers, and the last bear the name of 
vinic acids. 



CHLORIDE OF ETHYL, OR HYDROCHLORIC ETHER. 

Its formula is C 4 H 5 C1 = EC1. To prepare this ether, alcohol is saturated 
with hydrochloric acid gas, and the solution distilled by a water-bath heat; 
the product is conducted into a bottle containing some water and surrounded 
by water at the temperature of 70° or 80°, and thence into another receiver 
surrounded by ice. To free it from water and alcohol, the product is digested 
with chloride of calcium in a bottle surrounded by ice. The liquid is decanted, 
after twenty-four hours, into phials, with well ground stoppers, which are 
kept inverted. 

Hydrochloric ether is a highly volatile liquid, boiling at 52°, of a pene- 
trating aromatic and slightly alliaceous odour. Its density is 0.874 at 41°, it 
is neutral to test paper, dissolves in twenty-four parts of water, and gives a 
solution that is not precipitated by nitrate of silver. When treated with 
chlorine, it gives hydrochloric acid, and a series of compounds to which 
reference has already been made (page 491.) 

Bromide of ethyl, C 4 H 5 Br = EBr, was discovered by Serullas, and is formed 
by distilling a mixture of one part of bromine, 4 of alcohol, and l-8th of phos- 
phorus. It is a colourless and very volatile liquid, denser than water. 

Iodide of ethyl, C 4 H 5 I = EI, may be obtained by distilling alcohol, satu- 
rated with hydriodic acid gas. It is a colourless liquid, of density 1.9206, 
which boils at 161°. (71°. 5 cent.) 

Sulphur et of ethyl, C 4 H 5 S = ES, is formed by transmitting the vapour of 
hydrochloric ether through the proto-sulphuret of potassium; chloride of po- 
tassium precipitates, the sulphuret of ethyl is dissolved by the liquid, or dis- 
tils over if the latter is kept warm. It is a colourless liquid, of a disagreeable 
alliaceous odour, boiling at 163°.4 (73° cent.,) and of which the density is 
0.825 at 68°.* 

* Regnault, An. de Ch. etc. Ixxi, 387. 



MERCAPTAN, 523 



HYDROSULPHURET OF THE SULPHURET OF ETHYL, OR MERCAPTAN, 

Its formula is C 4 H 5 S+HS=ES + HS; or it is alcohol of which the oxy- 
gen is replaced by sulphur. This curious compound, of which we owe the 
discovery to Zeise, may be prepared like the preceding compound, by trans- 
mitting the vapour of hydrochloric ether through a strong solution of potash, 
previously saturated with sulphuretted hydrogen gas, or hydrosulphuret of 
sulphuret of potassium, KS-f HS; but a preferable process is to distil a strong 
solution of the sulphate of oxide of ethyl and lime, of density 1.28, mixed 
with a solution of potash of the same density, previously saturated with sul- 
phuretted hydrogen gas. 

KS,SH and (EO + CaO-f-2S0 3 )=ES + HS and KO-f S0 3 and CaO-f S0 3 . 

The product must be received in a cool receiver. It contains an excess of 
sulphuretted hydrogen, alcohol, and water, from which it may be purified by 
submitting it to a second distillation from a small quantity of red oxide of mer- 
cury, and digesting it afterwards with chloride of calcium. 

Mercaptan is a colourless liquid, highly fluid, like ether, having a most 
penetrating and insupportable garlic odour; its boiling point is about 100°, 
according to my own observation, and the density is said to be 0.835 at 70°, 
and 0.842 at 59°. It is miscible with alcohol and ether, but not with water, 
in which it is very slightly soluble. The sulphuretted hydrogen of mercaptan 
acts powerfully on metallic oxides, water being formed, and a sulphuret of the 
metal, which last remains in combination with the sulphuret of ethyl, thus 
forming a class of sulphur salts. The oxide of mercury is instantly converted 
by mercaptan into a compound of this class, C 4 H 5 S-f-HgS,* the mercaptide 
of mercury, which is a white crystalline mass, soft to the touch, without 
odour, insoluble in water, and fusible, like wax, by 185° (85° cent.) This 
mercaptide, when distilled, leaves cinnabar, and affords a volatile liquid, which 
has not been examined. The oxide of gold is also strongly acted on by mer- 
captan, but other metallic oxides are less affected in proportion as they ap- 
proach to alkaline bases. Thus the hydrates of potash and soda have no 
sensible action on mercaptan. 

By contact with nitric acid, mercaptan is converted, by a gentle heat, into 
a new acid, which contains sulphuret of ethyl and the elements of sulphuric 
acid, C t H 5 S 2 2 . (Loewig, Kopp.) 

Bisulphuret of ethyl, C 4 H.S 2 =ES 2 , is a transparent oily liquid, boiling 
at 123.8° (51° cent.,) obtained by distilling a mixture of the double sulphate 
of ethyl and potash and the persulphuret of potassium. It is decomposed by 
caustic potash and by nitric acid (Zeise, Pyrame Morin.) 

Seleniuret of ethyl, is obtained, according to Loewig, in the same way as 
the sulphuret, substituting in the process seleniuret of potassium for the sul- 
phuret of potassium. 

Telluret of ethyl, obtained also by a similar process, using the telluret of 
potassium; a very volatile liquid of a deep orange colour (Wohler.) 

Cyanide of ethyl, hydrocyanic ether, C 4 H 5 +NC 2 ==ECy, obtained by 
Pelouze by exposing a dry mixture of sulphate of ethyl and potash to a gentle 
heat, which is gradually increased. It is a colourless liquid, with an insup- 
portable odour of garlic, boiling at 179.6° (82° cent.,) and of which the den- 
sity is 0.7. Sulphocyanide of ethyl has also been formed by distilling a mix- 

* Hence the name mercaptan v from mercurium. copfans. 



524 ETHYL. 

ture of sulphocyanide of potassium, alcohol and sulphuric acid. It is an oily- 
very dense liquid. 



SALTS OF OXIDE OF ETHYL, OR SALTS OF ETHER. 

Ether does not combine directly with acids, but these salts are obtained by 
the action of acids upon alcohol (hydrate of ether.) The neutral salts of ether 
are distinguished from inorganic salts by the circumstance that neither the 
acid nor oxide of ethyl can be replaced by double decomposition, at the ordi- 
nary temperature, by another acid or base, when the salt of it is mixed with 
another salt; the alcoholic solution of the oxalate of ether, for instance, not 
being precipitated by an alcoholic solution of chloride of calcium. These 
salts are decomposed by the alkaline hydrates, particularly when assisted by 
heat, their base attaching itself to the water of the alkaline hydrate, and coming 
off as alcohol, while their acid unites with the alkali. Several of these neu- 
tral salts are only partially decomposed by alkalies and metallic oxides, a 
neutral double salt being formed, in which the acid is united with equal pro- 
portions of oxide of ethyl and metallic oxide. The latter can again be re- 
moved by a stronger acid for which it has an affinity, and then an acid double 
salt is formed, in which the ethyl is combined with a salt of water. The 
metallic oxide of the neutral double salts can also be replaced by another me- 
tallic oxide, but the acid of the double salt is not affected by its usual precipi- 
tants, the sulphate of ethyl and potash, for instance, not being precipitated by 
chloride of barium. 

The acid salts of oxide of ethyl are not crystallizable, a concentrated solu- 
tion has a certain degree of stability, and may be heated to 212°, but a dilute 
solution decomposes spontaneously at the temperature of the air, and more 
rapidly when heated, with the formation of alcohol and a hydrate of the acid. 
Some of them, of which the hydrate is but slightly volatile, such as the acid 
sulphate of ether, are decomposed at a higher temperature into ether which 
escapes and acid which remains in the state of hydrate. 

The neutral salts of ethyl are generally derived from the acid sulphate of 
ethyl. When to a highly concentrated solution of the latter, solutions of other 
acids are added, it usually happens that the latter assume the oxide of ethyl 
to form neutral salts, and leave behind the hydrate of sulphuric acid; the mu- 
cate, oleate and stearate of ethyl are formed in this way. Or when to a simi- 
lar solution of the acid sulphate of ethyl, salts are added, of which the acids 
are volatile and form volatile compounds with oxide of ethyl, the sulphuric 
acid unites with the base of the other salt, while the volatile acid combines 
with oxide of ethyl, and distils over with the latter. 



ACID SULPHATE OF OXIDE OF ETHYL, OR SULPHATE OF OXIDE OF 
ETHYL AND WATER. 

Syn. Ethero sulphuric acid, sulphethylic acid (Mitscherlich,) sulphovinic 
acid; EO,S0 3 -f-HO,S0 3 . 

The neutral sulphate of ethyl has not yet been formed. 

The acid sulphate of ethyl may be formed directly by transmitting the 
vapour of ether through the hydrate of sulphuric acid so long as it is dissolved. 
On afterwards diluting that liquid with water, part of the ether separates in a 
free state, and part remains in combination with the acid. 

The same compound, however, is obtained from the action of sulphuric 



FORMATION OF ETHER. 525 

acid on alcohol, a chemical action which cannot yet be said to be fully ex- 
plained, although it has been the subject of much research. There are two 
steps in this action: 1. the production of sulphovinic acid, and 2. the libera- 
tion of ether. 

1. Formation of sulphovinic acid. — Equal weights of strong alcohol and oil of 
vitriol heated together to the boiling point of the mixture, and saturated at that 
temperature with milk of lime, give the sulphovinate of lime, or sulphate of 
ethyl and lime, which is soluble and may be separated by filtration from a 
considerable quantity of insoluble sulphate of lime, which is always formed at 
the same time. It is observed that the cooling and the dilution of the mixture 
of alcohol and sulphuric acid, before saturation, diminishes the proportion of 
sulphovinic acid, or of sulphovinate of lime formed, by causing a reproduction 
of alcohol. Even when the sulphuric acid is in great excess, a considerable 
proportion of alcohol, often nearly the half of it, escapes decomposition, or is 
not found in the sulphovinic acid when neutralized. That the whole alcohol, 
however, is at first converted into sulphovinic acid appears from the circum- 
stance that the mixture is not decomposed by a current of dry chlorine, no 
hydrochloric being formed, a property of sulphovinates, which undergo no 
modification by the action of chlorine, while free alcohol is immediately de- 
composed into hydrochloric acid and other chloruretted products. A mixture 
of 100 parts of oil of vitriol, 48 parts of alcohol, and 18.5 parts of water, 
which contains the elements of 2 atoms of sulphuric acid, 1 atom of ether, and 
6 atoms of water, boils at 284° (140° cent.,) and is not afTected by chlorine; 
it may be represented as (EO,S0 3 + HO,S0 3 )-f 5HO. 

The protohydrate of sulphuric acid, diluted with 55 per cent, of water, or 
HO,S0 3 +3HO, does not decompose alcohol at the ordinary temperature, 
but the reaction occurs when the mixture is boiled. 

It is observed by Mitscherlich that in the formation of sulphovinic acid, 
there is only a feeble disengagement of heat. If to two parts of alcohol, one 
part of sulphuric acid and then one part of water be added, the temperature of 
the mixture rises to 158° (70° cent.;) about half of the alcohol being con- 
verted into sulphovinic acid. While if to one part of sulphuric acid, one part 
of water be first added, and then two parts of alcohol, the temperature rises to 
154.4° (68° cent.,) or nearly as high, although in the last case no sulphovinic 
acid is formed. Consequently the heat evolved when sulphuric acid unites 
with oxide of ethyl is scarcely superior to that liberated when the protohy- 
drate of sulphuric acid unites with more water. : 

2. Formation of ether. — A mixture of 9 parts of hydrated sulphuric acid and 
5 parts of alcohol of 85 per cent, which is heated to the boiling point for ether, 
contains the elements exactly of I atom of the acid sulphate of ether, and 8 
atoms of water, or (EO,S0 3 + HO,S0 3 )-f 3HO. When this mixture is heated 
above 284°, the acid sulphate of oxide of ethyl is decomposed into ether and 
water, which distil over very nearly if not exactly in the proportions in which 
they exist in alcohol. The escape of ether from this mixture is not promoted 
by the addition of strong sulphuric acid to it, but on the contrary, retarded, 
and then requires a higher temperature. On the other hand, more alcohol 
added to the mixture distils off undecomposed in the anhydrous state. The 
water present in the ether mixture is necessary, and must act as a stronger 
base, displacing the oxide of ethyl in combination with the acid, and liberating 
it as ether (page 151.) Water may even displace so strong a base as ammo- 
nia, when assisted by the volatility of the latter ; a solution of the neutral sul- 
phate of ammonia becoming acid when boiled for some time, from the escape of 

* L'Institut, No. 390, p. 206 ; 17 Juin, 1841; where etherification and other theoretical 
questions are discussed by M. Mitscherlich. 



526 ETHYL. 

ammonia (Rose.) The addition, however, of more water to the ether mixture 
above, so as to lower its boiling point below 258.8° (126° cent.,) occasions the 
destruction of the sulphovinic acid, and then nothing but alcohol distils over. 

It was observed by Rose that ether begins to be slowly evolved from the 
ether mixture, at a temperature scarcely amounting to 212°; the ether is nearly 
pure, the water of the alcohol being retained at that temperature by the sul- 
phuric acid.* Liebig finds that on directing a current of dry air through the 
ether mixture heated to 284°, the point of ebullition falls to 273.2° (134° cent.,) 
and on examining what was carried away by the air, it was found to be nothing 
but alcohol.f The evolution of ether does not indeed proceed well, unless with 
a regular ebullition of the liquid. 

When the ether mixture contains a great excess of sulphuric acid, the decom- 
position of the sulphate of oxide of ethyl does not take place till the temperature 
rises to 320° (160° cent,) and then a variety of products are evolved, which 
Liebig refers to the re-action of the elements of sulphuric acid themselves upon 
oxide of ethyl. He supposes the elements of 1 atom of the acid sulphate of 
oxide of ethyl to divide themselves in the following manner : 

2 eq. of sulphurous acid . . . . S 3 4 
5 eq. of olefiant gas C 2 H 2 

3 eq. of water H 3 O s 

2 eq. of carbon, as residue ... C 2 



This appears to represent pretty well the decomposition by which olefiant gas 
is usually obtained (page 303 ;) but that gas may be obtained, according to 
Mitscherlich, accompanied by nothing but water, when sulphuric acid is diluted 
with water so as to boil at 320°, and the vapour of alcohol, containing 20 per 
cent, of water (density 0.844) is sent through it. After a part of the water is 
expelled by the heat, bubbles of olefiant gas appear in all parts of the liquid. 
The gas is accompanied by very little ether, and by almost no acid body ; and 
the liquid, even after it has produced a cubic foot of olefiant gas remains colour- 
less, without any deposite of carbon. The other substances obtained in the 
ordinary preparation of olefiant gas, Mitscherlich considers as secondary pro- 
ducts, which only begin to be formed when with alcohol of 80 per cent, a tem- 
perature is employed of 338° (170° cent.) 

In the ordinary decomposition of alcohol for olefiant gas, there is also formed 
a small quantity of the double sulphate of oxide of ethyl and etherole (oil of 
wine.) The carbonaceous residue has also been shown not to be pure carbon, 
but a compound substance, and named Thiomelanic acid by Erdman. Its' 
composition in its potash salt isC 80 H 24 S 3 O 20 -J-2KO. 

The solution of the acid sulphate of oxide of ethyl is a liquid of a very sour 
taste ; when diluted it cannot be concentrated by evaporation at any tempera- 
ture without decomposition. It is obtained in a state of perfect purity by heating 
slightly the sulphate of ethyl and etherole in contact with 4 parts of water ; the 
etherole (light oil of wine) separates and comes to the surface, while the acid 
sulphate of ethyl dissolves in the water. It forms a great number of double 
salts with bases, which to 2 atoms of sulphuric acid contain 1 atom of oxide of 
ethyl, and 1 atom of the base added. They are soluble in water, and in alcohol 
which is not anhydrous ; their sulphuric acid cannot be detected by the usual 
re-agents, but on boiling their solution with a few drops of hydrochloric acid, 

* H. Rose on Etherification, Taylor's Scientific Memoirs, vol. ii. 
t Traite de Chimie Organique, tome i, page 334. 



SULPHATE OF OXIDE OF ETHYL AND POTASH. 527 

alcohol is disengaged, and thereafter the presence of sulphuric acid can easily be 
detected in the residue. They are not decomposed by a current of gaseous 
chlorine ; the potash and soda salts are not decomposed when boiled with an 
excess of these alkalies ; the barytic salt distilled with sulphuric acid containing 
4 atoms of water gives a mixture of ether and alcohol ; concentrated solutions 
of all of them are gradually decomposed by ebullition. When a sulphovinate 
is submitted to dry distillation with hydrate of lime or barytes, it is converted 
into a neutral sulphate and alcohol. 

The sulphovinate of potash is the only anhydrous salt, all the oilers contain 
water of crystallization, which they generally lose when dried in vacuo at the 
ordinary temperature. The salts of potash, soda, and ammonia are prepared by 
precipitating the double sulphate of ethyl and lime or the salt of barytes, by the 
alkaline carbonates ; the double sulphate of ethyl and magnesia or manganese, 
by decomposing the double sulphate of ethyl and barytes, by means of soluble 
sulphates. 

These salts have all more the character of a bibasic salt, than of a double 
sulphate or compound of two monobasic sulphates, and may therefore be repre- 
sented as containing a sulphuric acid of double atom S 2 6 , which is bibasic, 
and is united at once with oxide of ethyl and another base, of which the last 
only can be displaced by other bases. They resemble the bibasic fulminate of 
silver, in which one atom only of base can be displaced by another base. 

Sulphate of oxide, of ethyl and potash, KO,EO-f-S 2 O c , crystallizes in colour- 
less plates like chlorate of potash, which have a saline and sweetish taste ; is 
persistent in air, soluble in an equal weight of water, also in dilute alcohol, but 
insoluble in anhydrous alcohol and ether ; above 212° it undergoes decomposi- 
tion without entering into fusion. 

Sulphate of oxide of ethyl, and barytes, BaO,EO-f S 2 6 -j-2HO, crystallizes 
in plates or rhomboidal prisms, persistent in air, and having a very acid taste. 

Sulphate of oxide of ethyl, and lime, CaO,EO-f S 2 6 +2HO. Five parts of 
this salt dissolve in 4 part's of water at 62.6 (17° cent.;) it is also soluble in 
alcohol with the aid of heat. 

Sulphate of oxide of ethyl, and oxide of lead, PbO,EO-f SoO a -f 2HO, crys- 
tallizes in large transparent tables, very soluble both in water and alcohol, and 
having an acid re-action. It slowly undergoes spontaneous decomposition, and 
becomes viscid from the formation of oil of wine. It dissolves an additional 
atom of oxide of lead, and becomes a basic salt, which becomes a white mass, 
and is very soluble. 

Acid phosphate of oxide of ethyl phosphovinic acid, 2HO,EO-f P0 5 , is 
formed on mixing alcohol with a concentrated solution of phosphoric acid, 
with the evolution of much heat; if the phosphoric acid is diluted so that its 
density does not exceed 1.2, it is not in a state to decompose alcohol. Phos- 
phovinic acid is a colourless, syrupy liquid, of an acrid and very acid taste, 
more stable than sulphovinic acid, as it may be boiled without decomposition, 
even when diluted. At a higher temperature it is decomposed, giving first 
ether and alcohol, then inflammable gases and a carbonaceous residue. When 
phosphovinic acid is treated with metallic oxides, the two atoms of basic 
water which it contains are separated and replaced by fixed base, while the 
oxide of ethyl remains, a tribasic class of salts being formed like the ordinary 
phosphates. The formula of the phosphate of ethyl and barytes is 2BaO, 
EO-f P0 5 -f 12HO. The compounds of pyrophosphoric acid and metaphos- 
phoric acid with oxide of ethyl have not yet been obtained (Pelouze.) 

Arseniate of oxide of ethyl, arseniovinic acid, HO,2EO-fAs0 5 , contains 2 
atoms of oxide of ethyl and 1 atom of basic water, which last may be replaced 
by fixed bases (D'Arcet.) 
Nitrite of oxide of ethyl, nitrous ether, C 4 H 5 0-J-N0 3 = EO,N0 3 . Ni- 



528 ETHYL, 

trie acid decomposes alcohol without combining with it» This ether may be 
obtained, however, by distilling 3 parts of strong alcohol with 2 parts of nitric 
acid of density 1.3, applying occasionally a very gentle heat, and condensing 
in a receiver surrounded by ice. But as prepared with nitric acid, by this 
and other processes, nitrous ether always contains aldehyde, a product of the 
oxidation of alcohol. M. Liebig recommends as the best process for nitrous 
ether, to transmit a current of nitrous acid vapour, obtained by heating on a 
water-bath a spacious retort, containing 1 part of starch and 10 parts of 
nitric acid of 1.3, through a mixture of 2 parts of alcohol of 85 per cent, and 
1 part of water, contained in a bottle of two tubulures, and surrounded by 
cold water. The nitrous acid is immediately absorbed by the alcohol, and 
combines with ether. The product, at the same time, distils over, and may 
be conducted from the vessel in which the reaction takes place, by means of a 
glass tube, to a tube condenser. 

Nitrous ether, in a state of purity, is a volatile liquid, of a pale-yellow 
colour, possessing the agreeable odour of the Normandy rennet. Its density 
at 59° (15° cent.) is 0.947; it boils at 61.5° (16.4° cent.) It is converted by 
the tincture of hydrate of potash into nitrate of potash and alcohol. 

Carbonate of oxide of ethyl, carbonic ether, EO,C0 2 ; obtained by M. 
Ettling, by the action of potassium or sodium on oxalic ether; a colourless 
aromatic liquid, of density 0.965 at 66.2° (19° cent.,) boiling at 258.8° (126° 
cent.) 

Carbonate of oxide of ethyl and potash, KO,EO-f C 2 4 ; is prepared by 
dissolving in alcohol hydrate of potash, fused and still red hot, and saturating 
the solution with dry carbonic acid gas. When purified, it crystallizes in 
silky laminae, soft to the touch (Dumas and Peligot.) 

Oxalate of ether, oxalic ether, EO,C 2 3 . The following process is given 
by M. Liebig, from Ettling, for the preparation of this which is one of the 
most interesting of the ethers. A mixture is distilled rapidly of 4 parts of 
binoxalate or quadroxalate of potash, 5 parts of oil of vitriol, and 4 parts of al- 
cohol of 90 per cent. (0.818.) As soon as the liquid which passes is troubled 
by an addition of water, it contains oxalic ether, and is collected in a receiver 
which is not cooled. The product is afterwards mixed with 4 times its 
volume of water; the ether then separates, and it is agitated immediately with 
pure water, which is renewed frequently, till an acid reaction ceases to be 
manifested. 

The washed ether is rectified in a small dry retort, which is filled to 
9-10ths; as soon as the product which passes is colourless and transparent, and 
the liquid boils tranquilly in the retort without bumping, it is necessary to 
change the receiver, for from that period the oxalic ether distils over, pure 
and anhydrous. The residue in the retort contains some traces of oxalic acid. 
(Traite, p. 350.) 

Oxalic ether is a colourless liquid, of an aromatic odour; its density 1.0929, 
and boiling point 363.2° (180° cent.) When pure it may be kept in contact 
with water for several days without decomposition, but if it contains the smallest 
trace of acid or alcohol, it is decomposed rapidly into oxalic acid and alcohol. 
The fixed alkalies act upon it in the same manner as water. 

By ammonia or solution of ammonia in excess, oxalic ether is instantly 
decomposed, a beautiful white precipitate of oxamide (page 291) appearing 
and alcohol is reproduced: 

NH 3 and EO,C 2 3 , = NH 2 ,C 2 2 (oxamide) and EO,HO (alcohol.) 

Oxalate of ether and oxamide, or oxamethane; EO,C 2 3 -f NH 2 ,C 2 2 ; 
or C 3 H 7 N0 6 , is a substance in beautiful white crystalline leaflets, formed by 
adding alcohol saturated with ammoniacal gas to a solution of oxalic ether in 



COMPOUND ETHERS. 529 

alcohol. It is fusible about 212°, distils at 428° (220° cent.) without altera- 
tion. Four atoms of the hydrogen of this compouud can be replaced by 

chlorine, and chloroxamethane formed, C 8C , 3 N0 6 , which strikingly re- 
sembles oxamethane in its physical properties, and is even believed to be 
isomorphous with it. 

Oxalate of oxide of ethyl and potash, oxalovinate of potash, KO,EO-f 
C 4 6 . This salt is prepared by adding to a solution of 1 volume of oxalic 
ether in 2 volumes of alcohol, somewhat less than half the potash dissolved in 
alcohol, which would be required to form a neutral salt with the oxalic acid 
of the ether; the salt precipitates, being insoluble in the alcohol. It is anhy- 
drous. 

Acid oxalate of oxide of ethyl and water, oxalovinic acid, H0,E0-fC 4 
6 , is obtained by treating an alcoholic solution of the preceding salt with 
hydrofluosilicic acid, or by decomposing with caution an aqueous solution of 
the oxalate of ethyl and barytes by dilute sulphuric acid. It is a very acid 
liquid, which is decomposed by evaporation. 

Su/pho carbonate of oxide of ethyl and potash, xanthaie of potash of Zeise; 
KO,EO-f C„S 4 . This salt contains 2 atoms of bisulphr.rct of carbon, united 
with 1 of potash and 1 of oxide of ethyl. It is formed on pouring the bisul- 
phuret of carbon into absolute alcohol saturated cold with hydrate of potash, 
and keeping the mixture at a gentle heat; the liquor becomes a crystalline 
mass of the salt at 32°. The salt crystallizes in colourless or yellowish crys-. 
tals. 

Sulpha carbonate of oxide of ethyl and water or xanthic acid., HO,EO-f 
C 2 S 4 , is obtained as an oily liquid, insoluble in water, when the preceding 
potash salt is decomposed by dilute sulphuric or hydrochloric acid. 

Bicyanurate of oxide of ethyl, cyanic ether, 3EO-f 2Cy 3 3 +6HO. This 
compound was obtained by Liebig and W center by directing the vapours of 
hydrated cyanic acid into a mixture of alcohol and ether, as long as they were 
absorbed. The compound crystallizes after twenty-four hours' repose, and is 
purified from cyamelide, with which it is accompanied, by solution in boiling 
alcohol or water and a second crystallization. Its solution is neutral to test 
paper, and it does not form compounds with metallic oxides. 

Benzoate of oxide ethyl. benzoic e//ier, G^HjO-r-C, jHjCK = EO,BzO. This is 
a liquid ether, of density 1.0539 at 50° (10° cent.,) boiling at 408.2° (210° cent.,) 
prepared by distilling a mixture of 4 parts of alcohol of 83 per cent. (0.840) 
with 2 parts of crystallized benzoic acid, and 1 part of concentrated hydrochlo- 
ric acid. 

Hippurale of oxide of ethyl, hippuric ether, C 4 H.O + C lfi H 8 N0 5 . This 
compound was first prepared by Dr. Stenhouse. It is obtained in fine crystal- 
line needles, perfectly white, and of a silky lustre. The crystals are not volatile, 
their density is 1.043 at 73.4° (23° cent.;) they fuse at 109.4° (43° cent.) 

Chloroxi-carbonic e//jer,C 4 H 5 0-j-C 2 3 Cl. This name has been given by 
M. Dumas to an ethereal liquid, which is formed when absolute alcohol is 
brought into contact with chloro-carbonic acid gas (page 272.) Its density is 
1.33 at 59°; it boils at 201.2° (94° cent.) 

Ur ethane, C 6 H 7 O t N. This substance is formed, with sal-ammoniac, on 
dissolving the preceding compound in solution of ammonia. Purified by dis- 
tillation, it is a pearly- white, crystalline substance, resembling spermaceti ; it fuses 
at 212°, and distils without change at 356° (180° cent.) Urethane may be 
considered as a chloroxicarbonic ether, in which the chlorine is replaced by 
by amidogen, C a H 5 0-f C 2 3 (NH S .) It may also be looked upon as the pro- 
duct of the combination of 2 atoms of carbonic ether with 1 atom of urea, 
45 



530 ETHYL. 

2C 5 H 5 3 -f-C 2 2 ,N 2 H 4 , the consideration which induced M. Dumas to give it 
the name of urethane. 

Some other compound ethers or neutral salts of oxide of ethyl will be de- 
scribed under their respective acids. 



TRANSFORMATIONS OF THE BODIES CONTAINING ETHYL. 

The compound of alcohol and chloride of zinc was found by M. Masson to 
give ether and water when heated to 284°, and at a higher temperature, be- 
tween 320° and 392°, two liquid hydrocarbons,- one boiling at 212° represented 
by C 8 H 7 , and the other boiling at 572° (300° cent.) C 3 H 9 ; the sum of which 
is CjgHj g , exactly the composition of olefiant gas. The liquid long known as 
oil of wine is probably one of these hydrocarbons. It is found in the retort 
from which a considerable quantity of crude ether has been distilled off lime. 

Sulphate of oxide of ethyl and of etherole, C 4 H 5 0,C 4 H 4 -fS 2 6 , long 
known as the sweet oil of wine or the heavy oil of wine. This compound arises 
from the decomposition of the neutral sulphate of oxide of ethyl, which cannot 
exist in an isolated state, and is best obtained by distilling 3 atoms of the sul- 
phovinate of lime with 1 atom of caustic lime ; these give 1 atom of sulphate of 
oxide of ethyl and etherole, 1 atom of alcohol, and 4 atoms of sulphate of lime. 
The sulphate of oxide of ethyl and of etherole is a colourless oily and aromatic 
liquid, of density 1.33, boiling at 536° (280° cent.,) and capable of being dis- 
tilled without alteration, if free from water. It is decomposed by water and by 
acids into sulphovinic acid and etherole. Etherole, first observed by Mr. Hen- 
nel, and sometimes called the light oil of wine, is an oily liquid, of density 
0.917, boiling at 536°. Etherole submitted to a low temperature, deposits 
crystals of etherine, which are long prisms of great lustre, fusing at 230° and 
boiling at 500° (260° cent;) of density 0.980. These two compounds are iso- 
meric, and consist of carbon and hydrogen, in the same proportions as in ole- 
fiant gas. 

Ethionic and isethionic acids, produced by M. Magnus, by the action of an- 
hydrous sulphuric acid on absolute alcohol. A crystalline compound of olefiant 
gas and anhydrous sulphuric acid was obtained by M. Regnault, which may be 
separated by C 4 H 4 -f 4S0 3 , or by C 4 H 4 0,S 2 5 -f2S0 3 , that is, as containing 
hyposulphuric acid united with another base, different from oxide of ethyl, with 
sulphuric acid. A crystalline compound was also obtained by Magnus, by ex- 
posing absolute alcohol to the vapour of anhydrous sulphuric acid, and named by 
him carbyle, which appears to be the same. Saturated with carbonate of barytes, 
carbyle gave free sulphuric acid [sulphate of barytes 1] and the soluble ethionate of 
baryles, which last contains the same elements as sulphovinate of barytes, indi- 
cating the assumption of the elements of an atom of water by the carbyle. Ethi- 
onic acid may be procured by adding dilute sulphuric acid cautiously to a solution 
of ethionate of barytes. It is a compound of small stability, and is decomposed by 
boiling like sulphovinic acid, giving alcohol and isethionic acid, the last of which 
does not undergo farther decomposition. The salts of the latter are likewise 
isomeric, when dried, with the sulphovinates. Isethionic acid may be concen- 
trated, and stands 302° (150° cent.) without decomposition. All its salts are 
neutral to test-paper, and are also remarkably stable, supporting a temperature 
of 482° (250° cent.) without decomposition. When fused with an alkaline hy- 
drate, they leave as a residue a mixture of the sulphite and sulphate of the 
alkali, from which it is inferred that they contain hyposulphuric acid, and not 
sulphuric acid. 

Jsethionate of barytes is prepared by passing pure olefiant gas through an- 
hydrous sulphuric acid, in the liquid state; or by saturating ether in a flask 



ACETYL. 531 

surrounded with ice, by the same acid. The acid solution 13 afterwards boiled, 
so long as alcohol is disengaged, and then saturated with carbonate of barytes. 
This salt is represented by BaOjC^BsOj-f S 2 €> 5 . Isethionate of copper 
crystallizes in regular octohedrons, of an emerald green colour, containing 2 
atoms of water of crystallization, which they lose at 482° (250° cent.,) and 
become white and opaque. From none of these salts can alcohol or ether be 
derived; they do not, therefore, contain ethyl. 

Two other acids of this class have been obtained, methionic acid, by satu- 
rating ether with anhydrous sulphuric acid, without cooling the mixture, of 
which the salt of barytes, BaO,C 2 H 3 S 2 7 , is insoluble in alcohol; and al- 
thionic acid, which is found in the residue of the preparation of olefiant gas 
by means of alcohol and sulphuric aeid, of which the salts are isomeric with 
the sulphovinates, although distinguishable from them by their properties 
(Ettling, Regnault.) 

The compounds which follow are derived from the oxidation of alcohol and 
its derivatives. 



SECTION III. 



ACETYL SERIES OF COMPOUNDS. 

Acetyl C 4 H 3 = Ac: a hypothetical radical, produced by the abstraction of 
2 atoms of hydrogen from ethyl, by oxidating processes, and which pervades 
a series of compounds, including acetic acid, from which it derives its name. 

The following are the oxygen compounds of acetyl. 



Acetyl .... 


• C 4 H S 


Oxide of acetyl 


. C 4 H 3 . unknown 


Hydrate of oxide of acetyl 


. C 4 H,0 +HO aldehyde 


Acetous acid 


. C 4 H 3 2 +HO aldehydic acid 


Acetic acid 


. C 4 H 3 3 -fIIO acetic acid. 



HYDRATE OF THE OXIDE OF ACETYL, OR ALDEHYDE*. 

Formula, C 4 H 3 + H0. It will be observed that aldehyde occupies the 
same place in the acetyl series that alcohol does in the ethyl series. It was 
obtained in an impure state by Dobereiner, and afterwards isolated, and its true 
nature ascertained by Liebig. Aldehyde is formed by the aetion of oxidating 
bodies upon alcohol, by which 2 atoms of hydrogen are abstracted, and the 
elements of aldehyde left. It is occasionally produced during the absorption 
by alcohol of oxygen from the air, in the process of acetification, and is a 
product of the action of dilute nitric acid upon alcohol, but it is usually pre- 
pared by the action of dilute sulphuric acid with peroxide of manganese upon 
alcohol. 

To prepare aldehyde, a mixture is distilled by a gentle heat of 6 parts of sul- 
phuric acid, 4 parts of water, 4 parts of rectified spirits of wine, and 6 of perox- 
ide of manganese, and the product carefully condensed, so long as chemical 
action appears to take place from the frothing up of the materials in the retort. 

* From alcohol dehydrogenatum. 



532 ACETYL. 

The distilled liquid, which is a mixture of aldehyde with water and several other 
secondary products, is distilled by a water-bath from an equal weight of chlo- 
ride of calcium, till one half of it passes over. But to free the aldehyde from 
foreign bodies, it is necessary to unite it with ammonia ; the product of the last 
distillation is therefore diluted with an equal volume of ether, and the mixture 
saturated at a low temperature with ammoniacal gas ; the compound, or am- 
monia-aldehyde is deposited in colourless crystals, which are afterwards washed 
with ether and dried in air. Two parts of ammonia-aldehyde dissolved in 2 
parts of water are distilled with 3 parts of sulphuric acid diluted with 4 parts of 
water, and the product condensed in a receiver surrounded with ice. It is 
afterwards rectified from chloride of calcium, by a heat not exceeding 77 or 86° 
(25 or 30° cent.) 

Aldehyde is a colourless, highly-fluid liquid, of a peculiar ethereal and suffo- 
cating odour, boiling at 71.6° (22° cent.) of density 0.790 at 64.4° (18° cent.,) 
neutral, and very combustible. It is miscible with water, alcohol and ether. It 
changes in the air into acetic acid by absorption of oxygen. It dissolves phos- 
phorus, sulphur and iodine. 

When pure and anhydrous aldehyde is kept for some time at 32°, it gradually 
loses its power mix with water, and is transformed into a coherent mass, com- 
posed of long transparent needles, resembling icy spicules. This is Elaldehyde, 
which is similar in composition to aldehyde, but of three times the atomic weight, 
judging, from the density of its vapour. Elaldehyde fuses at 35.6° (2° cent.,) 
and boils at 201.2° (94° cent.) 

■ Met aldehyde is another product of the condensation of the elements of alde- 
hyde, which appears at the ordinary temperature in aldehyde left for some time 
in a well-stopped phial, in the form of white and transparent needles, or colour- 
less prisms, which gradually attain a certain magnitude. It sublimes at 248°" 
without fusing, and condenses in the air in snowy und very light flocks. It is 
insoluble in water, but dissolves easily in alcohol. The density of its vapour 
has not been determined. 

Aldehyde is capable of combining directly with ammonia and potash, thus 
evincing an approach to the acid character. 

*ftmmonia-aldehyde,C 4H 3 0,~NH 3 + HO, crystallizes in acute rhombohedrons, 
which are transparent and of great lustre. These crystals fuse between 70 and 
80° cent, and distil without alteration at 1 00° cent. 

Jicetal, or compound of aldehyde with ether, AcO,EO-r-HO=C 8 H 9 3 , was 
discovered by Dobereiner, and is formed by the action of platinum black on the 
vapour of alcohol with the presence of oxygen. Acetal is a colourless very 
fluid liquid, having a peculiar odour, suggesting that of Hungary wines. It 
boils at 95.2° cent, its density is 0.823 at 20° cent. It is soluble in 6 or 7 parts 
of water, and mixes with alcohol in all proportions. 

Resin of aldehyde is a product of the decomposition of aldehyde by alkalies, 
with the assistance of air. 



ACETOUS OR ALDEIIYDIC ACID.. 

Formula of the hydrated acid, C 4 H 3 2 -f-HO=Ac0 2 -f HO.— This acid is 
formed when aldehyde is heated in contact with oxide of silver, one half of the 
oxide being reduced to the metallic state, while the other half unites with the 
aldehydic acid formed. If to water in a test-tube containing a few drops of 
aldehyde, a little nitrate of silver be added, and ammonia so as to precipitate 
the oxide of silver, and then the tube be rapidly heated by the flame of a spirit- 
lamp, the silver is deposited on the tube with a bright, surface, like a mirror, and 



ACETIC ACID. 533 

forms a beautiful experiment. When the salts of this acid are evaporated, they 
become brown, and undergo decomposition. 



ACETIC ACID. 

Formulae of the hydrated acid HO-f C 4 H 3 3 =HO-f Ac0 3 . 

Vinegar has long been derived by the action of air upon alcoholic liquors-, such 
as wine and beer, but the remarkable discovery of Dr. J. Davy, that platinum 
black in contact with alcohol became incandescent, and gave rise to acetic acid, 
first led Dobereiner to the discovery that alcohol by absorbing oxygen gives 
rise to water and acetic acid, without disengaging carbonic acid. He found 
that the elements of 1 atom of alcohol absorb 4 atoms of oxygen, with the for- 
mation of 1 atom of anhydrous acetic acid, and 3 atoms of water. 

C 4H 6 ° 2 aQ d 4 ° = C 4 H 3 3 and 3H0. 
or C 4 H 5 0-fHO and 40 =* HO,C 4 H 3 3 ,+2HO. 

Hence, when alcohol is converted into acetic acid, 2 atoms of oxygen are 
directly absorbed, and 2. atoms of oxygen convert 2 atoms of hydrogen into 
water. The atom of water of the alcohol and the 2 atoms of water produced, 
are all retained, and form a remarkable terhydrate of acetic acid. 

Pure alcohol, diluted with water and exposed to- air, does not acidify; the 
presence of some foreign organic matters, which exist in wine and beer, is 
necessary to act as a ferment, and to place the alcohol in a condition to absorb 
oxygen. This ferment is no doubt an oxidable azotised matter. Some kinds 
of beer, in which the ferment ha3 been completely exhausted and precipitated 
by a preceding highly protracted vinous fermentation, such as the Bavarian 
beer, are not liable to become sour or undergo the acetous fermentation. The 
rapid process of acidifying alcohol, introduced into Germany by MM. Wage- 
man and Schuzenbach, is the most interesting, in a scientific point of view. 

Strong alcohol is diluted with 4 or 6 parts of water, and about 1-1 000th of 
yeast, must of beer, vinegar or honey added to it. To acidify this liquid, it 
is heated to 75 or 80°, and made to trickle through a 
cask, filled' with beech-wood shavings, (Fig. 126,) and Fig. 126. 

pierced with holes at top and bottom to allow a circu- 
lation of air through it. From the great surface ex- 
posed by the liquid, the absorption of oxygen is most 
rapid, and the temperature rises to 100 or 104°. 
When the liquid has been passed three or four times 
through the barrel, at the high temperature, all the al- 
cohol it contains is changed into vinegar; an operation 
which may be completed in twenty-four or thirty-six 
hours. The addition of certain aromatic substances, 
such as the essential oils, or a mere trace of wood 
vinegar, entirelv prevents the acidification of the alco- 
hol. ^ 

Wood vinegar, or pyroligneous acid is prepared on a large scale by the dis- 
tillation of wood, generally that of oak coppice deprived of the bark, which is 
used in tanning. The watery fluid containing the acid, and tarry matter which 
distil over together, are separated, mechanically, in a great measure, by subsi- 
dence. The acid may be freed from a portion of the empyreumatic oils it 
holds in solution, by a single distillation. It is purified completely by neu- 
tralizing it with lime, crystallizing the acetate of lime repeatedly, decomposing 
the latter by sulphate of soda, and fusing the acetate of soda by a high tempe- 

45* 




534 ACETYL. 

rature, at which, the empyreumatic matters are volatilized or destroyed. By 
distilling 3 parts of the acetate of soda, well dried and in powder, with 9.7 
parts of sulphuric acid, a highly concentrated and pure acetic acid is obtained. 

The proportions last mentioned give 2 parts of ahydrated acetic acid, which 
is distilled again, and the last two thirds of the distilled liquid exposed to 24 or 
25°, for the protohydrate of acetic acid, which crystallizes. The crystals 
may be drained, fused, and crystallized again, to obtain the hydrate of acetic 
acid in a state of purity. Below 63°, the hydrate crystallizes in shining trans- 
parent plates or tables, which fuse above 63° into a limpid liquid, of density 
1.063; it boils at 248°. The odour of this acid is penetrating and character- 
istic; it forms blisters on the skin, like a mineral acid. The liquid acid mixes 
with water, alcohol, ether, and several essential oils in all proportions. It 
dissolves camphor and some resins. The vapour of the acid in a state of 
ebullition may be kindled, and burns with a pale blue flame, producing water 
and carbonic acid. Nitric acid has no action on acetic acid; sulphuric acid 
with heat blackens acetic acid, with an evolution of sulphurous acid. 

Acetic acid increases somewhat in density by a slight dilution; the greatest 
condensation occurring in the hydrate consisting of 1 atom of anhydrous 
acid and 3 atoms of water, of which the density is 1.07. The strength of a 
dilute acetic acid is best ascertained by the quantity of marble it dissolves. 

Acetic acid forms neutral salts, and with many metallic oxides sub-salts con- 
taining 2 and 3 atoms of base to 1 atom of acid. Most of its neutral salts are 
soluble. It is recognised in combination by the peculiar odour of acetic acid 
evolved when concentrated sulphuric acid is added. M. Liebig recommends 
as the most certain means of discovering the presence of acetic acid, or of 
an acetate in any substance, to distil it with dilute sulphuric acid, and to place 
the product in contact with oxide of lead in the cold. If there is any acetic 
acid present, the oxide of lead dissolves, and the solution exhibits an alkaline 
reaction. (Traite, i. 338.) 

Acetate of oxide of ethyl, acetic ether, C 4 H 5 .0-fC 4 H,0 3 =EO,A. Alcohol 
is only decomposed to a small extent when distilled with strong acetic acid. 
The ether is prepared by distilling, with a heat moderate at first, but afterwards 
increased 4.5 parts of strong alcohol and 6 parts of concentrated sulphuric acid,. 
previously mixed and cooled, with 10 parts of anhydrous acetate of lead. The 
product is neutralized with a little lime, then poured over an equal bulk of chlo- 
ride of calcium in a tubulated retort, and distilled again by a water-bath. Acetic 
ether is a liquid of an agreeable refreshing odour, and i3 the source of the re- 
freshing odour of some kinds of vinegar which contain it. Its density is 0.89 
at 59° ; it boils at 165.2° (74° centig.) Acetic ether is soluble in 7 parts of: 
water, 'and in alcohol and ether in all proportions. It is decomposed by alka- 
lies with the greatest facility. 

Acetic acid forms neutral and bisalts with the alkalies. The neutral solution 
of acetate of ammonia, the spirits of mindererus,is used in medicine. Acetate 
of potash is a foliated crystalline mass, anhydrous, and slightly deliquescent. 
Acetate of soda crystallizes with 6 atoms of water; it is soluble in three 
times its weight of cold water, and in five times its weight of alcohol. Its taste 
is saline, cooling and agreeable. Acetate of barytes crystallizes below 59° with 
3 atoms of water, and is isomorphous with acetate of lead; at a higher tempera- 
ture it crystallizes with 1 atom of water. It is very soluble in water, and more 
so at a low than at a high temperature. Acetate of strontian crystallized below 
59° (15° cent.) contains 4 atoms of . wateiv and crystallized above that tempera- 
ture only half an equivalent of water. Acetate of lime crystallizes with water,,. 
A concentrated and boiling solution of. it treated with sulphate of soda, in the 
preparation of acetate of soda, allows a double sulphate of lime and soda, 



OXICHLORIDE OF ACETYL. 535 

to precipitate. Acetate of magnesia is very soluble, and crystallizes with dif- 
ficulty. 

Acetate of alumina is obtained in solution, when acetate of lead, barytes or 
lime is precipitated by sulphate of alumina, and is much used in dyeing. This 
salt is decomposed in drying, or by a slight heat, into free acetic acid and a 
subacetate of alumina which is insoluble. The solution of the pure salt may 
be boiled without decomposition, but if sulphate of potash, or any other neutral 
salt of an alkali be present, the solution becomes turbid when heated, and a 
basic salt precipitates, which dissolves again on cooling (Gay-Lussac.) Acetate 
of manganese is used in dyeing, and is prepared for that purpose by mixing 
acetate of lime with sulphate of manganese. This salt is crystallizable. Ace- 
tate of zinc crystallizes with 3 atoms of water. Acetates of iron: a mixture 
of the acetates of protoxide and peroxide of iron, employed as a mordant for 
dyeing black, is prepared directly by dissolving old iron hoops, &c. in crude 
wood vinegar, with access of air. The acetates of lead have already been de- 
scribed (page 412;) also the acetates of copper (page 406,) acetate of black ox- 
ide of mercury (page 451,) and acetate of silver (page 463.) 



SECTION IV. 



PRODUCTS OF THE ACTION OF CHLORINE, BROMINE, AND IODINE 
UPON ETHYL, ACETYL, AND THEIR COMPOUNDS. 

Oxichloride of acetyl, C 4 H 3 C1 2 0,(1,) is an oily colourless liquid, obtained by 
saturating anhydrous ether with dry gaseous chlorine, cooling the mixture at 
the beginning, and heating it towards the end of the operation. As in the for- 
mation of acetic acid, 2 atoms of hydrogen are oxidated and withdrawn by 
the action of the oxygen of the air upon alcohol, and replaced by 2 atoms of 
oxygen, so in the action of chlorine upon alcohol, a similar change occurs of 
which the product is the oxichloride of acetyl. When heated with potassium, 
this compound gives chloride of potassium, and a gaseous body, containing 
only half the chlorine in the original substance, or C 4 H 3 C10, (2) observed by 
Malaguti. By the action of chlorine upon the vapour of pure ether in sun-shine 
Regnault obtained another crystalline compound C«C1 5 0, (3,) in which the 
whole hydrogen of ether is replaced by chlorine. Felix d'Arcet has also ob- 
served an accessory product in the preparation of Dutch liquid, which had the 
composition C 4 H 4 C10, (4.) It is named chloretheral by him. It will be observed 
that the fourth, first and third of these bodies are compounds, in which 1,2 and 
5 atoms of the hydrogen of chloride of ethyl are replaced by chlorine, without 
any other change of composition. They are all neutral bodies. 

Oxisttlphuret of acetyl, C 4 H 3 S 2 0; a compound in which 2 atoms of the 
hydrogen of oxide of ethyl are replaced by 2 atoms of sulphur, is obtained by 
the action of sulphuretted hydrogen upon the oxichloride of acetyl. Another 
compound is formed at the same time, in which 1 atom of chlorine remains, 
and only 1 atom of sulphur is introduced, C 4 H 3 C1S0. 

Acetate of oxichloride of acetyl, C 4 H 3 Cl 2 0-fA, a body formed by the ac- 
tion of chlorine upon acetic ether, in which 2 atoms of the hydrogen of the 
ether are replaced by 2 atoms of chlorine; or the oxichloride of acetyl is 
formed, and continues in combination with the acetic acid. The benzoate of 
oxide of ethyl gives a compound, of which the formula is BzCl-f C 4 H 3 
C1 2 0. 

Chlor oxalic ether, C 6 Cl 5 4 orC 4 Cl 5 + C 2 3 ; formed by the action of 



536 



ACETYL. 



chlorine on oxalic ether, crystallizable, fusible at 291°, not volatile. Clorox- 
amethane, C 6 Cl 5 O d + C 2 2 ,NH 2 ; formed by the action of ammoniacal gas 
on the ether, crystallizable, fuses at 273°, boils above 392°, volatile. Chlo- 
roxalovinic acid is obtained by the action of solution of ammonia upon chlo- 
roxamethane (Malaguti, An. de Chim. lxxiv, 299.) 

Chloride of acetyl, fyc. — The following table exhibits the composition and 
some of the properties of the series of compounds formed by Regnault, by 
treating the chloride of ethyl and the products thus obtained, successively with 
chlorine (An. de Ch. lxxi,*353:) 



4 vol. 









Density 




Spec. grav. 


Boiling point. 


of vapour 


caci, 


0.874* 


11° centig. 


2219 


C 4 H 4 C1 S 


1.174 


64° . . 


3478 


C 4 H 3 C1 3 


1.372 


75° . . 


4530 


C 4 H 2 C1 4 


1.530 


102° . . 


5799 


C.H.Cl, 


1.644 


146° . .. 
CHLORAL. 


6975 



Formula: C 4 HCl 3 2 ==e 4 Cl 3 + HO. 

This singular liquid, of which we owe the discovery to> Liebig, may be 
considered as the hydrate of oxide of acetyl (aldehyde*) in which the whole 
hydrogen of the acetyl is replacecfcby chlorine: 

Hydrate of oxide of acetyl .. . . C 4 H 3 + HO. 
Chloral ........ '. C 4 C1 3 0+HO. 

It cannot, however, be prepared directly by the action of chlorine upon 
aldehyde, owing to the facility with which the latter body changes, but it is 
the ultimate product of the action of chlorine upon anhydrous alcohol. It is 
recommended in preparing chloral, to introduce a few ounces of perfectly an- 
hydrous alcohol into the body of a tubulated retort, supported with its beak 
somewhat elevated, and with a glass tube adapted by a cork to the mouth, 
and directed upwards, so that what condenses may flow back into the body of 
the retort. Chlorine gas carefully dried by being passed through sulphuric 
acid, which is renewed from time to time during the process, is conducted by 
a tube entering the tubulure of the retort, and made to stream through the 
alcohol, the body of the retort being immersed in cold water to keep it cool at 
the beginning, but afterwards heated to assist in expelling the hydrochloric 
acid formed, towards the end of the process. An immense quantity of chlo- 
rine is required, and the gas may continue to be absorbed by a few ounces of 
alcohol for twelve or fifteen hours. The operation is complete when the 
chlorine traverses the boiling liquid without any disengagement of hydrochloric 
acid; a dense oleaginous liquid, the hydrate of chloral; is obtained, which often 
becomes a solid mass on cooling. The mass m fused by a gentle heat, and 
mixed in a well-stopped bottle, with two or three times its bulk of oil of vitriol, 
and the mixture gently heated by a water-bath; the impure chloral comes to 
the surface of the liquid, in the form of a limpid oil. It is drawn off, and 
boiled for some time to expel free hydrochloric acid and alcohol, and then dis- 
tilled from an equal bulk of sulphuric acid, to deprive it of adhering water. 

The last product is pure chloral,, except a little hydrochloric acid, which is 

t 

* At 11° cent.; the others between 18 and 20° cent. 



CHLORAL. 537 

separated by distilling again from quicklime slaked and recently ignited, dis- 
continuing the distillation when the lime in the retort is no longer covered by 
the liquid; the product obtained is chloral, perfectly pure. (Liebig.) 

Chloral is a pretty fluid oleaginous liquid, colourless, greasy to the touch, 
having a penetrating disagreeable odour which provokes tears ; its taste is first 
oily and then caustic. Its density is 1.502 at 64.4° (18° cent.,) and it boils at 
201.2° (94° cent.) distilling without alteration ; the density of its vapour is very 
nearly 5000, and its combining measure, 4 volumes (Dumas.) Chloral is mis- 
cible with alcohol and ether ; it dissolves, apparently without alteration, sulphur, 
phosphorus and iodine, with the aid of heat. 

Hydrate of chloral— Chloral is first obtained from alcohol in the state of a 
hydrate, the water being derived from a reaction of the nascent hydrochloric 
acid and alcohol, which gives rise to water and chloride of ethyl. When pure 
chloral is brought in contact with a small qauntity of water, combination takes 
place immediately on mixing the liquids, with evolution of heat, and in a few 
seconds the compound is deposited as a crystalline mass, composed of needles, 
which re-dissolve in a larger quantity of water. By evaporation of the solution 
in vacuo, the compound is obtained in large rhombohedral crystals, which con- 
tain 2 atoms of water. The solution of the hydrate of chloral is neutral, and 
has no action on red oxide of mercury ; the dry hydrate may be distilled with- 
out change. 

Insoluble chloral. — Like aldehyde pure chloral cannot be kept long without 
alteration. It gradually passes into a solid mass resembling porcelain, without 
change of weight, and equally whether contained in vessels which are hermeti- 
cally sealed or open. This mass is not dissolved by water, but when placed in 
contact with a very small quantity of water, it slowly changes into the crystal- 
line hydrated chloral, which dissolves at once when a large quantity of water is 
added to it. Insoluble chloral is modified by contact with sulphuric acid, and 
somewhat altered in composition ; when washed with water it loses a little hy- 
drochloric acid, and acquires some water. The formula assigned to modified 
insoluble chloral isC, 2 H 4 C1 & 7 : which is 3 atoms of chloral, minus 1 atom of 
hydrochloric acid plus 2 atoms of water. 

Sulphuret of ether ivith chlorine. — Regnaulthas observed that the sulphuret 
of ethyl is powerfully acted upon by chlorine with the assistance of light ; 4 
atoms of hydrogen are replaced by 4 atoms of chlorine, and the compound C 4 
CI t HS formed, which is a fetid liquid boiling about 320° (160° cent. ;) of density 
1.673 at 75.2° (24° cent.) 

Chloracetic acid, C^Cl^Oj-f HO. — This remarkable acid, in which the 3 
atoms of the hydrogen of acetic acid are replaced by 3 atoms of chlorine, was 
obtained, by M. Dumas, by the action of chlorine gas contained in large bal- 
loons upon the hydrate of acetic acid, exposed to the direct rays of the sun for 
a whole day. It crystallizes in rhomboid al plates of colourless needles, which 
deliquesce rapidly in damp air. Chloracetic acid whitens the tongue ; its va- 
pour is suffocating and painful to the organs of respiration. It reddens litmus, 
without bleaching it. The crystals fuse at 45 or 46° cent. ; and fused they en- 
ter into ebullition between 195 and 200° cent. The density of the fused acid 
at 46° cent, is 1.617. It forms a class of salts which greatly resemble the ace- 
tates ; they are all soluble, and are blackened by an excess of alkali even more 
readily than the acetates. 

Chloracetic acid exhibits a beautiful transformation when heated in contact 
with an alkali ; it is decomposed into perchloride of formyle, a metallic chloride, 
and alkaline carbonate and formiate. Acetic acid gives in the same cir- 
cumstances light carburetted hydrogen (C 2 HJ and an alkaline carbonate. 
(Dumas, An. de Ch. lxxiii, 77 and 89.) 

Heavy chlorinated ether. — The body which principally is formed when alco- 



538 ACETYL. 

hoi of 80 per cent. (0.848) is saturated with humid chlorine gas. It precipitates 
from the acid liquid when water is added. It is colourless, neutral, of density 
1 ,277, and boils between 112 and 125° cent. The results of its analysis are 
discordant, which M. Regnault supposes to arise from intermediate chlorinated 
bodies, which form between aldehyde and chloral : 

Aldehyde C 4 H 4 2 

C A H 3 C1 O 



Intermediate bodies. 
Chloral CJ 



C 4 H 2 C1 2 2 



Bromal, C^BrgO-f HO. — This compound whjch corresponds with chloral, 
was formed by M. Lee wig by adding 13.8 parts of bromine to 1 part of alcohol 
cooled by ice, adding the former in small portions,, taking care that the part 
previously added had first disappeared. It is purified in the same manner as 
chloral. Bromal is a colourless oily liquid of a peculiar and very strong odour 
which provokes tears, and of a caustic taste. Its density is 3.34, and boiling 
point below 212°. Bromal is miscible with water, alcohol and ether. Caustic 
alkalies transform it into an alkaline formiate and perbromide of formyl. Its so- 
lution affords by evaporation a crystalline hydrate, containing 4 atoms of water, 
consequently two atoms more than the hydrate of chloral. 

Brominated ether. — Lcewig has observed, that bromine in acting upon ether, 
produces a body analogous to heavy chlorinated ether, but respecting the com- 
position of which there is the same uncertainty. 

Iodal. — An oleaginous liquid which corresponded in some properties with 
chloral, was obtained by M. Aime, by the action of 4 parts of alcohol, one 
part of iodine, and one part of fuming nitric acid, left in contact in a bot- 
tle imperfectly closed ; but its composition was not ascertained. Mr. John- 
ston had previously obtained some peculiar substances by a similar reac- 
tion. 

Chloride of cyanogen upon alcohol. — A slightly volatile crystalline matter is 
produced, when a mixture of alcohol and very concentrated hydrocyanic acid, 
or a mixture of alcohol and a metallic cyanide soluble in alcohol, is saturated 
with dry chlorine. This crystalline substance has a silky lustre, and consider- 
ably resembles sulphate of quinine. It fuses at 248°, subliming in part. Its 
empyrical formula is C l6 H i4 8 CI 2 N 2 , corresponding with 3 atoms of aldehyde 
3 (C 4 H 4 2 ,) 2 atoms of chlorine- CI 2 ,~ 2 atoms of cyanogen N 2 C 4 , and 2 atoms 
of water H 2 2 . (Stenhouse.) 



SECTION y„ 



CONGENERS OF ALCOHOL OF AN UNCERTAIN CONSTITUTION. 

Hydruret of acetyl, olejiant gas, etherine, elayl (Berzelius;) C 4 H 4 =C 4 H, 3 
H or AcH. — This gas is generally prepared by heating a mixture of 1 part of 
alcohol with six or seven parts of concentrated sulphurous acid (page 304 ;) 
and is accompanied by sulphurous acid, the vapour of ether^ the double sulphate 
of oxide of ethyl and etherole (page 526,) from all of which it is purified by pas- 
sing it first through milk of lime, and then through oil of vitriol. M. Mitscher- 
lich finds it to be formed almost exclusively, when alcohol is brought into con- 
tact with oil of vitriol heated to 320 c (page 526.) 



OLEFIANT GAS. 539 

Pure hydruret of acetyl has a feeble ethereal odour ; it is only very slightly 
soluble in water, oil of vitriol, alcohol and ether. It forms a crystalline com- 
pound with anhydrous sulphuric acid, C 4 H 4 -f-4S0 3 . It combines with chlorine 
gas in equal volumes, and forms an oily liquid (a property from which it received 
the name of olefiant gas,) the chlorhydrate (hydrochlorate) of the chloride of 
acetyl, known as Dutch-liquid, or the oil of olefiant gas. 

Chlorhydrate of chloride of acetyl, C 4 H 3 C1,HC1 or AcCl,HCl. — Is purified 
by mixing with water and distilling the product last mentioned, by a water bath; 
depriving it afterwards of the water which it takes up by shaking it in a bottle 
with sulphuric acid, and distilling again by a water bath. It is a very fluid 
colourless liquid, of an agreeable ethereal odour and sweetish taste ; boils at 
82.4° cent. ; density of its vapour 3448.4. It communicates its odour to water 
without dissolving sensibly in it, but is soluble in all proportions in alcohol and 
ether. This compound may be distilled from hydrate of potash without change, 
but is gradually decomposed by an alcoholic solution of potash into chloride of 
potassium and chloride of acetyl; when this compound is heated with potas- 
sium, hydrogen gas and the chloride of acetyl are disengaged. 

Chlorhydrate of chloride of acetyl readily absorbs chlorine, and by the con- 
tinued action of that body a product is obtained, which by distillation furnishes 
two new compounds, one at 235° (115° cent.) C 4 H„C1 2 , HC1; and another at 
275° (135° cent.) C 4 H S CI 4 . The last compound by the continued action of 
chlorine in diffuse day-light, or more rapidly when exposed to the direct rays of 
the sun, is converted into the crystalline protochloride of carbon C v CI 6 (page 271.) 
Chloride of acetyl, C 4 H 3 Cl,=AcCl, separates from the alcoholic solution 
above referred to, in the form of gas, by the effect of a gentle heat ; the gas is 
purified from adhering vapours of alcohol and water, by passing it through sul- 
phuric acid. This gas has an odour which suggests that of garlic ; its density 
is 2166, and combining measure 4 volumes. It is condensed into a limpid 
liquid at 1.4° (-- 17° cent.) 

Chloride of acetyl is absorbed by perchloride of antimony (SbCl 5 ,)and when 
the saturated solution is diluted with water, an ethereal liquid separates, con- 
sisting of a mixture of chloride of acetyl and hydrochloric acid, with a new 
compound C 4 H 3 C1 3 , or C 4 H 2 C1 2 -J-HC1. This last when distilled with an 
alcoholic solution of potash is resolved into chloride of potassium, water and 
another new volatile liquid, C 4 H 2 C1 2 , or C 2 HC1. Lastly, by continuing the 
action of chlorine upon the preceding bodies, the compound C 4 H 2 C1 4 is obtained, 
or rather C 4 HCl 3 -fHCl, for potash transforms it into C 4 HC1 3 , and chloride of 
potassium. (Regnault.) 

Bromhydrate of bromide of acetyl, C 4 H,Br+HBr, is a colourless liquid, 
boiling at 129.5° cent., obtained by passing olefiant gas into bromine. 

Bromide of acetyl, C 4 H 3 Br=AcBr, a gaseous body of density 3691, of 
which the preparation is the same as that of chloride of acetyl. 

Iodhydrate of iodide of acetyl, C 4 H 3 I-f-HI. — This compound is slowly pro- 
duced when iodine is left in a bottle of olefiant gas at the ordinary temperature, 
and sublimes in white crystals ; but it is best prepared, according to Regnault, 
by heating iodine to 122 or 140° in a convenient vessel, and introducing pure 
olefiant gas into it, till all the iodine is converted into a pulverulent yellow or 
white substance. The compound fuses at 172.4° (78° cent..) and may be sub- 
limed in olefiant gas, but not in air without decomposition. When heated with 
hydrate of potash and alcohol, there is a disengagement of olefiant gas and 
formation of iodide of potassium, and other products which have not been 
studied. This body does not furnish products corresponding with those derived 
from the chlorhydrate of the chloride of acetyl, when decomposed ; it is very 
doubtful, therefore, whether the former is similar in constitution to the latter, as 
represented above. 

Chloroplatinate of chloride of acetyl, C 4 H 3 PtCl 2 =C ii H 3 Cl-f PtCl, or AcCl-f- 



540 ACETYL. 

PtCl. — This compound is formed by the action of bichloride of platinum upon 
alcohol, together with aldehyde, but it is best prepared from a double compound, 
which it forms with chloride of potassium or chloride of ammonium. Pure 
bichloride of platinum containing no free nitric acid is dissolved in alcohol ; a 
small quantity of free hydrochloric acid, and a quantity of chloride of potassium 
equal to one-eighth of the weight of the bichloride of platinum are added to this 
solution, and the whole digested for several hours at the temperature of boiling 
water. The excess of alcohol is removed by distillation, and the residue satu- 
rated with carbonate of potash. By evaporating at a gentle heat the compound 
in question is obtained in the crystalline form, and may be purified by new 
crystallizations. (Liebig's Traite.) By dissolving this compound in a little 
water and adding bichloride of platinum to the solution, so long as the double 
chloride of platinum and potassium precipitates, a yellow liquid is obtained, 
which ought to be evaporated in a dry vacuum in the absence of light. There 
results a gummy mass of a honey yellow colour, liable to be blackened by light, 
which is the chloroplatinate of the chloride of acetyl. It dissolves slowly in 
water and alcohol ; these solutions have an acid re-action. The hydrochloric 
acid of Dutch-liquid being represented by proto-chloride of platinum, PtCl, the 
compound described and Dutch-liquid may be considered as analogous: 

Chlorhydrate of chloride of acetyl. . . AcCl+HCl. 
Chloroplatinate of chloride of acetyl . . AcCl-f-PtCl. 

But various other views of the constitution of this compound have been 
proposed. 

Chloroplatinate of chloride of acetyl and potassium, AcCl,PtCl-fKCl. — The 
discovery of this salt, of which the preparation has just been described, is due 
to Berzelius. It crystallizes in semi-transparent regular prisms, of a lemon-yel- 
low colour, which abandon 4.625 per cent, of water of crystallization at 212° 
and become quite opaque. It is soluble in alcohol, and also in 5 parts of hot 
water, and is less soluble in cold water. The solution is partially decomposed 
when heated to 194°, metallic platinum being precipitated and hydrochloric acid 
liberated, which last protects the salt from further decomposition. 

Chloride of ammonium and chloride of sodium form corresponding double 
salts with the chloroplatinate of chloride of acetyl. 

Jlmmoniacal chloroplatinate of chloride of acetyl. — Ammonia or the car- 
bonate of ammonia throws down a lemon yellow precipitate from the solu- 
tion of these double compounds, in which the chloroplatinate of chloride of 
acetyl is united with the elements of one atom of ammonia: AcPtCl 2 + 
NH 3 . It is soluble in alcohol; sparingly soluble in cold water; and its 
solution cannot be evaporated without decomposition. 



SECTION VI. 



PRODUCTS OF THE ACTION OF HEAT UPON THE ACETIC ACID OF 

THE ACETATES. 

ACETONE. 

Syn. Pyroacetic spirit, mesitic alcohol, bihydrate of mesitylene (Kane.) 
Empyrical formula C 3 H 3 0. 

The vapour of strong acetic acid passed through a porcelain tube heated to 



ACETONE. 541 

dull redness is decomposed without the deposition of any charcoal, being con- 
verted entirely into the vapour of acetone, which condenses, and a mixture of 
gases, containing carbonic oxide, carbonic acid and carburetted hydrogen. If 
the temperature exceeds a dull red heat, the products are a brown empyreumatic 
oil, inflammable gases and a deposite of charcoal. Anhydrous acetic acid 
contains the elements of 1 atom of carbonic acid and 1 atom of acetone: 

C 4 H 3 3 = C0 2 and C 3 H 3 0. 

The acetates of the stronger bases which retain carbonic acid at a red heat, 
when submitted to destructive distillation become carbonates, and supply no 
volatile product except acetone. The acetates of earths of which the carbo- 
nates are decomposed at a red heat, such as magnesia, afford a mixture of ace- 
tone and carbonic acid, when distilled; and acetates of bases which are easily 
reduced, such as the acetates of copper and silver, yield hydrated acetic acid, 
carbonic oxide, carbonic acid water and acetone, the residuum containing a 
mixture of the metal and highly divided charcoal. Acetone also appears 
among the products of the distillation with an alkali of sugar and other ter- 
nary compounds of carbon, oxygen and hydrogen (page 486.) 

Acetone may be conveniently prepared by distilling a mixture of 2 parts of 
crystallized acetate of lead and 1 part of quicklime in a salt-glaze jar (gray- 
beard,) the lower part of the jar being coated with fire-clay, and a bent glass 
tube half an inch in diameter adapted to the mouth by a cork, so as to 
form a distillatory apparatus. The jar is supported in the mouth of a small 
furnace, by which the lower part of the jar only is heated to redness, and the 
vapours conducted into a Liebig's condenser. The product is redistilled from 
quicklime repeatedly, till its boiling point is constant at 132°. 

Acetone is a limpid colourless liquid, having a peculiar penetrating and 
slightly empyreumatic odour. Its density in the liquid state is almost the 
same as that of alcohol 0.7921, and the density of its vapour 2022, air being 
1000; its taste is disagreeable and analogous to that of peppermint. It is mis- 
cible in all proportions with water, alcohol and ether. Many salts which are 
soluble in alcohol and water are insoluble in acetone, particularly chloride of 
calcium and hydrate of potash; acetone is separated from water, by dissolving- 
such salts in the mixture of these liquids. Acetone is highly inflammable 
and burns with a white flame. 

On rectifying acetone derived from the acetates, a less volatile oleaginous 
body remains in the retort, which has been examined by Dr. Kane and 
named dumasine. This empyreumatic oil has a disagreeable odour and burn- 
ing taste; it boils at 248° (120° cent.): its composition is expressed by C 10 H 8 
O; the density of its vapour is, 5204, and its combining measure 4 volumes. 

Meta etone, C 6 H.O, which is also obtainable from sugar, has already 
been described, (page 512.) 

Dr. Kane who examined acetone and the products of its decomposition 
several years ago, then assigned to the former the constitution of an alcohol, 
doubling its atomic weight and giving it the formula: 

C 6 H 5 0+HO. 

The bodies derived from it, which I can only notice very snortly, were named 
by him on that theory. 

Mesifylene, C 6 H 4 . — This hydrocarbon is an oily colourless liquid, obtained 
on distilling acetone with half its volume of fuming sulphuric acid. It is ob- 
viously formed by the abstraction of the elements of 2 atoms of water from 
acetone. Sulphuric acid, nitric acid and chlorine react upon mesitylene in the 
46 



542 MESITYLENE. 

same way as they do upon benzin (benzole.) Mesitylene is lighter than 
water; it boils at 276.4° (135.5° cent.) Later in the distillation of the mate- 
rials which yield that oil, another oil which resembles it much passes over, 
but of which the boiling point is more elevated. The formula of the second 
oil appears to be C 6 H 3 . 

Oxide of mesityle, C 6 H 5 (Kane.) — Is obtained on adding caustic potash 
to the chloride of mesityle; a limpid colourless liquid, not miscible with water, 
having the odour of peppermint; it boils at 248°. 

Chloride of mesityle, C 6 H 5 C1 (Kane.) — Produced by the direct action of 
hydrochloric acid upon acetone, or by adding 2 parts of perchloride of phos- 
phorus gradually to 1 part of acetone. An oily liquid denser than water, and 
not miscible with that liquid. 

Chloroplatinate of oxide of mesityle, C 6 H 5 0,PtCl 2 (Zeise;) named metace- 
chlorplatin by Zeise. — Obtained by distilling a solution of 1 proportion of bi- 
chloride of platinum with 21 proportions of acetone, when hydrochloric acid 
and an ethereal body pass over into the receiver, and a brown acid residue is 
left in the retort. The residue contains a resinous matter which Zeise names 
the resin of platinum; the aqueous solution derived from washing the resin, 
becomes turbid after a time, and deposites the compound in question in small 
yellow crystals which lose nothing at 212°. It is slightly soluble in water; 
the solution is decomposed by ebullition. When the mother liquor of these 
crystals is distilled, there is a disengagement of gas, and a black flocculent 
powder is precipitated, which is explosive by heat. Zeise has named it py- 
racechlorplatin. 

Sidphomesitilic acid. — By the action of fuming sulphuric acid upon acetone 
there is produced among other products, an acid of which the salt of lime is 
expressed by: 

CaO,C 3 H 3 0-fS0 3 . 

This salt loses the elements of half an atom of water by heat. Its acid does 
not correspond with sulphovinic acid as the saturating power of the sulphuric 
acid in the former is not injured by the acetone, while it is diminished one- 
half by the oxide of ethyl in the latter. Nor can acetone be reproduced from 
sulpho-mesitylic acid by any means. Acetone likewise affords no peculiar 
acid by its oxidation, as alcohol does acetic acid. Hence acetone is deficient 
in what are now considered the three most essential characters of an alcohol. 

When 2 measures of acetone are mixed with 1 measure of hydrate of sul- 
phuric acid, and the liquid diluted with water and neutralized with lime, a 
new salt is obtained analogous to the former, but containing twice as much 
acetone: 

CaO,C c H c O,-fS0 3 . 

The acid of these salts undergoes decomposition when deprived of its base by 
sulphuric acid, and evaporated. 

By the action of nitric acid upon acetone Dr. Kane obtained the following 
two bodies, the composition of which, however, is somewhat doubtful: 

Nitrite of oxide of pteleyl . . . C 3 H 3 0-fNO s ; 
Mesitic aldehyde. ...... C 3 H 3 2 . 

By the action of phosphoric acid and of phosphorus with iodine, two acids 
were also obtained: phosphomesiiylic acid and hypophosphomesitylous acid, 
the formula of the salt of barytes of the latter being, BaO,C 6 H 6 3 P. 

Mesitic chloral, C 6 H 4 C1 2 2 (Dumas, Kane.) — Obtained by passing dry 
chlorine through acetone, till the disengagement of hydrochloric acid ceases. 



ARSENICAL COMPOUNDS FROM ACETYL. 543 

It is a liquid of a penetrating insupportable odour, insoluble in water; density 
1.33, and boiling point 258.8° (126° centig.) 

Chloride of pteleyl, C 3 H 3 C1 (Kane.)— A crystalline substance obtained by 
passing a current of chlorine into mesitylene. 



SECTION VII. 



ARSENICAL COMPOUNDS DERIVED FROM ACETYL. 

By the dry distillation of equal weights of acetate of potash and arsenious 
acid, a remarkable liquid is obtained, known as the liquor of Cadet or alcarsin. 
This liquid may be supposed to be formed by the abstraction of 2 atoms of 
carbonic acid from the elements of 2 atoms of acetone and 1 atom of arsenious 
acid: 

2 atoms acetone. . . C 6 H 6 2 

1 ,, arsenious acid. . *< As 3 

— 2 ,, carbonic acid. . C„ 4 



1 ,, alcarsin. . . C 4 H 6 As 

This is a body remarkable for its insupportable odour and spontaneous in- 
flammability in air. The mode of formation and oxidability of alcarsin, favour 
the idea that it belongs to the acetyl series and contains arsenietted hydrogen. 
In the following scheme of the composition of alcarsin and its derivatives, the 
former is represented as containing the hypothetical oxide of acetyl and ar- 
senietted hydrogen (Liebig:) 

Alcarsin. . . . AcO -f-AsH., 

Chlorarsin. . . . AcCl -f-AsH 3 

Sulpharsin. . . . AcS +AsH 3 

Cyanarsin. . . . AcCy-fAsH 3 

Alcargen. . . . Ac0 3 -f AsH 3 +HO. 

Berzelius, however, considering the pre-existence of arsenietted hydrogen 
in these compounds as improbable, presumed alcarsin to be the oxide of a 
compound radical, which he named ca icody i (from x*y.c; and cfrvc,,) in reference 
to the repulsive odour of alcarsin. The same theory is adopted by M. Bun- 
sen, who has devoted great labour and much ingenuity to the painful inves- 
tigation of this class of bodies, of which the sensible properties are most 
offensive and dangerous. M. Bunsen has succeeded also in isolating cacodyl, 
the supposed radical of the series, a discovery of much interest for the theory 
of compound radicals. 



CACODYL. 

Formula C 4 H 6 As=Kd. 

Cacodyl is a liquid obtained from the continued digestion of the chloride of 
cacodyl with metallic zinc at 230°, and dissolving out the chloride of zinc 
formed by water. It is dried by quicklime, distilled in a glass retort filled 
with carbonic acid to exclude air and crystallized repeatedly at 21.2° ( — 6° 
centig.) 



544 CACODYL. 

Cacodyl is an ethereal limpid liquid (greatly resembling its oxide,) of a nau- 
seous odour, which crystallizes in shining prisms at 23°. It takes fire spon- 
taneously in air and in chlorine gas, with the formation of a cloud of white 
smoke. It sinks in water, in which liquid it is insoluble; it is soluble in alco- 
hol and ether. Its boiling point is about 338° (170° cent.;) the density of its 
vapour by experiment 7101, by theory 7281; its combining measure 2 volumes. 
Its vapour is decomposed at a red heat into arsenic, olefiant gas and light car- 
buretted hydrogen. 

Oxide of cacodyl, alcarsin, C 4 H 6 As-f-0=KdO. — Is prepared by the dis- 
tillation of a mixture of equal weights of dry acetate of potash and arsenious 
acid. At the same time metallic arsenic distils over, with acetic acid and 
acetone which float in the receiver above the fluid alcarsin. The latter is 
obtained pure by washing with water free from air, and by distillation from 
quicklime in a retort filled with hydrogen gas, and from which atmospheric 
air is most carefully excluded. Oxide of cacodyl is also produced by the 
direct oxidation of cacodyl from slow access of air; and also from the partial 
reduction of cacodylic acid by phosphorous acid. 

Oxide of cacodyl is an ethereal limpid liquid, of very considerable refracting 
power, 1.762; it boils at about 302° (150° cent.) and solidifies in the form of 
white silky plates at — 9.4° ( — 23° cent.) Its odour suggests that of arseniet- 
ted hydrogen, is most disgusting, and provokes a copious flow of tears. The 
density of its vapour is 7555 by experiment, and 7833 by theory; its com- 
bining measure 2 volumes. It takes fire spontaneously in air and burns with 
a white flame and strong odour. Taken internally alcarsin is a violent 
poison. 

Oxide of cacodyl is but slightly soluble in water, but dissolves in all pro- 
portions in alcohol and ether. It dissolves in caustic potash colouring the latter 
brown ; dilute nitric acid dissolves it without disengagement of gas, but when 
heated decomposition occurs. Oxide of cacodyl dissolves phosphorus, sulphur 
and iodine ; the solution of the last is colourless and deposites crystals, which 
disappear again when an excess of iodine is added. It combines with the 
hydrate of sulphuric acid, forming thin needles which have an acid reaction and 
are deliquescent. Besides combining with acids, oxide of cacodyl combines 
also with salts. When its solution in alcohol is mixed with a solution of chloride 
of mercury, a white precipitate falls, soluble in hot water and crystallizing from 
it, which is a compound of 1 atom oxide of cacodyl, and 2 atoms chloride of 
mercury. This compound is inodorous. It yields with hydrochloric acid, 
chloride of mercury and chloride of cacodyl. Oxide of cacodyl forms a similar 
compound with bromide of mercury. It reduces the salts of the suboxide and 
oxide of mercury. 

Cacodylic acid, alcargen, HO,C 4 H 6 As0 3 =HO-f-Kd0 3 . — Cacodyl and its 
oxide left under water to the slow action of air, oxidate so as to become caco- 
dylic acid. The hydrated acid crystallizes in large colourless prisms, is inodo- 
rous, not poisonous, fusible, soluble in water and in alcohol. It is reduced to 
the state of chloride of cacodyl by chloride of zinc, and to the state of oxide of 
cacodyl by phosphorus acid. Alcargen has a feeble acid reaction ; it combines 
with the alkalies, giving rise to compounds which have the aspect of gum and 
are not obtained under regular forms. It dissolves in the hydrate of sulphuric 
acid without being modified ; is not attacked by anhydrous sulphuric acid, and 
is oxidated with difficulty by nitric acid and aqua regia. 

M. Bunsen adds one atom of oxygen to the formula for alcargen, but Liebig 
has shown that the formula as given above is more in accordance with Bunsen's 
analysis of alcargen than his own view. 

Sulphuret of cacodyl, C 4 H 6 As-fS = KdS, maybe obtained directly by 
uniting cacodyl with 1 atom of sulphur, or by the distillation of chloride of 



OXIDE OF CACODYL. 545 

cacodyl with sulphuret of potassium. This body is also a product of the de- 
composition of oxide of cacodyl by sulphuretted hydrogen gas. It is an ethereal 
liquid, of a highly disagreeable smell, which does not fume in air, is heavier than 
water and insoluble in that liquid. The density of its vapour is by experiment 
7810, by calculation 8390, its combining measure 2 volumes. It is resolved by 
hydrochloric acid, into sulphuretted hydrogen and chloride of cacodyl. 

Per sulphuret of cacodyl of the composition 2C 4 H 6 As-f-5S == 2Kd-f5S, is 
formed when sulphur is dissolved in the preceding compound or in cacodyl 
itself. It may be crystallized from ether in colourless prisms, which fuse at 
109.4° (43° cent.) A motoseleniuret of cacodyl, has also been formed. 

Chloride of cacodyl, C 4 H 6 As-r-Cl = Kd-f-Cl, is formed by the digestion of 
oxide of cacodyl in hydrochloric acid, or by the slow action of chlorine on 
cacodyl. It is a colourless ethereal liquid which does not fume in air, does not 
solidify at — 49° ( — 45°cent.,) and is converted a little above 212° into a colour- 
less vapour, which inflames in the air. Its odour is extremely penetrating and 
stupifying. The density of its vapour is by experiment 4560, by calculation 
4860 ; its combining measure 2 volumes. Chloride of cacodyl combines with 
metallic chlorides. 

Similar compounds of cacodyl with bromine, iodine, and fluorine have been 
formed. 

Oxichloride of cacodyl, KdO+SKdCl, is formed by treating the chloride with 
water, or by distilling it with hydrochloric acid. The density of its vapour is 
by experiment 5460, by calculation 5300 ; its combining measure 3 volumes. 
It is a liquid very like the oxide, boiling at 228.2° (109° cent.) A corresponding 
oxibromide of cacodyl and an oxyiodide of cacodyl have been formed. 

Cyanide of cacodyl, C 4 H 5 As4-NC 2 = KdCy, is produced by the distillation 
of concentrated hydrocyanic acid or of a solution of cyanide of mercury with 
oxide of cacodyl. It crystallizes in fine prisms of a diamond lustre, highly 
limpid, which emit a strong and insupportable odour. It is insoluble in water, 
fusible at 91.4° (33° cent.,) and crystallizable by cooling. Its density in the 
state of vapour is 4650 by experiment, and 4540 by calculation; its combining 
measure 2 volumes. The cyanide is the most poisonous of the compounds of 
cacodyl. 

It will be observed that oxide of cacodyl or alcarsin corresponds in compo- 
sition with alcohol, if As is supposed equivalent to O. 

Alcohol. . . C\H 5 04-HOorC\H 6 0., 

Alcarsin. . . C 4 H 5 'As+HO oi C 4 H 6 6 As 

But as alcarsin is the oxide of a radical cacodyl, C 4 H 6 As, pursuing the 
analogy, alcohol should be the oxide of a corresponding radical C 4 H 6 0. 
Chemists will wait with interest for the investigations of M. Bunsen, illustra- 
tive of this point. In the meantime a doubt may be entertained whether the 
arsenic in alcarsin replaces the oxygen of alcohol, or whether there is any 
• ■lose relation between these two compounds. Their primary binary, or mole- 
cular structure is possibly very different. In the ether constituent of alcohol 
we have probably 4C zincous or .positive, and 5H-f-0 chlorous. While in 
cacodyl, we have 4C-fAs zincous, and 6H chlorous; so that placing the zinc- 
ous constituent to the left (as usual) and the chlorous to the right, we have the 
molecular formula for cacodyl as follows: 

As 

Cacodyl is thus represented as an association of acetyl and arsenietted hydro- 
gen, forming together a compound radical, which is combined in alcarsin, with 
1 atom of oxygen and in alcargen with 3 atoms of oxygen. 

46* 



546 ETHYL AND AMMONIUM SERIES- 



SECTION VIII. 



ON THE RELATION BETWEEN THE ETHYL AND AMMONIUM SERIES. 

A remarkable and highly interesting parallelism exists between these two 
series of compounds, to which the attention of chemists was first directed by 
Dr. Kane. It will be observed that acetyl has the relation to ethyl, which 
amidogen has to ammonium, the more compound radical in both cases contain- 
ing 2 atoms more of hydrogen than the simpler. We may suppose the ethyl 
compounds to contain acetyl, as the ammonium compounds are supposed, on 
one view, to contain amidogen; and when thus resolved the analogy of many 
of the ethyl to ammonium compounds is very striking. The principal diffe- 
rence between the two series depends upon a chemical difference in the cha- 
racters of their radicals; acetyl being capable of forming acids, while amidogen 
does not possess that property. 

Expressing amidogen NH 2 by Ad, and acetyl C 4 H 3 by Ac, the following 
pairs of compounds from the two series will be found to correspond in compo- 
sition, differing only in the one containing acetyl while the other contains 
amidogen. (Liebig's Traite.) 



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ETHYL AND AMMONIUM SERIES. 547 

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550 VISCOUS FERMENTATIONS. 



SECTION IX. 



LATIC AND VISCOUS FERMENTATION. 

At a temperature between 86 and 104°, the saccharine juices of plants con- 
taining albumen or other azotized matter, undergo a species of fermentation, 
which is different from the vinous, combustible gases being evolved with car- 
bonic acid, and a gummy matter formed, having the composition of gum-ara- 
bic, which renders the liquid ropy and thick, and hence the application of the 
name viscous to this fermentation. On examining the liquid after effervescence 
ceases, it is found to contain no alcohol, but two new substances, in large 
quantity, namely mannite and lactic acid, which together contain the elements 
of dried grape sugar, minus 1 atom of oxygen: 

Mannite. . . . C 6 H 7 6 
Lactic acid. . . . C 6 H;j0 5 



C 12 R 1Z 11 

MM. Boutron and Fremy have lately observed that the formation of lactic 
acid precedes that of the other products, and that it may be produced alone, 
without the evolution of any gas or formation of mannite. Diastase and 
caseum after they have undergone a modification by a few days' exposure in 
a humid state, to air, are of all organic matters containing nitrogen the most 
efficient in determining the lactic fermentation. Air does not interfere by its 
elements, unless in transforming the animal matter into the lactic ferment. 
The membranes of the stomach of the dog and calf have no action, when well 
washed with cold water and fresh, on neutral substances, such as sugar and 
dextrin, but after being preserved for some time in water, they acquire then 
the property to transform such matters rapidly into lactic acid. These mem- 
branes sometimes produce another acid, differing from the lactic, of which the 
salt of lime is insoluble in alcohol, while the lactate of lime is readily soluble 
in that liquid. The substance of bladder after being exposed humid till it 
begins to decompose, also excites the lactic fermentation. 

Diastase after being exposed two or three days to humid air undergoes a 
modification, and acquire the property of transforming starch into lactic acid, 
making it pass probably through the intermediate state of dextrin. Hence malt, 
slightly moistened and exposed to air for two or three days, when afterwards 
pounded and placed in water kept at a temperature of from 68° to 77°, becomes 
warm, and after a few days, the liquid is found to contain much lactic acid, 
This is a pure lactic fermentation, without any production of mannite. But 
animal matters prepared in a similar manner often modify sugar quite differ- 
ently, very little lactic acid is formed but considerable quantities of mannite and 
the viscid matter. Frequently indeed the sugar is wholly changed into alcohol 
and carbonic acid. The albuminous ferments in different stages of decomposi- 
tion produce different fermentations. (Annales de Chimie, &c, 3 serie, ii, 257.) 



LACTIC ACID. 551 



LACTIC ACID. 

Formula of the acid combined with oxide of zinc : 

C 6 H 5 5 =L; ofthehydratedacidH0-fC 6 H 5 O 5 ==H0L,; of the sublimed 
acid C 6 H 4 4 . 

Other sources of lactic acid, are the whey of milk, in which it is formed while 
the latter becomes sour, human urine, and probably most other animal fluids, 
the juice of fermented cabbage or sour-crout, and the fermented extracts of rice 
and of nux-vomica, the spent ley of tanners, and the sour water of the starch 
manufacture, from which lactic acid has been prepared for sale. 

The process for lactic acid recommended by Boutron and Fremy consists in 
mixing 8 or 12 pints of milk, with a solution of 8 or 12 ounces of milk sugar in 
water, and leaving the liquid exposed to air in an open vessel for several days, 
between 68° and 77°. The liquid being now found very acid, is neutralized 
with bicarbonate of soda ; after twenty-four or thirty hours, being again acid, 
it is saturated, and the saturation repeated till all the milk sugar is converted 
into lactic acid. When it is supposed that the transformation is complete, the 
milk is boiled to coagulate the caseum ; and the liquid filtered and evaporated 
to a syrupy consistence, with caution at a moderate temperature. The product 
of the evaporation is taken up by alcohol at 100°, which dissolves the lactate of 
soda. Sulphuric acid added in proper quantity to the alcoholic solution, forms 
sulphate of soda, which precipitates, and the liquid yields by evaporation lactic 
acid nearly pure. To purify the acid, it may be converted into lactate of lime, 
which crystallizes immediately in tufts which are perfectly white. From this 
salt lactic acid may be again separated by means of sulphuric acid. Or, the 
original lactic acid may be saturated with any other base, and crystallized lac- 
tates obtained in a very short time. 

Concentrated to a maximum by evaporation, lactic acid is a thick, colourless, 
uncrystallizabie liquid, of density 1.215, without smell, and having a strong sour 
taste, which is scarcely sensible when the acid is dilute. It is soluble in water 
and alcohol. Lactic acid dissolves the phosphate of lime, a property which some 
acids, particularly the acetic, do not possess ; it coagulates milk when warmed. 
When heated to 482° (250° cent.,) it undergoes a decomposition, water and 
several other secondary products appearing, but the principal product being a 
white crystalline sublimate, of which the composition is C 6 H 4 4 ; that is, anhy- 
drous lactic acid minus 1 atom of water. 

This new acid may be purified by dissolving the sublimate in boiling alcohol, 
from which it precipitates on cooling, in the form of rhomboidal tables, of a 
brilliant whiteness, which have a weak sour taste, are fusible at 224.6° (107° 
cent.,) and sublime at 482° without alteration. These crystals are very slowly 
soluble in cold water, but dissolve easily in boiling water; the acid then assumes 
2 atoms of water and returns to the condition of hydrated lactic acid. 

In the lactates, the single atom of basic water only of the formula is replaced 
by a metallic oxide ; no acid lactates are known, but some bacic salts of zinc 
and the magnesian metals appear to exist, which have not been studied. They 
are all soluble in water ; lactate of zinc is the most sparingly soluble. 

Lactates. — No lactate of oxide of ethyl has been formed. The lactates of 
potash, soda and ammonia are deliquescent, and do not affect a regular form. 
The lactate otbarytes is similar. Lactate of lime exists to the extent of 2 or 3 
per cent, in nux-vomica. It crystallizes in colourless needles radiating from a 
centre, which contain 5 atoms of water of crystallization. Lactate of zinc is 
crystallized by the cooling of a boiling solution, in four-sided prisms, terminated 
by summits truncated obliquely; they contain 3 atoms of water. Alcohol pro- 



552 AMYL. 

duces in the aqueous solution a white precipitate of a basic salt, which dissolves 
in water and crystallizes ; it appears to contain 3 atoms of oxide of zinc. Lac- 
tate of magnesia crystallizes in small plates, containing 3 atoms of water ; it 
dissolves in 30 parts of cold water. The lactates of alumina, nickel, lead and 
mercury are very soluble in water, and do not crystallize in a regular form. 

Lactates of protoxide of iron, FeO,L-f-3HO, of oxide of copper, CuO,L+2HO, 
and of silver are crystallizable. 

Lactate of urea was discovered by MM. Cap and Henry in urine. It may be 
formed artificially by the double decomposition of lactate of lime and oxalate of 
urea, the oxalate of lime being separated by a filter, and the liquid evaporated 
by a gentle heat. The evaporation is terminated in vacuo near concentrated 
sulphuric acid. Lactate of urea crystallizes in colourless hexagonal needles, 
of a sharp and cooling taste, which are deliquescent. At a moderate heat it 
enters into fusion, and sublimes without alteration. Lactate of urea differs 
from the oxalate and nitrate of urea in not containing 1 atom of water of com- 
bination which these possess. 



SECTION X. 



OIL OF GRAIN-SPIRITS ORFOUSEL OIL, AND BODIES DERIVED 

FROM IT. 



AMYL SERIES OF COMPOUNDS. 

Amyl, C l0 H n =Ayl; the hypothetical radical of a series of compounds, of 
which the hydrate of the oxide has long been known as fousel oil, or as the oil 
of grain-spirits or potatoes, as it is produced in the fermentation of unmalted 
grain and potatoes, along with alcohol, and distils over with the latter. It has 
been studied very fully by M. Cahours (An. de Chim. &c. lxx. 81, and lxxv. 193.) 
There is every reason for considering this body as an alcohol, the most striking 
analogy existing between oil of potatoes and ordinary alcohol. This will be 
made sufficiently evident by the following table, in which the corresponding 
compounds of the ethylic and amilic series are compared : 



AMYL. 553 



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47 



554 AMYL. 



HYDRATE OF OXIDE OF AMYL, OIL OF POTATOES, AND OF GRAIN 

SPIRITS. 

Syn. Fousel oil, amilic alcohol, bihydrate of amylene; C ]0 H n O,HO 
(Dumas.) 

In distilling the fermented wash of grain or potato spirits, a milky liquid comes 
over towards the end of the process, and an oil subsides after a time, which is 
hydrate of oxide of amy], mixed with nearly an equal quantity of alcohol and 
water. To purify the crude product, it is agitated with water several times, 
left in contact with chloride of calcium for some time, and distilled again. The 
alcohol and water come off first, and the boiling point of the liquid rises to 
269°.6 (132° centig.,) when the receiver should be changed, as what then passes 
over is perfectly pure. 

Hydrate of oxide of amyl is a colourless, limpid, oily liquid, of which the 
odour, at first agreeable, soon becomes rank and nauseous. The inspiration of 
its vapour occasions spasmodic pains jn the chest, with coughing and even 
vomiting. It burns with a bluish white flame. Its taste is very acrid. It stains 
paper, but the stain disappears after a time. The density of this liquid is 0.8124 
at 59° ; its boiling point 269°. 6 ; the density of its vapour 3147, of which the com- 
bining measure contains 4 volumes ; it freezes at — 2 or — 4° in crystalline leaf- 
lets. Water dissolves a small quantity of it so as to acquire the odour of the 
oil ; it is miscible in all proportions with acetic acid, alcohol, ether, the fat and 
essential oils. It may be mixed also with solutions of caustic potash and soda ; 
when heated with hydrate of potash, hydrogen gas is given off, and the valerate 
of potash formed. When distilled with anhydrous phosphoric acid, it yields a 
liquid hydrocarbon, to which Cahours has given the name of amilene. 

Hydrate of oxide of amyl unites directly with bichloride of tin, according to 
Gerhardt, and forms a crystalline compound, which is decomposed by water. 

Chloride of amyl, C^Hj 1 ,Cl=AylCl. This compound is obtained by dis- 
tilling equal parts of oil of potatoes and perchloride of phosphorus. In a state 
of purity, it is a colourless liquid, of a pretty agreeable odour, insoluble in wa- 
ter, boiling about 2 15°. 6 (102° centig.,) perfectly neutral to test-paper, and 
having no action upon a solution of nitrate of silver. 

IT 

Chlorinated chloride of amyl, C x op1 3 CI. This substance is the ultimate pro- 

duct of the action of chlorine gas upon the oil in a bottle exposed to the sun, 
and is formed by the substitution of 8 atoms of chlorine for 8 atoms of hydro- 
gen. It is a colourless liquid, of a strong odour, suggesting that of cam- 
phor. 

Bromide and iodide of amyl were also formed by Cahours. Caustic alkalies 
dissolved in water attack them with difficulty, but the same bodies dissolved in 
alcohol decompose these ethers with much facility. The iodide of amyl is pro- 
duced by distilling at a gentle heat, a mixture of 8 parts of iodine, 15 parts of 
hydrate of oxide of amyl, and 1 part of phosphorus. The density of its vapour 
is 6675, and combining measure 4 volumes. 

Acid sulphate of oxide of amyl, sidphoamilic acid, is formed when the 
ba'rytes of the following salt is exactly precipitated by dilute sulphuric acid ; it 
may be evaporated to a syrupy consistence in air or in vacuo, and is some- 
times obtained in the form of very fine needles. Its solution is decomposed by 
heat. When neutralized with bases, it forms a class of salts, the sulphoamilates, 
which are all soluble in water. 

Sulphate of oxide of amyl and barytes, BaO.AylO,S 2 6 -f 3HO. This salt 



VALERIC ACID. 555 

is prepared by mixing equal parts of concentrated sulphuric acid and hydrate of 
oxide of amyl, and neutralizing with carbonate of barytes; sulphate of barytes 
precipitates, while sulphate of barytes and oxide of amyl remains in solution, and 
may be crystallized by evaporation after being purified by animal charcoal. It 
forms pearly crystalline leaflets, which are very soluble in water and in alcohol, 
but scarcely dissolve in ether. The crystals contain 3 atoms of water ; when 
dried at 212° they retain only 2 atoms; the dry salt is decomposed at 392° 
(200° centig.) Its solution is decomposed by boiling, with escape of hydrate 
of oxide of amyl. 

Sulphate of oxide of amyl and potash forms colourless needles or plates, 
grouped about a common centre, is very soluble in water and alcohol, and has 
a very bitter taste. 

Sulphate of oxide of amyl and lead crystallizes with 2 atoms of water. Its 
solution is decomposed by ebullition, like that of the salt of barytes. The salt 
of lime is similar in composition. 

Acetate of oxide of amyl, C l0 H l 1 0,C 4 H,0 3 =AylO,Ac0 3 . It is produced 
by distilling a mixture of 2 parts of acetate of potash, 1 part of hydrate of oxide 
of amy], and one part of concentrated sulphuric acid. It is a colourless liquid, 
of an aromatic and ethereal odour, lighter than water, boiling about 257° ; in- 
soluble in water, but soluble in alcohol, ether, oil of potatoes, etc. Placed in 
contact with an aqueous solution of potash, it is altered very slowly ; an alcoholic 
solution of the same base, on the contrary, alters it rapidly, an alkaline acetate 
is produced, and the oil is regenerated. The density of its vapour is 4475, and 
combining measure 4 volumes. 

TT 

Chlorinated acetate of oxide of amyl, C t 0( ~,, 9 O+C 4 H 3 O 5 . Thiscompound 

is formed when the acetate is saturated with chlorine gas at a temperature in- 
creasing to 212°. It is a colourless neutral liquid, insoluble in water; and cor- 
responds in composition with the chlorinated acetic ether of Malaguti. It is a 
liquid body, which becomes yellow, and is altered by a heat above 302°. When 
exposed again to chlorine gas in sunshine, this liquid absorbs the gas, and a crystal- 
line product is formed containing more chlorine, but which has not been analyzed. 

Valeric or valerianic acid, HO,C 10 H„O r Oil of potatoes becomes acid 
when kept in contact with air. M. Cahours has observed, that if platinum black 
be heated, and the oil be allowed to fall upon it drop by drop in no greater 
quantity than is imbibed, oxidation occurs, and an acid liquid volatilizes'which 
has all the properties of valerianic acid, the acid obtained by distillation of the 
root of valerian (Valeriana officinalis) with water. Two atoms of hydrogen in 
the oil are replaced by 2 atoms of oxygen. Oil of potatoes corresponds in this 
respect with alcohol and wood-spirit, which are converted in similar circum- 
stances, by the substitution of 2 atoms of oxygen for 2 atoms of hydrogen, into 
peculiar acids, the acetic and formic acids. But valerianic acid was first ob- 
tained from the oil by MM. Dumas and Stass, by distilling it with hydrate of 
potash. One part of the oil was covered in a retort by about 10 parts of a 
mixture of equal parts of hydrate of potash and quicklime ; and distilled by a 
metallic bath at about 392° (200° centig.;) hydrogen gas comes over, and 
valerate of potash is formed. The mass is neutralized by a slight excess of 
sulphuric acid, and distilled to separate the valeric acid. At the same time, a 
portion of hydrate of oxide of amyl comes over, accompanied by a liquid having 
the composition of a valeric aldehyde. 

Obtained from pure valerate of soda, mixed with a slight excess of phosphoric 
acid, valeric acid is a colourless oil, lighter .than water, and possessed of a per- 
sistent and characteristic odour which recals that of the root of valerian, with a 
sharp and acid taste. The protohydrate produces a white spot on the tongue ; 
its density is 0.937 at 61°. 7 (16°. 5 centig.;) it boils without change at about 



556 (ENANTHIC ETHER. 

347° (175° centig.;) it remains liquid at 5°. It inflames easily, and burns with 
a white and smoky flame. The density of the vapour of this hydrate is 3660 
by experiment, 3550 by theory ; its combining measure 4 volumes, in which 
respect it differs from acetic acid. Valeric acid, agrees, however, with that 
acid in forming a terhydrate, the condition in which valeric acid is always ob- 
tained when separated from its salts dissolved in water. Placed in contact 
with water, valeric acid dissolves a certain quantity of it ; the water on its part 
dissolves the acid considerably. 

Valerates. — These salts are in general soluble in water. The valerates of 
potash and barytes are not crystallizable. The valerate of silver is a heavy 
crystalline powder, of sparing solubility, which might be confounded, from its 
appearance, with the fulminate of the same metal. 

MM. Dumas and Stass formed two acids by the action of chlorine upon valeric 

IT 

acid, chlorovalerisic acid, C l0rl 6 O 3 -fHO, in which 3 atoms of hydrogen 

TT 

are replaced by 3 atoms of chlorine, and chlorovalerocic acid, C l0 pi 5 O 3 +HO, 

in which 4 atoms of hydrogen are replaced by 4 atoms of chlorine. — (An. de 
Chim. Ixxiii, 136.) 

Amilene, C l0 H l0 ; a liquid hydrocarbon, obtained by distilling hydrate of 
oxide of amyl repeatedly with anhydrous phosphoric acid. It is colourless, 
possesses a peculiar aromatic odour, is lighter than water, and contains no 
oxygen. It boils at 320°; the density of its vapour is 5061 by experiment, and 
4902 by calculation, its combining measure 2 volumes. 



SECTION XL 



ETHEREAL OIL OF WINES. 

The characteristic odour of wine by which it is distinguished from dilute 
alcohol, is due to a particular substance, possessing the properties of an essential 
oil. This is common to all wines, and is not to be confounded with the principle 
which is generally termed the flower, aroma or bouquet of individual wines, 
which is not volatile, and appears to be different in diverse kinds of wine and 
to be altogether wanting in many kinds. 

This oil is less volatile than alcohol, and a small quantity of it is found in the 
still after the distillation of a large quantity of wine. The same oily liquid is 
also obtained on distilling the lees of wine, especially what is deposited at the 
bottom of the tun after the fermentation has begun. It constitutes about -^q^-qo 
part of wines. This oil belongs to the class of compound ethers, and contains 
a new acid, which has been named o?nanUiic acid,* in combination with ether ; 
the oil, therefore, falls to be named oenanthic ether. 

CEnanthic ether, C 4 H 5 0,C 1 JH^Og. The crude ether contains a variable 
quantity of free acid in a state of mixture ; being more volatile than the acid, 
the oil may be separated from it by a simple distillation, collecting only the first 
fourth of the product. To obtain it perfectly pure, it is preferable to agitate 
the oil frequently with a hot solution of carbonate of soda, which dissolves the 
free acid without altering the ether. The small quantity of water and alcohol 
it retains may be withdrawn from it by digestion with chloride of calcium. 

The ether purified in this manner,' is very fluid, colourless with the odour of 

, — ■ . , t * , 

* From civ 05 wine, and «v8a? flower. 



(ENANTHIC ACID. 557 

wine extremely strong, and almost intoxicating when closely inspired. Its taste 
is very strong and disagreeable. It dissolves easily in ether and in alcohol, 
even when the latter is pretty dilute; water does not sensibly dissolve it. Its 
density is 0.862, its volatility very feeble ; it boils between 437 and 446° (225 
and 230° centig. ;) the density of its vapour is by experiment 10508, by calcu- 
lation 10476.9, its combining measure 2 volumes. (Enanthic ether is instantly 
decomposed by caustic alkalies, but is not sensibly affected by alkaline carbo- 
nates, nor by ammonia. When boiled with caustic potash, it disappears in a few 
seconds, a considerable quantity of alcohol distils over, and the liquor contains 
a compound of cenanthic acid and potash, which is very soluble in water. 

(Enanthic acid, HO,C |4 H 13 2 . When separated from its alkaline combi- 
nations, well washed with hot water and dried, this acid, at 55°.7, is of the con- 
sistence of butter and perfectly white, but at a higher temperature it melts and 
forms a colourless oil, without taste or odour, which reddens litmus, dissolves 
easily in caustic alkalies and in alkaline carbonates. It dissolves easily in alcohol 
and ether. This acid, like all the fatty acids, forms two series of salts, one acid 
in composition, without, however, manifesting a sensible acid re-action, the 
other neutral in composition, which exhibits a well-marked alkaline re-action. 

Hydrated cenanthic acid submitted to distillation abandons its water, and 
becomes anhydrous, C, i H l 3 2 , water and a little of the hydrated acid distilling 
over. The boiling point of the anhydrous acid is more elevated than that of 
the hydrated acid, as also is the point of fusion of the former; fused anhydrous 
osnanthic acid becoming solid about 87°. 8 (31° centig.) 

(Enanthic ether may be reproduced by means of the isolated cenanthic acid. 
When 5 parts of sulphovinate of potash are heated with 1 part of hydrated 
oenanthic acid, the mixture fuses; and if it is heated to 302° (150° centig.,) an 
oily liquid is seen to form on its surface, which is a mixture of oenanthic ether 
and cenanthic acid still free. If this oily layer be separated and heated with a 
solution of carbonate of soda, the free acid is dissolved and the ether remains 
in a state of purity. 



CHAPTER III. 



PRODUCTS OF THE DRY DISTILLATION OF WOOD. 

The principal products of the destructive distillation of wood at a red heat, 
are the charcoal which remains in the retort, gaseous compound of carbon, a 
watery fluid containing acetic acid, and a black odorous oily mass, known as 
tar. The last two products are highly variable mixtures of a great many sub- 
stances, of which the one that demands our first attention is pyroxylic spirit, or 
wood spirit. 



47* 



558 METHYL. 



SECTION I. 



METHYL SERIES OF COMPOUNDS. 

Formula of methyl, C 2 H 3 = Me. 

A volatile combustible spirit, soluble in water, was first obtained from the 
dry distillation of wood by Mr. P. Taylor. The composition and chemical 
nature of this spirit and of the compounds it forms, with their extraordinary 
parallelism to alcohol and the compounds derived from alcohol, were ascer- 
tained by MM. Dumas and Peligot, and published in their important memoir 
on wood-spirit (An. de Ch. lviii, 5.) Wood-spirit is the alcohol of a particu- 
lar series of compounds, being the hydrated oxide of a new radical methyl, 
which resembles ethyl perfectly in its functions, but differs in its composi- 
tion, containing 2 atoms less of carbon and 2 atoms less of hydrogen. The 
oxide of methyl is a base like the oxide of ethyl or ether, and forms acid and 
neutral salts like the latter. By the abstraction of 2 atoms of hydrogen from 
methyl, another radical formyi is produced, as acetyl is derived from ethyl, 
and having an acid oxide formic acid, corresponding with acetic acid. Me- 
thyl has not been isolated. 



OXIDE OF METHYL. 



Formula C2H3O = MeO. 

Syn. Methylic ether. — This compound is prepared by distilling wood- 
spirit with 4 parts of sulphuric acid, and transmitting the gas which comes 
over, first through a bottle containing milk of lime and afterwards through 
several bottles filled with pure water. The latter dissolves the oxide of methyl; 
the gas is evolved on boiling its solution, and must be collected over mercury. 
Oxide of methyl is a colourless gas of an agreeable ethereal odour, not 
liquefied by a cold of -f- 3°. 2 ( — 16° cent.,) and combustible; water dissolves 
37 volumes of this gas, alcohol, hydrate of oxide of methyl and concentrated 
sulphuric acid much larger proportions. It separates from the latter, on dilu- 
tion with water; the density of the gas is by experiment 1605, by calcula- 
tion 1570, and its combining measure 2 volumes. 

Oxide of methyl combines directly with the vapour of anhydrous sulphuric 
acid, in a glass balloon carefully cooled, and forms the neutral sulphate of 
oxide of methyl (Regnault.) 



HYDRATE OF OXIDE OF METHYL, OR WOOD-SPIRIT. 

Formula, C 2 H 3 0-f HO = MeO+HO. 

Syn. Pyroxylic spirit. — In the process of purifying the vinegar from wood, 
the crude acid is saturated with lime and concentrated by evaporation. The 
first portion of liquid which distils over contains the wood-spirit, which is 
concentrated by repeated rectification. The wood-spirit or pyroxylic spirit 
of commerce is a heterogeneous mixture, containing besides the hydrate of 
oxide of methyl which forms the larger part of it, acetone and several other 
combustible liquids. To purify the wood-spirit it is poured over an excess of 
chloride of calcium in a retort, and distilled by a water-bath heat, which ex- 



CHLORIDE OF METHYL. 559 

pels acetone and other liquids and leaves the wood-spirit united with the 
chloride of calcium. A measure of water equal to the original volume of the 
wood-spirit is then added to the retort, and the distillation continued; the 
latter liquid comes over diluted with a small quantity of water, from which it 
may be separated and obtained anhydrous by another distillation from quick- 
lime. 

Wood-spirit is a volatile colourless liquid, of an alcoholic but at the same 
time empyreumatic smell and taste. It is very inflammable and burns with a 
pale flame like alcohol. It is neutral, mixes when pure with water, without 
becoming turbid, and is also miscible with alcohol and ether. Its density is 
0.798 at 68°; it boils at 140° according to Kane, and at 151°.7 (66°.5 cent.) 
according to Dumas. The density of its vapour is by experiment 1120, by 
calculation 1110; its combining measure 4 volumes. 

Hydrate of oxide of methyl dissolves, with the acid of heat, small portions of 
sulphur and phosphorus; it dissolves also many resins, and is used in making 
spirit varnishes, and mixes with most volatile oils; its solvent power is indeed 
very similar to that of alcohol. Wood-spirit is acted upon by chlorine, per- 
oxide of manganese and sulphuric acid and by other oxidating agents, like 
alcohol, yielding analogous products. It is also decomposed by potassium, 
with disengagement of pure hydrogen. 

Anhydrous baryles is dissolved by pure wood spirit with evolution of much 
heat although not dissolved by alcohol, and a compound formed MeO,HO -f- BaO, 
which crystallizes in needles of a silky lustre. Wood spirit likewise dissolves 
lime. 

Chloride of calcium dissolves in wood spirit and crystallizes from a strong 
solution in large hexagonal tables, which deliquesce in air; they contain 2 atoms 
of hydrate of oxide of methyl united with 1 atom of chloride of calcium. Dr. 
Kane recommends the decomposition of this salt by heat as the best source of 
pure wood spirit. 

Chloride of methyl C 2 H 3 ,Cl=MeCl. — This compound is produced by the 
reaction of hydrochloric acid and hydrate of oxide of methyl upon each 
other. 

MeO-f HO and ClH=MeCl and 2HO. 

But it is best obtained, as are all the halogen compounds of mythel, by distilling 
neutral sulphate of oxide of methyl with a metallic salt of the proper salt radi- 
cal, or better a mixture of sulphuric acid, hydrate of oxide of methyl and the 
metallic salt. The salt used in the present case is chloride of sodium. Chloride 
of methyl is a colourless gas of an ethereal odour and sweet taste, of which the 
density is 1737.8 by experiment, and 1729 by calculation; the combining mea- 
sure is 4 volumes. Water dissolves 2.8 volumes of this gas at 60°. 8 (16° cen- 
tig.;) it is not liquefied by a cold of — 0.4° ( — 18° centig.) It will be remarked 
that the chloride and oxide of methyl are both considerably more volatile than 
the chloride and oxide of ethyl. 

Iodide of methyl, Mel; a colourless liquid, which burns with difficulty, boiling 
between 104° and 122° ; its density is 2.237 at 69.8° (21° centig.) 

Fluoride of methyl, MeF; obtained by distilling sulphate of oxide of methyl 
with fluoride of potassium ; a colourless gas, of which the density is 1186 ; wa- 
ter dissolves 1.5 volumes of it. 

Cyanide of methyl, MeCy ; an ethereal liquid, insoluble in water. 

Sulphuret of methyl, MeS; a very limpid liquid of which the odour is ex- 
tremely disagreeable. Its density is 0.845 at 69°. 8, and its boiling point 105°.8 
(41° centig.) The density of* its vapour is by experiment 2115, by theory 



560 METHYL. 

2158 ; its combining measure 2 volumes. Sulphuret of methyl is formed, when 
chloride of methyl is transmitted through an alcoholic solution of protosulphuret 
of potassium, by double decomposition. 

Sulphydrate of sulphuret of methyl or methylic mercaptan is obtained as a 
colourless liquid, lighter than water, which boils at 69°.8 and acts^upon oxides 
of mercury and lead like sulphydrate of sulphuret of ethyl (Gregory.) 



OXYGEN SALTS OF METHYL. 

The salts of oxide of methyl correspond so closely with those of ethyl that 
knowing the history of one class it is easy to predict the properties of the other. 
Anhydrous metallic oxides do not alter them, while the hydrated alkalies disen- 
gage hydrate of oxide of methyl from them with great facility. 

Neutral sulphate of oxide of methyl, MeOjSO^. — This member of the methyl 
series, which has no analogue in the ethyl series, is formed when oxide of me- 
thyl and anhydrous sulphuric acid are brought into contact. It constantly ap- 
pears also when hydrate of oxide of methyl is distilled with sulphuric acid, and 
in larger quantity the greater the proportion of sulphuric acid employed. To 
prepare sulphate of methyl it is convenient to distil 1 part of hydrate of oxide 
of methyl with 8 or 10 parts of sulphuric acid. When purified by washing with 
water, and two successive distillations with chloride of calcium and quick-lime, 
sulphate of methyl is a colourless liquid of an alliaceous odour, of density 1.324 
at 71°.6 (22° centig.,) which boils at 370°.4 (188° centig.,) and may be dis- 
tilled without change. The density of its vapour is 4363.4; it is composed $of 
equal volumes of anhydrous sulphuric acid and oxide of methyl condensed into 
one volume, so that its combining measure is the same as that of oxide of me- 
thyl or 4 volumes. It is decomposed very slowly by cold water, but rapidly by 
hot water, the acid sulphate of oxide of methyl and water being formed and 
oxide of methyl liberated. This compound may be employed in preparing 
all the other compounds of methyl, which are derived from it by double de- 
composition. 

Jicid sulphate of oxide of methyl, bisulphaie of oxide of methyl, sulpho- 
methylic acid ; HO.MeO-j-S.jO^. — This compound, discovered at the same time 
by MM. Dumas and Peligot and by Dr. Kane, is formed when concentrated 
sulphuric acid is mixed with hydrate of oxide of methyl, and also on dissolving 
the neutral sulphate in boiling water. Obtained by the last method and concen- 
trated by evaporation it is a colourless, syrupy, very acid liquid which in dry 
air becomes a mass of white crystalline needles. It combines with bases form- 
ing double salts, in which the basic water of the acid is replaced by a metallic 
oxide. All these salts are soluble in water. The double salt of oxide of ammo- 
nium, and oxide of ethyl has not yet been obtained. 

Sulphate of oxide of methyl and potash, MeO.KO,S 2 O e -fHO crystallizes in 
rhomboidal tables, which have the lustre of mother of pearl and deliquesce in 
damp air. Dr. Gregory has obtained two double salts by dissolving the present 
salt in a saturated solution of ferrocyanide of potassium, and evaporating ; the 
first which crystallizes yellow and insoluble in alcohol, is a compound of ferro- 
cyanide of potassium and ferrocyanide of methyl ; the second a white salt soluble 
in alcohol is a compound of sulphate of oxide of methyl and potash, bisulphate 
of potash and cyanide of methyl. 

Sulphate of oxide of methyl and barytes, MeO.BaO,S 2 6 -f 2HO ; is prepared 
by mixing equal parts of concentrated sulphuric acid and hydrate of oxide of 
methyl, and heating the mixture to its boiling point. After cooling the liquid is 
diluted and saturated first with carbonate of barytes and afterwards with hy- 
drate of barytes ; the excess of the latter is removed by a stream of carbonic 



OXYGEN SALTS OF METHYL. 561 

acid gas, and the liquid evaporated to its crystallizing point by a gentle heat. 
The salt crystallizes in colourless tables of a square base or in thin transparent 
plates, which effloresce in air and may be made anhydrous in vacuo. 

Sulphate of oxide of methyl and lead, PbO.MeO,S 2 6 +HO, is deliquescent. 
It has likewise been obtained with 2 atoms of water of crystallization and the 
same form as the preceding salt of barytes (Kane.) 

Nitrate of oxide of methyl, MeO,N0 5 . — The action of nitric acid upon wood spi- 
rit is different and much less violent than the action of the same acid upon alcohol. 
No nitrate of oxide of ethyl is formed, indeed such a compound does not appear 
to exist, while the nitrate of oxide of methyl is very easily obtained. One part 
of nitrate of potash and a mixture of 2 parts of concentrated sulphuric acid with 
1 part of wood spirit are introduced into a retort ; the mass rises greatly in 
temperature, and the product distils over without the necessity for applying arti- 
ficial heat ; it must be received in a very cold condenser. The heavier of the 
two liquids found in the receiver is nitrate of oxide of methyl contaminated 
with a portion of a very volatile compound supposed to be formiate of oxide of 
methyl, which communicates to the former the odour of hydrocyanic acid. 
The product is rectified from chloride of calcium and from litharge ; the last 
portions which distil over are perfectly pure. Nitrate of oxide of methyl is a 
colourless liquid of a weak ethereal odour, which inflames with facility and burns 
with a yellow flame; its density is 1.822 at 71°6. (22° centig.,) and boiling 
point 150°. 8 (66° centig.) Its vapour heated above 248° is decomposed with a 
violent detonation, producing carbonic acid, water and deutoxide of nitrogen. 
This ether is soluble in water, and miscible in all proportions with alcohol, ether 
and wood spirit. 

Neutral carbonate of oxide of methyl is unknown ; the double, carbonates 
which it forms with alkaline carbonates were prepared in the same manner as 
the corresponding double salts of ethyl. 

Oxalate of oxide of methyl, MeO,C 2 O v is a white solid transparent and 
brilliant mass composed of rhomboidal tables ; it fuses at 123°. 8 (51° centig.,) 
and boils about 321°.8 (161° centig.) It is decomposed by water and resolved 
into hydrated oxalic acid and wood spirit. Acid oxalate of oxide of methyl has 
not yet been obtained. 

Oxalate of oxide of methyl and oxamide or oxamethylane is formed when 
oxalate of oxide of methyl is exposed to dry ammonia. 

Sulphocarbonate of oxide of methyl and potash, KO.MeO,C 3 S 4 . 

Bicaanur ate of oxide of methyl, 3MeO,Cy 6 6 +6HO, (Richardson.) 

Benzoate of oxide ofmethyl,'C^H^O,C , 4 H 5 3 =MeO,BzO. 

Acetate of oxide of methyl, C 2 H 3 0,C 4 H 3 3 =:MeO,Ac03. 

Mucateof oxide of methyl, 2C 2 H 3 0,C 12 H ]4 7 =2MeO + Mu, (Mala- 
guti.) 



COMPOUNDS OF OXIDE OF METHYL OF AN UNCERTAIN 
CONSTITUTION. 

Oxichlorocarbonate of oxide of methyl, C 4 H' 3 I C10 A \ considered by MM. 
Dumas and Peligot as a compound of oxide of methyl, and a particular acid, 
and represented by the formula: 

C 2 H 3 0+C 2 ^. 

Urethylane, a body corresponding with urethane and formed in similar cir- 
cumstances. 



562 FORMYL. 

Sulphate of oxide of methyl and sidphamide, or sulphamethylane, C 2 H,0, 
S0 3 + NH 2 ,S0 2 . 



PRODUCTS OF THE DECOMPOSITION OF METHYL AND ITS 
DERIVATIVES. 

A compound belonging to the methyl series was obtained by MM. Dumas 
and Peligot, which appears to correspond with isethionic acid, by bringing 
anhydrous sulphuric acid in contact with hydrate of oxide of methyl, observing 
to keep the mixture cool. lis salt of barytes is crystallizable and has the same 
composition as sulphate of oxide of methyl and barytes, but does not agree 
with the latter in its chemical properties, and is evidently a different sub- 
stance. 

Under the influence of air, hydrate of oxide of methyl in contact with pla- 
tinum black undergoes oxidation, and forms an acid, which is found to be 
pure formic acid. In this conversion, 2 atoms of hydrogen combine with 
oxygen and form water, and 2 atoms of oxygen are absorbed at the same time, 
and combine with the remaining elements of the methyl, exactly as in the 
conversion of alcohol into acetic acid: 

C 2 H 3 + HO and 40=C 2 H0 3 + 3HO. 

Formic acid, therefore, contains a radical, which is named formyl, and to 
which it has the same relation as acetic acid has to acetyl: 

Acetic acid. . . . C 4 H 3 + 3 . 
Formic acid. . . . C 2 H +0 3 . 

Formyl, therefore, differs from methyl in containing 2 atoms less of hydro- 
gen, and as ethyl may be viewed as a compound of acetyl+2 atoms of hydro- 
gen, so methyl may be viewed as a compound of formyl -f 2 atoms of hy- 
drogen. 



SECTION II. 

FORMYL SERIES OF COMPOUNDS. 

Formyl, C 2 H=Fo. 

The series of formyl is less numerous than that of acetyl. The compounds 
of the former corresponding to aldehyde and aldehydic acid are deficient , 
formic acid being the only known oxide of formyl. 

The following are the derivatives of formyl: 



C 2 HO. . . 
C 2 HO + HO. 
C 2 H0 3 . . . 



C 2 H0 3 +HO. 
C 2 HC1 3 . . 
C 2 HBr 3 . . 
C 2 HI 3 . . 



Oxide of formyl (unknown.) 

Substance contained in formomethylal. 

Anhydrous formic acid. 

Hydrated formic acid. 

Perchloride of formyl (chloroform.) 

Perbromide of formyl. 

Periodide of formyl. 



FORMIC ACID. 563 



COMPOUND OF HYDRATE OF OXIDE OF FORMYL WITH OXIDE OF 
METHYL, OR METHYLAL. 

Syn. Formomethylal (Kane) C 6 H 8 4 (Malaguti.) 

By distilling 2 parts of wood spirit with 3 parts of sulphuric acid diluted 
with 3 parts of water, and 2 parts of peroxide of manganese, Dr. Kane ob- 
tained a substance mixed with several other bodies, which he named formo- 
methylal. It was considered a tribasic formiate of oxide of methyl, but was 
afterwards shown by Malaguti, to be a mixture of formiate of oxide of methyl 
and a particular substance which he named methylal. To purify the methylal 
from formiate of oxide of methyl, the latter must be decomposed entirely by 
hydrate of potash. 

Methylal is an ethereal colourless liquid of a very agreeable aromatic odour; 
it is miscible with 3 parts of water, and may be separated from that liquid by 
chloride of calcium or hydrate of potash. It is very inflammable, and burns 
with a white flame. The density of methylal is 0.8551; its boiling point 
107.6° (42° centig.;) its combining measure contains 4 volumes. Methylal 
may be represented as a compound of 1 atom of hydrate of oxide of formyl 
with 2 atoms of oxide of methyl = C 2 HO,HO-f 2C 2 H,0. M. Regnault 
has explained its formation by supposing that 3 atoms of oxide of methyl, 
formed by the action of sulphuric acid upon hydrate of oxide of methyl, 
group together so as to form a single molecule = C c H n 3 ; the last exposed 
to the oxidating action of peroxide of manganese loses 1 atom of hydrogen, 
which is replaced by 1 atom of oxygen, and consequently the compound C 6 
H 3 4 is produced. The formation of acetal which corresponds with methylal 
in the acetyl series is explained by Regnault in the same manner. 



FORMIC ACID. 

Formula HO +C 2 HO 3 = HO,Fo0 3 .— The relation of this acid to wood 
spirit has already been explained. It was distinguished as a particular acid by 
Gehlen, who found it in red ants (formica rufa;} and was first formed artifi- 
cially by Dcsbereiner, by distilling tartaric acid with sulphuric acid and per- 
oxide of manganese. All other vegetable substance when oxidized in the 
same manner, or by distillation with nitric acid, hyperiodic, iodic and hy- 
permanganic acids, or with a mixture of chromic and sulphuric acids, yield 
formic acid, carbonic acid and occasionally some acetic acid. 

To obtain the protohydrate in a state of purity, formiate of lead well pul- 
verized contained in a long glass tube is decomposed by a current of dry sul- 
phuretted hydrogen gas; and the disengaged formic acid afterwards distilled 
over by the application of a gentle heat. This hydrate is a colourless liquid, 
slightly fuming and possessing a pungent and peculiar odour. It crystallizes 
below 32° in brilliant plates; it boils at 212°; its density is 1.2353. 'The va- 
pour of the boiling acid is inflammable and burns with a blue flame; this hy- 
drate combines with a second atom of water forming a definite compound of 
which the boiling point is 222.8° (106° centig.,) which does not freeze at 5°, 
and of which the density is only 1.1104 at 59°. Both of these hydrates are 
highly corrosive. 

To prepare the dilute acid, a capacious glass retort or copper still is em- 
ployed, of which the capacity must be at least 10 times greater than the volume 
of the materials to be employed, namely 1 part of starch, 4 parts of peroxide 



564 FORMYL. 

of manganese, 4 parts of water, and 4 parts of sulphuric acid. The materials 
without the acid are first introduced into the retort and heated to 104° (40° 
centig.,) and then the sulphuric acid is added by small portions. A violent 
effervescence with swelling up of the materials occurs, from the disengage- 
ment of carbonic acid gas; when this ceases and all the acid is added, the 
capital is applied to the still, and the distillation continued, for which a heat a 
few degrees above 212° is sufficient, till 4| parts of the liquid are found in the 
receiver. The product is a dilute acid, of which the density is about 1.025; 
the last portions often contain sulphurous acid, and the product has always an 
aromatic odour from the presence of a small quantity of a volatile oil formed 
in the process. The nature of the decomposition which yields formic acid 
has not been exactly traced. To purify the crude formic acid it is neutra- 
lized by milk of lime, which forms an insoluble compound with sulphurous 
acid; the excess of lime is precipitated by a stream of carbonic acid and the 
formiate of lime evaporated to dryness. By distilling 10 parts of formiate of lime 
with 8 parts of oil of vitriol diluted with 4 parts of water, 9 parts of a pure 
acid are obtained of specific gravity 1.075. 

Formic acid is entirely decomposed by an excess of sulphuric acid, without 
being charred, being resolved into carbonic oxide which comes off with lively 
effervescence, and water which remains in combination with the sulphuric 
acid. The acid in question may easily be recognised by that property and 
also by its action upon the oxides of silver and mercury. When heated upon 
these oxides formic acid is completely destroyed, producing carbonic acid gas 
which is disengaged, water and metallic silver or mercury, without leaving 
the smallest trace of a salt of silver or mercury in the liquor. When the 
formic acid contains acetic aci'd, acetate of suboxide of mercury remains in 
solution. Heated with a solution of corrosive sublimate, formic acid reduces 
the latter to the condition of calomel, disengaging hydrochloric and carbonic 
acids; upon the salts of oxides of mercury and silver, formic acid has the 
same action as upon the oxides themselves. Metallic peroxides are reduced 
by it with the aid of heat to the state of protoxides, which combine with 
formic acid, while carbonic acid gas is disengaged. 

Formiates. — Formic acid is more powerful than acetic acid; the salts of 
both acids are all soluble in water. Formiate of soda is not soluble in alcohol 
like acetate of soda; the formiates comport themselves like the free acid, with 
sulphuric acid; they also when heated in excess with solutions of salts of silver, 
mercury, platinum or chloride of gold, precipitate these metals, producing a 
brisk effervescence. The salts of peroxide of iron are coloured deep orange 
by a formiate. 

Formiate of ammonia, NH A 0,Fo0 3 , crystallizes in square four-sided 
prisms; it is very soluble in water. This salt contains the elements of 1 
atom of hydrocyanic acid and 4 atoms of water: 

NH 4 0,C 2 H0 3 =H,NC 2 and 4HO. 

It is accordingly converted into these two products when its vapour is carried 
through a tube at a red heat. 

Formiate of oxide of ethyl, formic ether, EO,Fo0 3 . — This ether is obtained 
by distilling 7 parts of dry formiate of soda with a mixture of 10 parts of sul- 
phuric acid and 6 parts of alcohol of 90 per cent. It is a limpid liquid of an 
aromatic penetrating odour and cooling spicy taste. Its density is 0.912; its 
boiling point 128.12° (53.4° centig.) Formic ether dissolves in 10 parts of 
water; ammoniacal gas has no action upon it, while solution of ammonia de- 
composes it like the other alkalies. 



FORMIATES. 565 

Formiate of oxide of methyl is lighter than water, and boils between 36 
and 38° centigrade; its odour suggests that of acetic ether. 

Formiate of potash is very soluble and crystallizes with difficulty. For- 
miate of soda crystallizes in prisms of a rhombic base or in tables, containing 
2 atoms of water; it is very soluble and deliquescent in damp air. This salt 
is very suitable for reducing many metallic oxides, when heated with them to 
redness in the dry way, or when boiled with their solutions. Its solution may 
be employed to separate the reducible metals from iron, copper, manganese, 
&c, which are not deoxidized by formic acid. 

Formiate of barytes crystallizes in brilliant transparent prisms, which are 
persistent in air, soluble in 4 parts of water and insoluble in alcohol. For- 
miate of strontian crystallizes in transparent six-sided prisms, containing 4 
atoms of water. Formiate of lime is soluble in 10 parts of water, and scarcely 
more soluble with heat than in the cold, so that the best mode of crystallizing 
it, consists in evaporating its solution by a gentle heat. A concentrated solu- 
tion of the salt deposites, by evaporation, needles of a brilliant lustre, which 
effloresce when heated. Formiate of magnesia crystallizes in thin brilliant 
needles, persistent in air, which are soluble in 13 parts of water and insoluble 
in alcohol. Formiate of alumina gives by evaporation a gummy mass which 
is not crystalline. Its solution with the addition of sulphate of potash, alum, 
&c, becomes turbid when heated, like acetate of alumina. Formiates of man- 
ganese, protoxide of iron, zinc, cadmium, nickel, cobalt, and copper are very 
soluble and crystallizable salts. 

Formiate of cerium is a white granular and crystalline powder; it is the 
most insoluble formiate, a property of which advantage is taken in preparing 
pure oxide of cerium from solutions containing oxide of iron, lime and other 
oxides. At 392° (200° centig.,) this formiate enters into a kind of ebullition 
and is converted into carbonate of cerium, without charring. 

Formiate of lead requires 36 or 40 parts of water for solution, and preci- 
pitates when formic acid is added to a saturated solution of acetate of lead, in 
brilliant needles diverging from a common centre. The solution of formiate 
of lead has a sweet taste, it is capable of dissolving oxide of lead when boiled 
upon that oxide and acquires an alkaline reaction. Formiate of lead is inso- 
luble in alcohol. 

Formiates of suboxide and oxide of mercury. — Red oxide of mercury well 
pounded dissolves in formic acid, at the ordinary temperature and forms a so- 
lid crystalline mass on evaporating in dry air, which is the formiate of that 
oxide. On applying the slightest heat to this salt either dry or in solution, 
effervescence occurs from the escape of carbonic acid, and formiate of sub- 
oxide of mercury is produced. The latter salt is deposited from a solution 
so decomposed, in a crystalline very brilliant micaceous mass, which is com- 
posed of small plates of 4 or 6 sides, of a silky or silvery lustre. By a higher 
temperature formiate of the suboxide is decomposed whether dry or in solu- 
tion, with a slight explosion, metallic mercury being liberated with formic and 
carbonic acids. The decomposition of this salt is thus represented by Liebig: 
2 atoms of formiate of suboxide of mercury are resolved by heat into: 



2 atoms of carbonic acid. . . C 2 O t 
1 atom of hydrate of formic acid. . C 2 H 2 4 
4 atoms of metal. \ . . Hg 4 



C 4 H 2 8 Hg 4 



Formiate of silver is also a salt of sparing solubility. It is obtained by the 
double decomposition of nitrate of silver with an alkaline formiate, in small 
48 



566 FORMYL. 

leaflets of brilliant whiteness; it is decomposed by heat and resolved into the 
metal, formic and carbonic acids. 

Artificial oil of ants, C 5 H 2 2 (Stenhouse). — This name was applied by 
Dcebereiner to the oil which appears in the preparation of formic acid. It 
was obtained by Dr. Stenhouse in larger quantity than it is produced in the 
ordinary process, by distilling together equal weights of oatmeal or sawdust 
and sulphuric acid diluted with its own bulk of water. In the process for 
formic acid the peroxide of manganese cannot be omitted without greatly re- 
ducing the product,' but here it is entirely left out. When oil of ants is puri- 
fied the taste and smell are very pungent and aromatic, resembling oil of Cassia. 
It catches fire very readily and burns with a strong yellow flame. Its density 
is 1.1006 at 80.6°, (27° centig.;) its boiling point 334.4 (168° centig.) It is 
pretty soluble in water and more so in alcohol and ether. Potassium decom- 
poses it with effervescence; but neither the aqueous nor the alcoholic solution 
of potash has any effect upon it.* 



COMPOUNDS OF FORMYL WITH CHLORINE, BROMINE AND IODINE. 

Proto chloride of formyl, C 2 HC1 = FoGl. — One of the substances which 
Regnault obtained by the action of chlorine upon chloride of acetyl, namely 
C 4 H 2 C1 2 , is considered by Liebig as protochloride of formyl, .its atomic 
weight being divided by two. 

Bichloride of formyl, C 2 HC1 2 = FoCl 9 ; one of the substances formed by 
the action of chlorine upon chloride of ethyl, namely C 4 H 2 C1^, is so con- 
sidered by Liebig, its atomic weight being divided by two. 

Per chloride of formyl, chloroform, C 2 HC1 3 = FoCl 3 . This compound is 
formed in various circumstances. It may be prepared by exposing a mixture 
of chloride of methyl (C 2 H 3 C1) and gaseous chlorine to the direct rays of the 
sun; by distilling chloral with barytes-water or milk of lime, but most conve- 
niently by distilling a dilute solution of chloride of lime with acetone, alcohol 
or wood-spirit. For this purpose 1 part of hydrate of lime is suspended in 
24 parts of water, a current of chlorine sent through it till the greater part of 
the lime is dissolved, and a little milk of lime added to make the liquid alka- 
line. When the solution of chloride of lime has become clear by repose, 
^th of its volume of alcohol is added, and after being left to itself for twenty- 
four hours, the liquid is distilled by a gentle heat in a capacious retort. The 
product has an ethereal odour, and contains perchloride of formyl mixed with 
alcohol, on shaking it with water the perchloride separates as a dense liquid, 
and may be obtained perfectly pure by digesting it upon chloride of calcium, 
and distilling it again with concentrated sulphuric acid. (Liebig's Traite.) 

Perchloride of formyl is a colourless oily liquid, of an agreeable ethereal 
odour and sweetish taste; its density is 1.480 at 64.4° (18° centig.;) its boil- 
ing point 141.44° (60.8° cent.) It is inflamed with great difficulty but burns 
in the flame of a candle colouring it green. The alcoholic solution of potash 
destroys it, converting it into formiate of potash (Dumas,) a property which 
the name chloroform refers to: 

FoCl 3 and 4KO=KO,Fo0 3 and 3KC1. 

The density of its vapour is by experiment 4200, by calculation 4116 : its 
combining measure 4 volumes. Chloroform may be distilled from sulphuric 
acid, potassium or potash without being sensibly altered. Exposed with chlo- 
rine to the direct rays of the sun it is decomposed and converted into hydro- 

* Dr. Stenhouse, Phil. Mag., 3rd Series, vol. 18, p. 122. 



CHLOROFORM. 567 

chloric acid and a particular chloride of carbon C 2 C1 4 , which boils at 172.4° 
(78° centig.,) and of which the density of the vapour is 5300, and combining 
measure 4 volumes (Regnault.) This chloride of carbon has been looked 
upon as a formic acid in which both the hydrogen and oxygen are replaced by 
chlorine : 

C 2 C1+C1 3 ; 
while the well known sesquichloride of carbon is related in the same way to 
acetic acid : 

C^Cl. + Cl,. 

When the former chloride of carbon is made to pass in vapour through a 
porcelain tube at a dull red heat, it is divided into two new chlorides of carbon, 
of which the composition is expressed according to M. Regnault, by CC1 and 
CC1 3 . 

Clilorhy drate of chloride of formyl, 2C 2 HC1, HC1 ; one of the products of 
the action of chlorine upon the chlorhydrate of the chloride of acetyl. 

Perbromide of formyl, bromoform, C 2 HBr 3 — FoBr 3 ; prepared like the 
perchloride, and very analogous to it in properties ; its density is 2.10. It is 
less volatile than the perchloride, and more easily decomposed by alkalies. 

Periodide of formyl, iodoform, C 2 HI 3 =FoI 3 . — This is a yellow volatile 
substance discovered by Serullas, which is often described as an iodide of car- 
bon. ' It is obtained on adding an alcoholic solution of potash to a solution of 
iodine in alcohol, till the last is discoloured, carefully avoiding any excess of 
alkali. The alcohol is then expelled by gentle evnporation, and the iodide of 
formyl is deposited in crystals, which are purified from iodide of potassium by 
washing with pure water. This compound is formed in consequence of the 
decomposition of 1 atom of alcohol and 6 atoms of potash, by 8 atoms of 
iodine, by which one atom of periodide of formyl, 1 atom of formiate of pot- 
ash, 5 atoms of iodide of potassium and 4 atoms of water are produced (Liebig.) 



1 atom of alcohol C 



8 atoms of iodine I 3 

6 atoms of potash 6 K ( 



C 4 H^I.K, 



Equivalent to : 



1 atom of periodide of formyl. . . . C 2 H I 3 

1 atom of formiate of potash. . . . C 2 H 4 K 
5 atoms of iodide of potassium . . . I 5 K, 

4 atoms of water H,O t 



C^O.I.K, 

Iodoform crystallizes in brilliant yellow plates, and has a characteristic 
odour suggesting that of saffron. It is insoluble in water, but very soluble in 
alcohol, ether and wood spirit. It sublimes at 212°; at 248° it undergoes de- 
composition and is resolved into carbon, iodine and hydriodic acid. It gives 
a peculiar liquid of a deep red colour and density 1.96, when distilled with 
chloride of phosphorus or with corrosive sublimate ; this liquid contains chlo- 
rine, iodine and formyl. 

Sulphuret of formyl, FoS 3 ? (Bouchardat.) A liquid obtained by distilling 
1 part of iodide of formyl with 3 parts of sulphuret of mercury ; hydrate of 
potash converts it into sulphuret of potassium and formiate of potash. 



568 FORMYL. 

Action of chlorine upon oxide of methyl. — Chlorine gas decomposes the 
oxide of methyl gas, forming hydrochloric acid and the following products, as 
observed by M. Regnault: 

Density. Boiling point. Density of 
vapour. 

Oxide of methyl C 2 H 3 1570=2v. 

Monochlorinated oxide of methyl . C 2 ~? O 



1.315 105° cent. 4047=2 v. 



Bichlorinated oxide of methyl. . C 2 ^ O 1.606 130° « 6367=2 v. 

Perchlorinated oxide of methyl. . C 2 C1 3 2 1.594 212° " 4670=4 v. 

The combining measure of perchlorinated oxide of methyl differs, it will be 
observed, from the other members of the series. (Annales de Chimie, etc. lxxi. 
353.) 

Chlorine is absorbed with great avidity by hydrate of oxide of methyl and a 
heavy oil formed, which has not yet been fully examined. 

Action of chlorine upon chloride of methyl. — This also gives rise to a series 
of compounds, in which the proportion of chlorine increases as the action is 
prolonged. (Regnault.) 

Density. Boiling point. Density of 

vapour. 

Chloride of Methyl C 9 H 3 C1 1738=4 v. 

Monochlorinated ditto. . . . C 2 H 2 C1 2 1.344 30.5° cent. 3012=4 v. 

Bichlorinated do. (chloroform.) C 2 H CI 3 1.491 608° „ 4230=4 v. 

Perchlorinated ditto C 2 C1 Cl 3 1.599 78° „ 5245=4 v. 

The monochlorinated chloride of methyl has an odour which is very sharp 
and is similar to that of Dutch liquid; treated with an alcoholic solution of 
potash, the former liquid gives only a very trifling precipitate of chloride of 
potassium, and distils over almost entirely without change. 

The perchloride of carbon, C 2 C1 4 , which is named above perchlorinated 
chloride of methyl, is not altered by a solution of hydrosulphuret of the sulphuret 
of potassium. It is decomposed by heat and gives different chlorides of carbon 
according to the temperature. 

At a dull red heat, this chloride C 2 C1 4 appears to be converted into another 
chloride of carbon C 2 C1 3 , supposing the combining measure of the latter to be 
4 volumes, its density being 4082. This new chloride of carbon will therefore 
be isomeric with Faraday's sesquichloride C 4 C1 6 , but of only half the density. 
When decomposed at a higher temperature it gives small silky crystals of the 
chloride of carbon of Julin, CC1. Lastly at a bright red heat the liquid chloride 
of carbon C 4 C1 4 is the principal product. 

Chlorine acts readily upon the sulphuret of methyl and upon the compounds 
of oxide of methyl with acids or the compound methylic ethers. A benzoate 
and acetate of an oxichloride of formyl have been produced, having the follow- 
ing formulae, (Malaguti :) 

C 2 H^2-fBzO. 
C 2 H^ l2 -fAcO v 

A mixture of iodine, nitric acid and wood spirit left to itself for a long time, 
deposits yellow crystals. Bromine in the same circumstances gives a heavy 
oily liquid (Aim©.) 



XYLITE. 569 



SECTION III. 



PRODUCTS OF THE DISTILLATION OF WOOD HAVING SOME RELATION 
TO OXIDE OF METHYL. 

Xylite, lignone (Gmelin,) a liquid which exists in commercial pyroxylie 
spirit, and is separated from the hydrate of oxide of methyl by distillation from 
chloride of calcium at 212°. MM. Weidmann and Schweizer, in their last 
memoir on these products, assign to xylite the formula C 6 H 6 2 i. The density 
of its vapour was by experiment 2177, by theory 2159 ; its boiling point 142.7° 
(61.5° centig. ;) density 0.816. Pure xylite has an agreeable, sharp odour, and 
empyreumatic taste. It is miscible with water, dissolves but little chloride of 
calcium, and burns with a white flame. 

Mesiien, C 6 H 6 3 (Weidmann and Schweizer,) a liquid obtained by distilling 
equal parts of sulphuric acid and xylite, in which chloride of calcium is wholly 
insoluble. Its density is 0.808 ; boiling point 145.4° (63° centig.) 

Xylitic acid, G^E^C^i (W. and S.,) obtained by treating anhydrous xylite 
with hydrate of potash. The salt thus formed is supposed to be a compound 
of xylitate of potash with xylite, 3(KO,C ^O^HC^O,,*. It is readily 
soluble in wood spirit, but is insoluble in anhydrous xylite. Xylite oil and 
xylite resin are two other substances contained in an oil, formed, among other 
products, by the action of an excess of hydrate of potash upon xylite. 

Mesite, C 6 H 6 2 (W. and S.) This liquid which, in its physical properties, 
very much resembles mesiten, exists in crude proxylic spirit, and comes over 
late in its rectification. Mesite may, therefore, be separated, by distillation with 
water, from xylite, as the latter passes over early. Mesite is also formed by 
the action of potash and potassium upon xylite. It is colourless, volatile, and 
of an ethereal odour, boils somewhat above 158°, and is soluble in water. 

Xylite naphtha, C 6 H 6 0,i. — By the action of hydrate of potash upon mesite, 
acetic acid is formed and xylite naphtha. When pure, this liquid is colourless 
and very fluid, having an odour resembling oil of peppermint, but slightly solu- 
ble in water, soluble easily in alcohol, wood-spirit, xylite and ether. It boils at 
230°, and burns with a white and smoky flame. 

The principal products of the treatment of xylite-naphtha by an excess of hy- 
drate of potash or potassium are xylite-oil and xylite-resin. 

Xylite-resin, C 24 H 18 3 ; when pure, is a reddish, brown, brittle mass, fusi- 
ble under 212°, but decomposed by a higher temperature. It is insoluble in 
water, or in solution of potash, and gives no precipitate with an alcoholic solu- 
tion of acetate of lead. It is readily dissolved by alcohol, wood-spirit, xylite and 
ether. 

Xylite-oil, C 12 H 9 0. To obtain this oil pure, it is necessary to act upon 
xylite with a great excess of hydrate of potash. It is colourless, but usually 
yellow, lighter than water and nearly insoluble in it, readily dissolved by alco- 
hol, etc. It has a bitter, burning taste, a peculiar odour, boils considerably 
above 392° (200° centig.) and may be distilled without decomposition. It burns 
with a white, very smoky flame. When decomposed by hydrate of potash, 
xylite-oil gives acetic acid and a peculiar resin, C 48 H 36 3 ; not so fusible as. 
xylite-resin. 

When 1 part of anhydrous acetone is gradually mixed with 2 parts of hydrate 

48* 



570 COMPOUNDS CONTAINED IN WOOD TAR. 

of potash, well pulverized, the vessel being kept cool, and the mass mixed after 
six or eight days with water, a brown oily liquid separates ; this may be washed 
with water to free it from undecomposed acetone, and distilled with water to 
separate it from a resinous body. This oil has the same boiling point and com- 
position as xylite-oil, and appears to be identical with it. The resin has also the 
same composition as xylite-resin.* 

Methol, C 12 H 9 ; a liquid produced by the distillation of xylite with sulphuric 
acid ; pure wood-spirit does not yield it, although it was first obtained by the 
treatment of the crude spirit ; it is a hydrocarbon, and contains no oxygen. It 
does not mix with sulphuric acid, but by long digestion and agitation, it disap- 
pears entirely, and is partly converted into a black resin, C 24 H 16 0, which is 
insoluble in alcohol and wood-spirit, but soluble in ether and xylite. Methol is 
not converted into this resin by the action of air. The acid solution neutralized 
with carbonate of lime gives a white crystalline salt, containing methol-sulphu- 
ric acid, of which the formula when free is HO,S0 3 -f Cj 2 H 9 ,S0 3 , or perhaps 
rather HO,C 12 H 3 S 2 ? -f HO.f 

Mr. Scanlan has shown that crude wood-spirit contains free aldehyde, which 
he has extracted from it in a state of purity by submitting the crude spirit to 
successive distillations. L. Gmelin obtained acetone from the wood-spirit of the 
French manufactories ; it distilled over first when the crude spirit was rectified 
from chloride of calcium. 

Pyroxanthin, eblanin,\ C 21 H 9 4 (Gregory and Apjohn;) a crystalline sub- 
stance of an orange colour, obtained by Mr. Scanlan on distilling crude pyrox- 
ylic spirit from slaked lime. It remains with the lime, and after neutralizing 
the latter with acetic acid, may be taken up by alcohol, from which it is de- 
posited in long needles or prisms having the colour of carbazotate of potash. It 
is insoluble in water and in alkalies, but soluble in alcohol, ether and concentrated 
acetic acid. It sublimes at 273°, but does not melt till it is raised to the tem- 
perature of 291°. Concentrated sulphuric acid dissolves it, and assumes a red 
blue colour. § 



SECTION IV. 



OTHER PRODUCTS OF THE DISTILLATION OF WOOD, CONTAINED 

IN TAR. 

Paraffin is a particular hydrocarbon, produced in the distillation of wood, 
and in many other circumstances, which has the same composition per cent, as 
olefiant gas, or CH. It is a crystalline substance, transparent and colourless, 
soft and not unlike stearic acid, inodorous and tasteless, fusible at 110.6° 
(43.75° centig.,)and capable of being distilled at a higher temperature without 
alteration. A cotton-wick which has imbibed melted paraffin, burns without 
smoke or odour, like a wax taper. Its density is 0.870. 

In a chemical point of view, paraffin is distinguished for a remarkable indif- 
ference to other bodies ; hence the name paraffin (parum affinis) assigned to it 



* Lcewig and Weidmann; PoggendorfTs Annalen, 1, 299. 

t F. Weidmann and E. Schweizer; PoggendorfPs Annalen, xiiii, 593 ; xlix, 135 and 293, 
I, 265. 

t From Eblana, Dublin. 

§ Liebig's Annalen for 1837; or Dr. Thomson's organic Chemistry, Vegetables, 
p. 750. 



EUPION, CREOSOTE. 571 

by M. Reichenback, its discoverer. It is not decomposed by chlorine, by alka- 
lies or acids. Paraffin is very soluble in ether and oil of turpentine ; boiling 
alcohol dissolves only 3.45 per cent, of its weight. This and the other princi- 
ples existing in tar are obtained by long and intricate processes, which cannot 
be shortly described.* 

Eupion, C 5 H 6 , is best obtained from animal tar. It is a colourless, very 
limpid liquid (whence its name,) without odour or taste, of density 0.655, not 
frozen by — 4°, boiling at 336.2° (169° centig.,) and distilling over without 
change. It burns easily by means of a wick, with a bright flame and no smoke. 
Eupion in insoluble in water, but soluble in alcohol. It is not altered by potas- 
sium, by chlorine or iodine, which it dissolves, nor by acids or alkalies. — 
(Reichenbach, Ann. de Chim. 1, 69.) 

Creosote, C 7 H^iO (Ettling,) is present in wood-smoke, in tar, and generally 
in wood-vinegar (pyroligneous acid,) to which it communicates its odour, taste 
and antiseptic properties. It is an oily colourless liquid, of high refracting power, 
of which the odour is penetrating and disagreeable, analogous to that of smoked 
meat, and the taste burning and very caustic. Its density is 1.037 at 68° ; it 
boils at 397.4° (203° centig.,) and is not frozen by a cold of —16.6° (—27° 
centig.) It burns with a very smoky flame. 

Creosote forms two different compounds with water at the ordinary tempera- 
ture ; one is a solution of 1.25 parts of creosote in 100 parts of water ; the other, 
on the contrary, a solution 10 parts of water in 100 of creosote. Acetic acid 
appears to be a special solvent of creosote ; these two liquids mix in all propor- 
tions. Potassium is decomposed in it with effervescence and formation of pot- 
ash. Creosote forms in the cold two compounds with potash ; one is anhy- 
drous, liquid of an oily consistence, the other hydrated and crystallized in white 
pearly plates; they are both decomposed by all acids, even carbonic acid. It 
mixes in all proportions with alcohol, ether, sulphuret of carbon, oil of petroleum 
and acetic ether. Creosote is remarkable for dissolving a large number of or- 
ganic colouring matters, including cochineal, dragon's blood, litmus, madder, 
saffron, and even indigo, when heated. It coagulates albumen, a property upon 
which its corrosive action upon animal tissues may depend. Butcher-meat or 
fish dipped in it.'and then exposed to air, does not putrefy,! but acquires the agree- 
able flavour of the same kind of food when well smoked. 

Picamar (in pice amarum) is a transparent and nearly colourless liquid, of 
the consistence of an oil somewhat thickened ; its odour is weak and peculiar, 
its taste insupportably bitter and burning, then cooling like that of peppermint. 
Its density is 1.10 at 68° ; its boiling point 518°. It is the bitter principle, ac- 
cording to M. Reichenbach, of all empyreumatic products. It forms crystalline 
compounds with the alkalies and alkaline earths, in which the latter are not neu- 
tralized. It is insoluble in water, but soluble in alcohol and ether. 

Pittac.al, a beautiful colouring matter, discovered by Reichenbach in the oil 
of tar ; the latter substance, when free from acid, assuming a beautiful blue on 
the addition of barytes- water to it. This substance when precipitated or obtained 
by evaporation forms a deep blue mass, solid and friable, like indigo. It assumes 
also a coppery lustre, like indigo, when rubbed. It is inodorous, insipid and not 
volatile. Pittacal is insoluble in water, but is suspended in that liquid in a state of 
such minute division as to pass through a paper filter, and colour the liquid blue. 
Its solution in acetic acid is of a rose red colour, and recovers a very fine blue 
colour on the addition of an excess of alkali. M. Reichenbach recommends it 

* Reichenbach ; Ann. de Chimie, etc. t. 30, p 69. Also Dr. Thomson's Organic Chemis- 
try, Vegetables, p. 723 ; or Traile de Chimie, par M. Dumas, t. v. p. 652. 
t Hence the name creosote, from jc/js*? flesh, and o-og® I save. 



572 PRODUCTS OF THE DISTILLATION OF COAL. 

as a re-agent even more sensible than litmus to the action of acids and alkalies. 
It is not soluble in alcohol, ether or eupion. It is not altered by air and light. 

Pittacal gives precipitates of a fine violet blue colour, with acetate of lead, 
chloride of tin, ammoniacal sulphate of copper and acetate of alumina. This 
substance may be available ultimately in the opinion of M. Reichenbach, as a 
colouring matter in dyeing. 

Besides the bodies described, other substances have been found among the 
products of the distillation of wood, to which the names cedriret, chrysene, 
pyrene and capnomor have been given. 



PRODUCTS OF THE DISTILLATION OF COAL, 

The general products of the distillation of coal, which appear in gas-making, 
are: 1, the residuary carbon or coke; 2, gaseous compounds of carbon and 
hydrogen, including olefiant gas (page 301;) 3, a watery liquid, containing 
salts of ammonia; and, 4, tar. 

When the tar is distilled with water, an oily liquid comes over, and there 
remains behind a black resinous substance, or pitch, of the nature of which 
little is known. The oil is a mixture of several bodies, some of which are 
capable of combining with bases, and some with acids. Particular substances 
have been isolated, to which the names, leucol, pyrrol, cyanol, carbolic acid, 
rosolic and brunoHc acids are applied, but the most remarkable product in 
coal-tar is naphtaline, which is sometimes found sublimed pure, in white 
crystalline plates, in the gas apparatus. 



NAPHTALINE. 

Formula: C 20 H 8 . M. Laurent has observed that this substance is best ob- 
tained from tar which is somewhat old. The tar is boiled in air till it is de- 
prived of water, and then distilled in a retort with a copper adopter or con- 
necting tube, and glass receiver. The first portion of oil distilled is of a 
yellowish colour, which becomes dark coloured in air, and allows much 
naphtaline to fall when cooled to 14° or 10° Fahr. If re-distilled, and the 
last portions received apart, they yield naphtaline in large quantity when 
cooled. To purify naphtaline, it is crystallized twice from alcohol, taking 
care to press the crystals each time in folds of cotton cloth. If the oil is sub- 
mitted for sometime to a current of chlorine, it yields afterwards an increased 
product of naphtaline. 

Naphtaline is in transparent and colourless plates, has a strong peculiar and 
not unpleasant odour, a burning aromatic taste, is denser than water, insolu- 
ble in it, melts at 176°, boils at 422.6° (217° centig.) and condenses in shining 
leaflets. The density of its vapour is 4528 by experiment, and 4488 by 
calculation; its combining measure is 4 volumes. Naphtaline burns, when 
heated, with a white smoky flame. It is very soluble in alcohol and ether, 
and crystallizes from these solutions on dilution with water. Naphtaline is 
peculiarly the product of a high temperature, and is furnished by alcohol and 
organic matters in general when heated to redness. 

Naphtaline dissolves in concentrated sulphuric acid, upon the application of 
heat; with anhydrous sulphuric acid it combines when heated, and forms a 
fine purple red liquid. The compound contains three peculiar acids, which 
on diluting the mass with water and neutralizing it with carbonate of barytes, 
are obtained in three different barytes salts, which may be separated and dis- 



CHLORIDES OF NAPHTALINE. 573 

tinguished from each other by their unequal solubility and different crystal- 
lization. They are: 

Nap htalin- hypo sulphuric acid or sulphonaphtalic acid, HO-f-C 2o H 8 S„0 5 . 
It is soluble in water and crystallizes, is sour and bitter, with a metallic after- 
taste. The hyposulphuric acid it contains is not neutralized by the naphta- 
line, and combines with the usual proportion of base to form a neutral salt. 
sulphonaphtalate of barytes BaO + C 20 H 8 ,S 2 O^, crystallizes in brilliant 
light spangles, burns in the flame of a candle, is insoluble in alcohol. It parts 
with an atom of water when heated; its formula may then be BaO + C 20 H., 

JS aphtin-hypo sulphuric acid or sulphonaphtic acid, H0+C 11 H 4 i0,S 2 
O s , is not crystallizable, and very soluble in water. 

Glutinhypo sulphuric acid is separated from its salts by hydrochloric acid 
as a milky substance, which falls and collects together in transparent, clammy 
drops; its salts do not crystallize. 

When naphtaline is dissolved in excess by sulphuric acid, and water added, 
the excess is precipitated, but in an altered state, for when the precipitated 
naphtaline is distilled with water, it leaves behind a fatty matter, from which 
alcohol separates two new compounds, sulphonapht aline, C 20 H S , S0 2 and 
sulphonaphtalide, C 24 H 10 ,SO 2 . Both are inodorous and insoluble in water. 

By the action of chlorine upon naphtaline, two compounds of that substance 
with chlorine in different proportions are formed; and by the abstraction of 
hydrochloric acid from these, or continued action of chlorine, several other 
compounds are produced: 

1. C 20 H 8 C1 2 ==C 20 H 7 C1 -fH CI 

2. C 20 H 8 C1,=C 20 H 6 C1 2 + H 2 C1 2 

3. C 20 H 6 C1 2 = C 20 H 6 C1 2 

4. C 20 H 6 C1 6 =C 20 H 4 C1 4+ H 2 C1 2 

5. C 20 H 5 C1 3 =C 20 H 5 C1 3 

1 

The first of these compounds chlorhydrate of chloronaphtalase of Laurent 
is formed when naphtaline absorbs chlorine gas at the usual temperature; it is 
a yellow oil, denser than water and insoluble in it. When treated with pot- 
ash it loses HC1, and gives the chloronaphtalase of Laurent, C 20 H 7 C1. 

The second, chlorhydrate of chloronaphtalcse of Laurent, when naphtaline 
is saturated with chlorine gas at 140°. It crystallizes from ether in transpa- 
rent rhomboidal tables, requires a temperature of 320° to fuse it, and forms a 
crystalline mass on cooling. 

The third, chloronaphtalese of Laurent, is produced by the distillation of 
the second, or by treating it with an alcoholic solution of potash, with the 
separation of 2 atoms of hydrochloric acid. It crystallizes from alcohol in 
rhombic prisms, is tasteless and inodorous, and fuses at 111.2° (44° centig.) 
Two other isomeric compounds of the same formula exist, one an oil, the 
other obtained by potash. 

The fourth compound, chlorhydrate of chloronaphtalase of Laurent, is pro- 
duced by the action of chlorine gas upon the third, at the usual temperature. 
It much resembles the body from which it is derived, fuses at 105.8° (41° 
centig.,) and may be sublimed without change. 

The fifth compound, chloronaphtalise of Laurent, is the product of the 
action of chlorine on the first or fluid chloride of naphtaline in sunshine, or 
with heat and subsequent distillation of the oil formed. It crystallizes from 
ether in large striated prisms, which are colourless, inodorous, soft, like bees'- 
wax, fusible at 163°. 4 (73° centig.) This compound is a naphtaline in which 



574 PRODUCTS OF THE DISTILLATION OF COAL. 

3 atoms of hydrogen are replaced by 3 atoms of chlorine. (Laurent, Ann. de 
Chim. &c. lxvi, 196.) 

M. Laurent has obtained two neutral substances and two acids, from the 
action of nitric acid upon the naphtalic chlorides (Ann. de Chim. Ixxiv, 26:) 

Oxichloronaphtalose - C 20 H 4 Cl 2 O 2 -f HO 

Chloronaphtalosic acid - C 20 H 4 C1 3 -f-0 2 

Naphtalosic acid - - <|(Cj & H 4 4 -f-0 2 ) 

Oxichloronaphtalenose - C 18 H 4 C1 3 

Nitronaphtalide (nitronaphtalase,) C 20 H--fNO, t , is produced on heating 
naphtaline with nitric acid, by the separation of HO. It crystallizes from 
alcohol in four-sided prisms, of a sulphur-yellow colour, fuses at 109°.4 (43° 
centig.,) and may be sublimed when cautiously heated; when suddenly heated 
it burns. 

Nitronaphdehyde (nitronaphtalese,) C 2o H 6 -f2N0 4 , is formed by boiling 
the former compound, or naphtaline and nitric acid till no oily body floats on 
the surface of the liquid. It falls upon the cooling of the liquid as a yellow 
crystalline powder, fusible at 365°, which may be sublimed without change, 
and is insoluble in water and alcohol. (Laurent.) 

The action of nitric acid on naphtaline being continued for a longer time 
and at a high temperature, after the expulsion of the nitric acid in nitrous 
fumes and the sublimation of the naphtalese, a feeble explosion takes place, 
and a coaly mass remains in the retort. By repeating the treatment of this 
mass with nitric acid, M. C. de Marignac obtained the following three new 
products: 1, Nitronaphtalise, C 2p H 10 N 3 12 or C 20 H l0 -f3NO 4 ; a yellow, 
glutinous, resinous substance, insoluble in water, dissolved out of the mass by 
ether. This substance is named by Marignac according to the plan followed 
by Laurent of distinguishing compounds obtained successively from the same 
root by the vowels, a, e, i, o, etc.; the two preceding compounds being nitro- 
naphtalase and nitronaphtalese, this falls to be named nitronaphtalise. Alka- 
lies decompose this substance, and convert it into — 2, a brown matter, C 12 H 3 
N0 5 , carbonic acid and ammonia; S,nitronaphtalic acid, 2HO-f C 16 H 5 N0 12 ; 
a bibasic acid, soluble in water, forming crystallizable salts. The salt of am- 
monia is white, with the lustre of mother of pearl, and resembles the crystal- 
line plates of naphtaline; it is readily dissolved by water, and pretty soluble 
in alcohol. The salts of silver and barytes contain two atoms of metallic 
oxide, the salt of lead four atoms. 

M. de Marignac also obtained a volatile liquid, which distilled over with the 
excess of nitric acid, in treating the hydrochlorate of chloronaphtalese (C 20 H 8 
Cl 4 ) with that acid, of which the constitution is remarkably simple, CC1N0, 4 or 
CCl-{-N0 4 . This liquid, which is not named, is perfectly colourless, transpa- 
rent, of density 1.685 at 59°, of an odour excessively irritating, like that of 
chloride of cyanogen, and affecting the eyes, neutral to test-paper. Water dis- 
solves a mere trace of it, but acquires thereby its smell and taste. It dissolves 
easily in alcohol and ether ; nitric and hydrochloric acids dissolve only a very 
little of it. Its boiling point appears to be not greatly above 212°. The 
aqueous solution of potash has no action upon it, the alcoholic solution dissolves 
it easily, and after a time, a crystalline potash-salt falls, which is decomposed 
when heated, with explosion. The density of its vapour was not ascer- 
tained. 

The naphtalic acid, which is formed and remains in the retort in the pre- 
ceding process, did not possess the properties or composition of the acid which 
M. Laurent obtained by a similar process. Marignac's naphtalic acid contains 



BITUMEN. 575 

nitrogen, with carbon and hydrogen in the proportion of C 8 H 5 , which is incon- 
sistent with the formula of the following acid * 

Nuphlalic acid, HO-fC 8 H 2 3 , is formed on heating with nitric acid the 
second compound or solid chloride of naphtaline in the foregoing list (the chlo- 
rhydrate of chloronaphtalese; ruddy fumes are given off, and the acid solution 
gives on concentration a white crystalline crust, which is naphtalic acid. One 
equivalent of chlorhydrate of chloronaphtalese and 10 equivalents of oxygen 
give 2 equivalents of naphtalic acid, 2 equivalents of oxalic acid, and 4 of hy- 
drochloric acid : 

C 20 H 3 C1 4 and 10O=2C 8 H 2 O 3 and 2C 2 3 and 4HC1. 

It crystallizes by sublimation in long thin prisms, resembling benzoic acid, 
which are inodorous, have a weak taste, fuse at 221°, are soluble with difficulty 
in water, have an acid re-action and form salts with bases. (Laurent.) 

Paranap lit aline, C 30 H 12 ; accompanies naphtaline in tar, and is deposited 
by the distilled oil when greatly cooled in crystalline grains. It is distinguished 
from naphtaline by its sparing solubility in boiling alcohol. It is also less fusi- 
ble and less volatile, fusing at 356° and boiling above 572° (300° centig.) 
Its best solvent is oil of turpentine. It contains carbon and hydrogen in the 
same proportion as naphtaline, but on taking the density of its vapour, it is found 
that 3 volumes of naphtaline represent only 2 of paranaphtaline ; the density of 
the latter is 6732. (Dumas and Laurent, Ann. de Chim. 1, 187.) 



SECTION V. 



BITUMEN. 

A tarry matter known as bitumen, is found native in various parts of the 
world, sometimes so consistent as to be termed pitch or asphalt, and often liquid 
and thin, as the native petroleum or naphtha of Persia and Rangoon. The lat- 
ter, however, always holds much fixed matter in solution. 

According to the recent observations of MM. Pelletier and Walter, natural 
naphtha consists of several liquid and one solid compound, paraffin namely, 
which it contains ready formed. The liquid compounds are hydrocarbons, 
which these chemists name naphtha, naphtene and naphtol. They are separated 
from each other by distillation, as they have different boiling points. 

Naphtha, C 1X H 13 ; boils between 185° and 194°, is decomposed by sulphu- 
ric and nitric acid, particularly with the aid of heat, less affected by chlorine ; 
iodine dissolves in it. The density of its vapour is by observation 3400, by 
calculation 3390. 

Naphtene, C 16 H 16 ; is denser than naphtha, oily, and boils at 239°. The 
density of its vapour is by observation 4000, by calculation 3920. Naphtene 
thus forms, from its composition, the fourth member of the series of hydrocar- 
bons to which olefiant gas belongs : 

Methylene (hypothetical) C 2 H 2 # 
Olefiant gas . . . C 4 H 4 
Oil gas .... C 8 H 8 
Naphtene . . . C l6 H 16 
Cetene . . . . C 32 H 3 » 

* C. de Marignac, in Liebig's Annalen, vol. 38, pp. 1 & 13. 



576 AMYGDALIN. 

Naphtol, C 24 H 22 ; like naphtene, greatly resembles naphtha in its chemical 
properties, boils at 374°. The density of its vapour is by observation 5300, by 
calculation 5600. Naphtol and naphtene give compounds with chlorine, bro- 
mine and iodine. 

It is evident from its composition that natural naphtha must be the product of 
the action upon vegetable matter of a high temperature, which has not however 
exceeded a red heat.* 



CHAPTER IV. 

AMYGDALIN AND THE BODIES DERIVED FROM ITS DECOMPOSITION. 

SECTION L 

AMYGDALIN. 

The formula of anhydrous amygdalin is C 40 H 27 NO 22 . 

This is a principle in the bitter almond and berries of the cherry-laurel, of 
which the discovery is due to Robiquet and Boutron-Charlard. Its singular 
decomposition and the nature and relations of the products resulting from it 
were ably investigated by MM. Liebig and Wcehler in a memoir, the publication 
of which formed an important era in the progress of organic chemistry (An. de 
Chim. li, 273.) 

A fat oil is obtained by submitting blanched bitter almonds to great pressure 
between two hot iron plates ; the matter which remains, or the almond cake, is 
the source of amygdalin. It is treated with boiling alcohol of 93 or 94 per cent, 
applied to it in successive portions, and the alcoholic solutions evaporated by a 
water-bath to a syrupy consistence. To remove a quantity of sugar which 
prevents the amygdalin from crystallizing, the residue is diluted with water, a 
little yeast added to it, and it is left to ferment in a warm place. After the 
fermentation ceases, the liquid is filtered and evaporated again by a water-bath 
to a syrupy consistence. On mixing the syrup with a portion of strong alcohol 
of 94 per cent., all the amygdalin precipitates in the form of a white crystalline 
powder, which is pressed in folds of filter paper, and afterwards purified by new 
crystallizations from alcohol. (Liebig.) 

As crystallized from alcohol, amygdalin retains a portion of that substance in 
combination, which it loses when exposed to air. At the ordinary temperature 
it is scarcely soluble in anhydrous alcohol, but is more easily dissolved by boiling 
alcohol. It is very soluble in water, and crystallizes from a solution saturated 
at 104° in large transparent prisms, of a silky lustre which contain 10.57 per 
cent, of water, or 6 atoms ; dried in vacuo over sulphuric acid the crystals lose 
3.52 per cent, of water equivalent to 2 atoms. The crystals are not volatile, 
but are decomposed by a high temperature, diffusing the odour of hawthorn, 
and leaving a bulky charcoal. 

* Journal de Pharmacie, t. 26, p. 549. 



BENZOIC ACID. 577 

Dry chlorine has no effect upon amygdalin ; humid chlorine converts it into 
a bulky white powder, insoluble in water and alcohol, which has not been 
examined. Heated with dilute nitric acid, or with peroxide of manganese and 
dilute sulphuric acid, amygdalin produces ammonia, volatile oil of bitter almonds, 
benzoic acid, formic and carbonic acids. Hypermanganate of potash in decom- 
posing amygdalin gives rise to cyanate and benzoate of potash. Caustic alka- 
lies convert amygdalin into ammonia, which is disengaged, and amygdalic acid, 
a peculiar acid, which remains in combination with the alkali. 



AMYGDALIC ACID. 

Formula: HO-fC 40 H 26 O 24 . This acid was first obtained by Liebig and 
Woehler, by the action of alkalies upon amygdalin. It is best prepared by dis- 
solving amygdalin in barytes-water, and maintaining the mixture in a state of 
ebullition, so long as ammonia is disengaged ; the barytes is then removed by 
sulphuric acid, and the liquid evaporated by a water bath. In the formation 
of this acid, 1 atom of amygdalin and 2 atoms of water are resolved into 1 atom 
of ammonia and 1 atom of anhydrous amygdalic acid: 

C 40 H 27 NO 22 and 2HO = C 40 H 26 O 24 and NH 3 . 

Amygdalic acid is obtained by evaporation as a transparent colourless amor- 
phous mass; it has a very agreeable acid taste, is insoluble in alcohol and ether, 
but so soluble in water as to deliquesce in damp air. 

Nitric acid and the mixture of peroxide of manganese and dilute sulphuric 
acid act on amygdalic acid as on amygdalin, allowing for the absence of ni* 
trogen from the former, the products being volatile oil of bitter almonds, formic 
and carbonic acids, all of which are disengaged in the state of gas. 

Little is known of the amygdalites; they appear to be in general soluble 
salts, with the exception of a basic salt of lead. Amygdalin, it will be ob- 
served, has the composition of amvgdnlate of oxide of ammonium, from 
which the elements of 3 atoms of water have been abstracted; or it has lost 1 
atom of water more than a true amygdalamidc (Liebig.) 



SECTION II. 



BENZOYL SERIES OF COMPOUNDS. 

Benzoyl or benzo'ile,* C l4 Hj.0 2 = Bz. This is the hypothetical radical 
of a series of compounds, including benzoic acid, (from which it derives its 
name,) and the essence or volatile oil of bitter almonds. The last substance 
is derived from amygdalin by various means. Amygdalin exists also in the 
kernels of many fruits, and in the leaves of the laurel. 



BENZOIC ACID. 

Formula: HO,C 14 H ? 3 = HO,BzO. This acid exists ready formed in 
several resins, particularly benzoin and dragon's blood. It is produced by the 
decomposition of amygdalin by oxidating matters, by the oxidation of essence 
of bitter almonds, of hippuric acid, and in many other circumstances. 

* Benzule of several English chemical writers. 
49 



578 BENZOYL. 

To prepare benzoic acid from the resin, Dr. Mohr directs 1 pound of it to 
be broken and spread uniformly in a cast iron basin, 8 or 9 inches in diameter 
and 2 inches deep, the mouth of which is then covered, like a drum, by un- 
sized paper pasted down at the edges. A cylindrical vessel of paper of the 
size and ordinary form of a maivs hat is pulled over this, and bound about the 
basin by a thread. The basin is then placed on a sand-bath for three or four 
hours, attention being paid to the management of the heat, for the beauty and 
purity of the product depend entirely upon the slowness and regularity with 
which the sublimation is effected. The paper cylinder is found completely 
filled with superb crystals of benzoic acid of splendid whiteness and perfectly 
free from the black empyreumatic oil which they are generally soiled with; 
but having on the contrary a strong and very agreeable odour of benzoin. 
This process yields about 4 per cent, of benzoic acid. 

Benzoic acid is also prepared in the humid way; the resin is finely pulve- 
rized and care taken to mix it intimately with an equal weight of hydrate 
of lime; the mixture is then boiled with twenty times its weight of water by 
which the benzoate of lime is dissolved; the solution is filtered, and after being 
concentrated to about one-fifth of its bulk, hydrochloric acid is added, by which 
the benzoic acid is liberated, and crystallizes on cooling. The chief point to 
be attended to in this process is the mixing of the resin and hydrate of lime, 
which must be intimate, otherwise the mass agglomerates in boiling water and 
the benzoic acid can only be obtained by reducing the mass to powder and 
mixing it again with hydrate of lime. 

The benzoic acid may be purified by a second sublimation, or by sending 
a stream of chlorine through its solution in boiling water (Liebig's Traite.) 

Benzoic acid crystallizes when sublimed in long hexagonal silky needles; 
when pure it is colourless and inodorous; but it acquires by heat an odour, ana- 
logous to that of benzoin. Its taste is sweet and hot, but quite peculiar. It 
reddens litmus feebly; water dissolves T l 7 of its weight of benzoic acid at 212°, 
and -gfc only at the ordinary temperature. It is soluble in two parts of alcohol 
and the same quantity of ether, and dissolves also in oil of turpentine. Ben- 
zoic acid fuses at 248°, and sublimes at 293°, phosphorescing in the dark; it 
boils at 462°. 2 (239° centig.;) the density of its vapour is 4270 by experiment, 
and 4260 by calculation. Heated in open air it allows a white vapour to dif- 
fuse, which greatly irritates the fauces and provokes coughing. It is very 
inflammable, and burns with a white smoky flame without leaving any resi- 
due. 

Benzoates. Benzoic acid is readily dissolved%y alkalies and alkaline car- 
bonates, and also by phosphate of soda. Several insoluble benzoates are dis- 
solved, according to Lecanu and Serbat, by acetates of potash and soda and 
nitrate of soda, while they are insoluble, in nitrae and sulphate of potash, and 
sulphate of soda. Ammonia forms a neutral and acid benzoate; the last pre- 
sents itself in large regular crystals. The salts of potash, soda, lithia, and 
magnesia are very soluble, and crystallize with difficulty. The salt of lime 
is soluble in 20 parts of cold water, and in a greater proportion in boiling 
water; it crystallizes in flexible needles, or brilliant prisms, which contain 1 
atom of water of crystallization. Benzoate of alumina is obtained as a crys- 
talline precipitate. Benzoates of manganese and ■protoxide of iron are pretty 
soluble. Neutral benzoate of peroxide of iron, Fe. 2 3 -j-3BzO, is soluble in 
water and alcohol and crystallizable. But peroxide of iron is thrown down in 
the form of an insoluble sub-benzoate, of a reddish-white or buff colour, when a 
soluble benzoate is added to a solution of peroxide of iron, previously neutral- 
ized without precipitating any peroxide of iron by means of ammonia. To 
prevent the decomposition of this precipitate and the formation of a soluble 
benzoate of iron, it should be washed by a solution of sal-ammoniac. Ben- 



HYDRURET OF BENZOYL. 579 

zoate of ammonia i3 often employed to separate peroxide of iron from oxides 
of manganese, nickel, and zinc, but when the solution contains at the same 
time alumina, yttria, zirconia, or glueina, the process does not answer, as the 
benzoates of these oxides are equally insoluble with that of peroxide of iron. 
Benzoate of lead is nearly insoluble in water, but soluble in acetic acid, from 
which it maybe obtained crystallized in plates, which contain 2 atoms of 
water, one of which it abandons when dried at 212°. Solutions of an alkaline 
benzoate and trisacetate of lead, give a white anhydrous and insoluble precipi- 
tate, which is basic benzoate of lead consisting of 2 atoms of benzoic acid 
united with 3 atoms of oxide of lead. Benzoate of silver is obtained in colour- 
less needles, flattened and brilliant, on treating a boiling and dilute solution of 
an alkaline benzoate with nitrate of silver, and allowing the liquid to cool. 



HYDRURET OF BENZOYL, OR ESSENCE (VOLATILE OIL) OF BITTER 

ALMONDS. 

Formula C 14 H.0 2 -f H=Bz,H. The crude oil obtained by distilling laurel 
leaves or bitter almonds with water, contains hydrocyanic acid, benzoic acid 
and some benzoine (a solid oil;) it is purified by a new distillation with water, 
protochloride of iron and hydrate of lime in a thin liquid. The oil which 
distils over may be dried perfectly by digestion with chloride of calcium. 

Pure hydruret of benzoyl is a transparent colourless liquid, of high refract- 
ing power; its odour is strong and peculiar having some resemblance to that 
of hydrocyanic acid, its taste burning. It is poisonous. The density of the 
oil is 1.043, its boiling point 356°; its vapour may be transmitted through a 
tube heated to redness without being decomposed. It mllames easily in air, 
and burns with a white smoky flame. It is soluble in 30 parts of water, and 
may be mingled in all proportions with alcohol and ether. Nitric acid dis- 
solves hydruret of benzoyl, but converts it with difficulty into benzoic acid. 
Hydruret of benzoyl is gradually converted in air into benzoic acid by absorb- 
ing 2 atoms of oxygen, an atom of water being formed at the same time which 
combines with the benzoic acid formed. I In presence of an alkali it absorbs 
oxygen rapidly and is transformed almost immediately into a benzoate. 
When mixed with dry hydrate of potash, and distilled at a high temperature 
out of contact with air, it forms benzoate of potash, by the decomposition of 
water, and pure hydrogen gas is disengaged t Submitted to a moderate heat 
with an alkali it gradually produces, according to Fremy, an alkaline benzoate 
and a volatile oily liquid very rich in hydrogen. Dilute solutions of the alka- 
lies, barytes, or lime-water, dissolve hydruret of benzoyl, but do not alter it, 
even when kept for 24 hours at 140° or 160°, provided air is excluded. But 
all these solutions furnish a notable quantity of the solid benzoine, when after 
having added to them some drops of hydrocyanic acid they are exposed to a 
temperature of 158°. On treating hydruret of benzoyl with an alcoholic solu- 
tion of potash, it passes in a few seconds into benzoate of potash which floats 
upon the alcohol; a portion of the hydruret of benzoyl which loses oxygen 
being converted at the same time into an oil of unknown composition retained 
in solution by the alcohol. 

Chloride of benzoyl C 14 H 5 2 + Cl==Bz,Cl; is formed on transmitting 
chlorine gas through dry hydruret of benzoyl, so long as hydrochloric acid is 
disengaged, and heating the yellow liquid to expel the excess of chlorine, till 
it becomes colourless. The atom of hydrogen of the hydruret of benzoyl is 
removed by one atom of chlorine, and replaced by another, as in ordinarv 
substitutions. 

Chloride of benzoyl is a colourless liquid, of a very penetrating and dis- 



580 BENZOYL. 

agreeable odour, which affects the eyes; its density is 1.106; it boils at 383° 
(195° centig.) It may be distilled from lime or barytes without change. It 
mixes with ether and bisulphuret of carbon without decomposition. Cold 
water converts it more slowly than hot water into hydrochloric and benzoic 
acids; with alkalies it produces an alkaline benzoate and chloride of the same 
metal. With alcohol it produces benzoate of ether and hydrochloric acid. 

Bromide and iodide of benzoyl crystallize in transparent colourless plates. 

Sulphuret of benzoyl is obtained by distilling chloride of benzoyl with sul- 
phuret of lead, as a yellow oil, which fixes as a soft crystalline mass, having 
a peculiar disagreeable odour. 

Cyanide of benzoyl is prepared by distilling chloride of benzoyl with cya- 
nide of potassium; it is, after rectification, a colourless oil having a strong cin- 
namon odour which excites tears. 

Benzamide, Bz-J-NH 2 =Bz,Ad; is prepared by saturating chloride of ben- 
zoyl by dry ammoniacal gas; pulverizing the white solid mass which is formed, 
washing it with cold water to remove sal-ammoniac, and dissolving the residue 
in boiling water, which deposites the benzamide on cooling. It crystallizes 
in right rhomboidal prisms, or in small tables of a pearly lustre, fuses at 239° 
into a colourless liquid, and may be distilled at a higher temperature. It is 
soluble in alcohol and ether, as well as in water. Acids and alkalies decom- 
pose it, with the presence of water, into ammonia and benzoic acid. 

Formobenzoi'lic acid, HO-f BzH,C 2 H0 3 . This acid contains hydruret of 
benzoyl in combination with formic acid. It is the result of the action of 
dilute hydrochloric acid upon the crude distilled water of bitter almonds which 
contains the essence and hydrocyanic acid. The latter acid is decomposed in 
contact with water and a strong acid, into ammonia and formic acid, the last 
of which unites in the nascent state with the oil. This acid is a white crys- 
talline powder, very acid, fusible into an oily liquid by heat with loss of water, 
soluble easily in water, alcohol and ether; capable of decomposing with aid of 
heat the acetates, carbonates and benzoates. Its aqueous solution when sub- 
mitted to oxidating agencies, such as chlorine, nitric acid, and peroxide of 
manganese with dilute sulphuric acid, gives carbonic acid and hydruret of 
benzoyl. 

Formobenzoi'lic acid has the same saturating power as formic acid, and be- 
longs to that class of acids into the constitution of which some foreign body 
enters without neutralizing them. In the formation of its salts, the basic 
water of the formula above is replaced by a metallic oxide. 

Benzoate of hydruret of benzoyl; a body which consists of 1 atom of hy- 
dratecl benzoic acid united with 2 atoms of hydruret of benzoyl. It is pre- 
pared by saturating the crude essence of bitter almonds by humid gaseous 
chlorine; after some time the new compound is deposited in a crystalline mass, 
which is washed with cold ether. It forms either a crystalline powder of 
great whiteness, or slender short prisms of a square base, transparent and 
brilliant. It is soluble in alcohol, very slightly soluble in cold ether, and in- 
soluble in water. It is decomposed immediately by an alcoholic solution of 
hydrate of potash, which deposites benzoate of potash after a time in regular 
crystals. 



HIPPURIC ACID. 

Formula: HO-f C, 8 H 8 N0 5 . 

This acid was discovered by Liebig, and obviously belongs to the benzoyl 
series, although its exact place cannot at present be assigned to it with cer- 
tainty, It has been viewed as a compound of benzamide with an organic acid, 



hippuric acid. 581 

namely, C 4 H0 3 (aconitic, fumaric or equisetic acid;) or as a compound of 
hydruret of benzoyl, hydrocyanic and formic acids. It exists in large quan- 
tity in the urine of herbivorous mammifers, and was first derived from that of 
the horse; hence its name. 

To prepare it the fresh urine of the cow or horse is evaporated by a gentle 
heat, care being taken not to allow it to enter into ebullition ; it is then made 
sharply acid by means of hydrochloric acid, and left to itself The hippuric acid 
which crystallizes from this liquid is coloured and impure, but may be purified 
by adding a little hydrochloric acid to it with portions of chloride of lime till the 
odour and colour disappear. 

Hippuric acid crystallizes in pretty large semi-transparent prisms of four sides 
and dihedral summits, which have a slightly bitter taste, and redden litmus 
strongly. They fuse by heat into an oily liquid without loss of weight; at a 
higher temperature the acid undergoes decomposition and is converted into 
benzoic acid and benzoate of ammonia, which distil over in red drops, diffusing 
an agreeable odour like that of the Tonquin bean, which is occasioned by an 
oily product of the reaction; while towards the end of the distillation hydrocyanic- 
acid appears and a porous residue of charcoal. Cold water dissolves -^ of 
hippuric acid, hot water dissolves it very abundantly ; it is more soluble in alcohol, 
and very slightly soluble in ether. 

Hydrochloric acid dissolves hippuric acid without decomposing it; nitric acid 
converts it almost immediately into benzoic acid. Peroxide of manganese and 
sulphuric acid convert it, with the aid of heat, into carbonic acid, ammonia and 
benzoic acid. Boiled with puce coloured oxide of lead, hippuric acid is con- 
verted into benzamide and carbonic acid. 

After the urine of the horse is left to itself for a long time, or evaporated 
rapidly, it contains benzoic acid and no hippuric acid. M. Liebig expresses an 
opinion that hippuric acid is not a product of the animal economy, but comes 
from the food of the animals, in which it may exist ready formed. For it is 
observed that the urine of horses living on green food, always furnishes hippuric 
acid, while the urine of animals fed on dry herbs or hay, which has undergone 
a kind of fermentation, contains only benzoic acid. Mr. Alexander Ure has 
since made the curious observation that benzoic acid taken internally by man 
is discharged in the urine as hippuric acid, while the proportion of uric acid in 
the urine suffers at the same time a great diminution or is reduced to nothing.* 

The hippurates of the alkalies and alkaline earths are soluble and crystalliza- 
ble. Those of the metals proper with the exception of iron are very sparingly 
soluble in cold, but more soluble in hot water and crystallize on cooling. The 
stronger acids separate hippuric acid from all the hippurates; distilled with 
lime or hydrate of potash they give ammonia with an oily liquid supposed to 
be benzin. 



PRODUCTS OF THE DECOMPOSITION OF BENZOYL COMPOUNDS. 

Hyposvlphobenzoic arid 2HO+C 14 H 4 3 ,S 2 5 ; a bibasic acid discovered 
by Mitscherlich. It is prepared by conducting the vapour of anhydrous sul- 



* Proceedings of the Pharmaceutical Meetings at Mr. Bell's, Part 1, vol I. 1841. 

[The views of Mr. Ure have not been confirmed in their full extent by later observers. 
Mr. A. Baring Garrod, (L. and Ed. Phil. Tr. vol. 20, p. 501,) asserts that benzoic acid when 
taken internally is converted into hippuric acid as discharged by the kidneys, but this is 
the only change which takes place; the uric acid undergoing no alteration, the same pro- 
portion existing" in the urine after, as before the administration of the benzoic acid. These 
results are confirmed by the observations of Mr. M. Boye of this city. (Proceedings of 
the centenial anniversary of the Am, Phil. Soc. R. B.] 

49* 



582 BENZOYL. 

• 

phuric acid into a dry receiver containing benzoic acid and surrounded by cold 
water ; a viscid mass is formed like turpentine, which is taken up by water, and 
after the uncombined benzoic acid has subsided from the liquid, the latter is 
neutralized with carbonate of barytes, and after evaporating the mixture, some 
hydrochloric acid is added to it; the acid hyposulphobenzoate of barytes crystal- 
lizes upon cooling. The free acid is obtained by precipitating the barytes of the 
last salt by sulphuric acid, filtering, evaporating the solution by the naked fire 
and finally in vacuo over sulphuric acid ; in this way the acid is obtained in a 
crystalline state. The crystals may be heated to 302° without alteration, but 
at a higher temperature they are decomposed. 

This acid forms both an acid and neutral class of salts, the first containing 
one atom of water and one atom of metallic oxide as base, the other two atoms 
of metallic oxide. All these salts when distilled with an excess of hydrate of 
potash leave a residue composed of sulphate and sulphite with carbonate of pot- 
ash, indicating the presence of hyposulphuric acid in the original compound. 
Acid hyposiilphobenzoale of barytes crystallizes in oblique rhomboidal prisms, 
soluble in 20 parts of cold water, and containing 9.6 per cent, of water of crys- 
tallization or 3 atoms, which it loses at 212°. 

Neutral hyposvlphobenzoate of baryfes, 2BaO-fC l4 H 4 3 ,S 2 5 ; is obtained 
by boiling the acid salt with carbonate of barytes ; it is more soluble than the 
former salt, but crystallizes with difficulty in a regular form. It will be observed 
that hyposulphobenzoic acid is formed by the abstraction of the elements of 1 
atom of water from 1 atom of benzoic acid and 2 atoms sulphuric acid, and that 
it retains the saturating power of 2 atoms of acid, being Dibasic. 

Nitrobenzoic or benzoenitric acid, HO-!- C , 4 H , O 3 ,N0 4 ; an acid formed by 
the abstraction of HO from the elements of nitric acid and benzoic acid. It is 
prepared by boiling benzoic acid with an excess of nitric acid, the first is dis- 
solved and colours the fluids red ; deutoxide of nitrogen is evolved as an acci- 
dental product arising from the action of the nitric acid on the nitrobenzoic acid 
already formed. From the cold solution crystals similar to benzoic acid are 
deposited; the fluid eventually becomes a solid crystalline mass. At 50°, 400 
parts of water dissolve 1 part of the acid, at 212° 10 parts. It dissolves easily 
in alcohol and ether; fuses at 260°.6 (127° centig.,) but begins to sublime at 
230° ; the pure acid sublimes unchanged ; chlorine has no action upon it. 

The nitrobenzoates are for the most part soluble in water and alcohol, crys- 
tallizable, explode by heating, and when gently warmed give off nitrobenzide 
(C 12 H 5 N0 4 .) Ammonia forms a neutral and acid salt. The salt of lime is 
acicular and contains 2 atoms of water, which are driven off at 374°. The salt 
of barytes loses 4 atoms of water at 212°. The salt of strontian loses 2| equi- 
valents of water at 266°. When acid nitrobenzoate of ammonia is added to a 
solution of sulphate of zinc, a gelatinous basic salt precipitates, containing 4 
atoms of oxide of zinc to 1 atom of acid. The filtered solution gives the neu- 
tral salt of zinc in crystalline plates, which contain 5 atoms of water. The salt 
of copper is a blue powder soluble in hot water, containing 1 atom of water. 
Besides a neutral nitrobenzoate of lead, a remarkable sub-salt exists, in which 
1 atom of oxide of lead is united with 5 atoms of the neutral salt. Nitroben- 
zoic acid forms fine crystallizable compounds with both oxide of ethyl and 
oxide of methyl. (Mulder, Mitscherlich.) 

Bromobenzoic acid, 2H04- C 2 8 H 9 Br0 8 ; a bibasic acid, discovered by Pel- 
igot, and formed by the action of 4 atoms of bromine upon 2 atoms of benzoate 
of silver : 



BENZOLE. 583 



C 3 -8 H i o°a + 2A £ and 4Br=C 2a H 9 Br0 8 and 2AgBr and HBr. 

When bromobenzoic acid is precipitated from its salts by a strong acid, the 
latter assumes the two atoms of water of the bromobenzoic acid, which is 
thrown down anhydrous. The bromobenzoates are in general crystallizable 
salts, that of the peroxide of iron is insoluble, and has the properties and 
appearance of the benzoate of iron. 



BENZOLE. 

i 

Syn. Benzin, benzene, phene. Formula C 12 H G . 

This compound, which is named benzole by Liebig, the termination oh being 
assigned to hydrocarbons, was originally obtained by Mr. Faraday from the 
condensed liquid of compressed oil gas and described under the name of bicar- 
buret of hydrogen ; more lately Mitscherlich found that it was the principal pro- 
duct formed on distilling benzoic acid with hydrate of lime, and named it ben- 
zin. It is formed by the abstraction of the elements of 2 atoms of carbonic acid 
from 1 atom of crystallized benzoic acid : 

C lv H 6 4 -C 2 4 =C 12 H 6 . 

Benzole is prepared by distilling 1 part of crystallized benzoic acid with 3 
parts of hydrate of lime; rectifying the oily product by a second distillation 
with water, or better from quicklime. It is a limpid colourless liquid, of a pe- 
culiar ethereal odour which is agreeable ; its density is 0.85 ; it boils at 186°.8 
(86° centig. ;) the density of its vapour is 2378, its combining measure 4 
volumes ; at 32° it becomes a crystalline mass, which becomes liquid at 44°.6 
(7° centig.) Benzole is insoluble in water, soluble in alcohol and ether. It is 
not decomposed by any hyd rated acid. 

Sulpliobenzide C, H 5 S0 3 (Mitscherlich.) Benzole like naphtaline affords 
several products when decomposed by acids. When exposed to the vapour of 
anhydrous sulphuric acid it forms a viscid liqnid, which dissolves entirely in a 
small quantity of water ; on adding a larger quantity of water, sulphobenzide falls 
as a precipitate, which, dissolved in ether, gives sulphobenzide crystallized, by 
evaporation. Sulphobenzide is a colourless substance, perfectly neutral ; it 
fuses at 212,° boils at a higher temperature and sublimes unchanged. In the 
formation of this substance 1 atom of anhydrous sulphuric acid and 1 atom of 
benzole abandon 1 atom of water : 

C 12 H 6 andS0 3 =C 12 H 5 S0 2 and HO. 

Ht/posulphobenzidic ucid, si/lphobenzinic acid, benzo sulphuric acid, HO, 
C 22 H 5 S 2 5 ; this acid remains in the liquid which deposites sulphobenzide. 
It is also produced on dissolving benzole in oil of vitriol, or in fuming sulphu- 
ric acid. It is a very acid liquid, which crystallizes, and resists a tempe- 
rature of 392°. It may be viewed as a compound of sulphobenzin with 
hydrated sulphuric acid. Hyposulphobenzidate of copper forms large regular 
crystals. (Mitscherlich.) 

N'urobenzide, C n H 5 N0 4 , a liquid compound obtained by dissolving ben- 
zole to saturation in hot concentrated nitric acid; on diluting the acid with 
water and allowing it to cool, the liquid separates and subsides to the bottom. 



584 BENZOLE. 

At 59° nitrobenzide is yellow, has a sweet taste and the odour of cinnamon. 
Its density is 1.209, that of its vapour 4294; it boils at 433.°4 (223° centig.,) 
crystallizes in needles at 37°. 4 (3° centig.) It is insoluble in water, soluble 
in alcohol and ether; dilute acids also dissolve it; alkalies do not decompose it. 
(Mitscherlich.) 

Azobenzide, C^ 2 H 5 N, a volatile, red, crystalline substance, obtained on 
distilling an alcoholic solution of nitrobenzide with dry hydrate of potash. It 
is fusible at 149°, and boils at 379°.4 (193° centig.) 

Chloride of benzole, C 12 H 6 C1 6 , a crystalline substance, obtained on ex- 
posing benzole to chlorine gas, in sunshine; 6 atoms of chlorine unite with 
the benzole without displacing any hydrogen. (Mitscherlich.) 

Chlorobenzide, C 12 H 3 C1 3 , an oily liquid, obtained by distilling chloride of 
benzole from hydrate of lime. It boils at 410°, its density is 1.157, that of 
its vapour 6370. 

Bromine forms analogous compounds with benzole. 

Benzone, Ci 3 H 5 0, one of the liquid products of the distillation of crys- 
tallized benzoate of lime: 

1 at. of benzone .... C 13 H 5 

1 at. of carbonic acid C 2 

1 at. of lime CaO. 



1. at. of benzoate of lime C 14 H 5 3 -j-CaO. 

The crude product of the distillation contains also benzole and naphtaline, 
of the first of which it is divested by heating it on a water-bath, and keeping 
it for a sufficient time at 392°, and of the second by exposing the liquid thus 
obtained to, a cold of— 4°, when naphtaline separates. Benzone is oily and 
viscid; not altered by nitric acid and hydrate of potash, but decomposed by 
chlorine and sulphuric acid. (Peligot.) 



PRODUCTS OF THE DECOMPOSITION OF HYDRURET OF BENZOYL, 

Hydrobenzamide, C 42 H l3 N 2 , or C l4 H 6 N§. Hydruret of benzole is acted 
upon when mixed with twenty times its volume of a concentrated solution 
of ammonia in a vessel hermetically sealed, and kept for several hours at a 
temperature of 104° to 122° (40 to 50° centig.; A crystalline mass of hydro- 
benzamide is formed, which may be purified from the oil by washing with 
cold ether, in which hydrobenzamide is insoluble, dissolving the residue in 
alcohol, and evaporating at the usual temperature, when hydrobenzamide is 
obtained in regular crystals. They are colourless octohedrons or rhomboidai 
prisms, which enter into fusion at 230°, and are decomposed by dry distilla- 
tion leaving a residue of charcoal. The alcoholic solution is converted by 
boiling into ammonia and hydruret of benzoyl. This substance is formed by 
the abstraction of the elements of 6 atoms of water from 3 atoms of hydruret 
of benzoyl and 2 atoms of ammonia (Laurent:) 

3(C 14 H 6 2 ) and 2NH 3 = C 42 H 18 N 2 and 6HO. 

The whole oxygen of the oil and whole hydrogen of the ammonia separate 
as water; the formation of this substance is, therefore, different from that of 
an ordinary amide. It is, indeed, simply a dydruret of benzoyl, in which the 
2 atoms of oxygen are replaced by N* . 



BENZOYL. 585 

Benzhydramide, a crystalline substance, isomeric with hydrobenzamide, 
Azobenzoi'le, C 42 H 15 N 2 , or C 14 H 5 H|; a white crystalline powder soluble in 
alcohol. Benzoilic azotide, C 14 H.N, a white, insipid, crystalline powder, in- 
soluble in boiling alcohol. These three bodies were derived by Laurent from a 
yellow resinous mass, which is formed by the action of solution of ammonia, 
upon the crude essence of bitter almonds of commerce. 

Hydruret of Sulphobenzoyle, C 14 H^S 2 -fH; a body representing the hy- 
druret of benzoyl, of which the 2 atoms of oxygen of the benzoyl are replaced 
by 2 atoms of sulphur. M. Laurent has generally succeeded in preparing this 
compound by dissolving 1 volume of the crude essence of bitter almonds in 8 
or 10 volumes of alcohol, and then adding gradually 1 volume of sulphuret of 
ammonium. The liquor becomes turbid in a few minutes and allows a white 
powder to fall similar to farina. By throwing this on a filter, and washing it 
several times with boiling alcohol, the hydruret of sulphobenzoyle is usually ob- 
tained pure. It is white, pulverulent, and composed of small rounded grains, 
like those of starch, without a trace of crystallization. Although apparently 
inodorous, it communicates a highly disagreeable odour to the hands. It is insolu- 
ble in water and alcohol, slightly soluble in ether. It is slowly decomposed by 
an alcoholic solution of potash* 

Hydruret of sulphazobenzoyfe, a crystalline compound formed by dissolving 
essence of bitter almonds in 4 or 5 volumes of ether, adding to it 1 volume of 
sulphuret of ammonium, and leaving the whole for fifteen days or a month. It 
forms a white crystalline crust, which it is necessary to dissolve and crystal- 
lize from ether to purify it. Its analysis represents a compound of 6 atoms of 
hydruret of sulphobenzoyl with 1 atom of hydrobenzamide : 

6(C 14 H 5 S 2 +H)+C 42 H l8 N 2 . 

Other views may be taken of the constitution of this substance. On the 
theory upon which it is named by Laurent, it is benzoyl in which the two equiva- 
lents of oxygen are replaced by two equivalents made up of sulphur and nitrogen : 

C 14 H 5 S'N i+ H. 

Or, multiplying the preceding formula by three, as 2 atoms of hydruret of sul- 
phobenzoyl, and 1 atom of hydruret of azobenzoyl : 

2(C l4 H 5 S 2 -fH) + (C 14 H 5 N.+H.) 

In these formula, Ni is made equivalent to S or O, an opinion which M. Laurent 
has long maintained. 

Benziniide, C 2 3 H t jN0 4 , a substance discovered by Laurent in crude essence 
of bitter almonds. It crystallizes in white needles, which have a pearly lustre 
and are very light. 



ISOMERIC COMPOUNDS OF BENZOYL. 

Benzoin?, C 14 H 6 2 , a crystalline substance, having the same composition 
as hydruret of benzoyl, into which the latter is often converted in a manner 
that is not understood. It is never produced in the pure hydruret of benzoyl, 
but is formed in the essence, which contains hydrocyanic acid, by the presence 
of alkalies, sulphuret of sodium and cyanide of potassium. The essence may 
be converted entirely into benzoine, by mixing it with an equal volume of a so. 



* Sur de Nouvelles combinaisons benzo'iliques azolees et sulphurees ; par M. Laurent.- 
Annales de Chimie, &c, 3rae Serie, tome 1, p. 292. 



586 SYNAPTASE. 

hition of potash in alcohol kept cold. It is purified by "repeated crystallizations 
from alcohol. 

BenzoYne crystallizes in colourless prisms of high lustre, is inodorous, taste- 
less, fuses at 248°, and distils at a higher temperature without being modified. 
It is slightly soluble in hot water, but insoluble in cold, more soluble in hot than 
cold alcohol. 

Hydrobenzoi'narnide, a white powder, obtained by treating benzoYne with 
solution of ammonia at a gentle heat, isomeric with hydrobenzamide (Laurent.) 

Benzile C 14 H.0 2 ,a substance which crystallizes in regular six-sided prisms, 
of a rhombic base, and sulphur yellow colour ; formed by passing a stream of 
chlorine gas through fused benzoYne, so long as hydrochloric acid is disengaged. 
It is inodorous, tasteless, fuses between 194 and 197 c (90 and 92° cent.) May 
be distilled, or dissolved in concentrated sulphuric acid without change. The 
aqueous solution of potash has no effect upon it, but the alcoholic solution con- 
verts it into benzilic acid (Laurent.) 

Benzilic acid, HO-fC 2 8 H , , 5 ; may be separated from benzilate of potash 
by an excess of hydrochloric acid. The acid crystallizes on cooling, in colour- 
less rhombohedrons, of high lustre, or in long prismatic needles. It fuses at 
248°, and is decomposed at a higher temperature, giving a sublimate of ben- 
zoic acid, accompanied by violet vapours, and a residue of carbon. It forms 
a lively crimson solution in cold oil of vitriol. Benzilic acid contains the ele- 
ments of 2 atoms of benzile and 2 atoms of water, one of which remains 
basic to the acid, and is replaced in the benzilates by a metallic oxide. Ben- 
zilate of potash forms large limpid crystals, soluble in water and alcohol. 
(Liebig.) 

Azobenzoi'de, C 42 H 16 iN 2 i; a white pulverulent substance, described by 
Laurent, but of which the composition is rather doubtful. 

Cyanobenzile, a substance which is deposited in transparent, voluminous 
crystals, when to an alcoholic solution of benzile, one third of its bulk of very 
concentrated hydrocyanic acid is added, and the whole gently heated. (Vou 
Zinin.) 



SYNAPTASE. 

The white of both sweet and bitter almonds consists, in a great measure, of 
a peculiar matter, very soluble in water, which was named synaptase by M. 
Robiquet. To prepare it, he directed sweet almonds, from which all the fat 
oil has been expressed, to be mixed intimately with twice their weight of wa- 
ter, allowed to macerate thus for two hours, and then to be submitted to pres- 
sure, which is uniformly increased. The filtered liquid contains vegetable al- 
bumen, which is thrown down by acetic acid, and gum, which is precipitated 
by acetate of lead. A liquid remains, which contains some free acetic acid, 
acetate of lead, sugar and synaptase; the lead is thrown down by sulphuretted hy- 
drogen, and the synaptase by alcohol, while the free acid and sugar remain in 
solution. The precipitated synaptase is washed with alcohol, and dried in 
vacuo over sulphuric acid. 

Dry synaptase is described as a yellowish white, opaque, horny mass, hard 
and friable; very soluble in cold water. In a fresh solution, iodine produces 
a deep rose colour, without any precipitate. The solution of synaptase does 
not keep, but soon becomes turbid from the formation of a white precipitate, 
and acquires a mouldy odour. It is precipitated from solution by alcohol, in 
flocks, which redissolve in an excess of water. Acids do not produce a pre- 
cipitate in its solution; at 140° it coagulates like albumen. It contains azote, 



49.025 


48.555 


7.788 


7.677 


24.277 


25.026 


18.910 


18.742 



SYNAPTASE. 587 

and produces ammonia and a new acid in boiling solutions of the alkalies. 
The composition of synaptase has not been determined. 

A matter which, if a pure substance, is probably the same was obtained by 
Liebig and Woshler, and named emulsin, by treating an emulsion of sweet al- 
monds with ether, to take up all the fat oil, and then precipitating the trans- 
parent, syrupy liquid which remained, by alcohol, a white matter was abun- 
dantly thrown down, which formed, when dry, a horny, semi-transparent 
mass. This substance gives much ammonia when boiled with a solution of 
barytes or a caustic alkali. There are no means of determining the atomic 
composition of emulsin, but the following are the results of two analyses of it 
by Dr. R. D. Thomson and Mr. Richardson: 

Carbon .... 

Hydrogen .... 

Oxygen .... 

Nitrogen . 

100.000 100.000 

The reaction which occurs when synaptase and the amygdalin of bitter al- 
monds meet each other in solution is very remarkable, and a knowledge of it 
necessary to enable us to form a conception of the phenomena of the distilla- 
tion of the bitter almond. I shall state here the latest view of it which has 
been taken by M. Liebig. On mixing a solution of 10 parts of amygdalin in 
100 parts of water, with a solution of 1 part of synaptase in 10 parts of 
water, a particular decomposition immediately takes place; the mixture 
becomes opalescent without losing its transparency; acquires the odour of 
bitter almonds, and gives on distillation hydrocyanic acid and hydruret of 
benzoyl with the vapour of water. The residue is rendered turbid by coagu- 
lated synaptase, and on continuing the evaporation, a very sweet liquid is ob- 
tained, which contains crystallizable sugar. After destroying the sugar by fer- 
mentation, a fixed acid remains in the residue. The quantity of sugar obtained 
is more considerable than what the elements of the amygdalin could produce; 
it would appear, therefore, that the elements of the synaptase contribute to its 
formation. The decomposition is not complete unless the amygdalin and sy- 
naptase are dissolved in a proper quantity of water; if it is insufficient to dis- 
solve the hydruret of benzoyl liberated, a corresponding quantity of amygdalin 
remains undecomposed. (Traite, p. 276.) 

The constituents of the bitter almond are the fixed oil, which is separated by 
expression, and the synaptase and amygdalin, the two last in such a condition 
that they cannot re-act upon each other. When the almond cake is treated 
with boiling alcohol, the amygdalin is dissolved out, and the synaptase coagu- 
lated. When the cake is moistened with water, the odour of hydrocyanic acid, 
and of the essence are immediately perceived, but the cake must be diffused 
through a certain quantity of water, in order that the mutual action of the 
synaptase and amygdalin may be complete, and that the whole of the last may 
disappear. In preparing the distilled wafer of bitter almonds of pharmacy, M. 
Liebig recommends that a mixture of 1 part of the cake and 20 parts of luke- 
warm water be made, and left to itself for twenty-four hours before submitting 
it to distillation. 

One atom of amygdalin contains the elements of (Liebig:) 

1 equiv. of hydrocyanic acid . . C 2 H N 

2 equiv. of hydruret of benzoyl . C 28 H l2 O^ 
2 equiv. of sugar C 6 H 3 5 



588 CINNAMYL. 

2 equiv. of formic acid . . . . C 4 H 2 6 
7 equiv. of water H 7 7 



1 equiv. of amygdalin .... C 40 H 27 NO 22 

One hundred parts of amygdalin are said to yield 47 parts of the crude 
essence of bitter almonds, and these 47 parts to contain 5.9 parts of free hydro- 
cyanic acid. The last acid is not indicated by nitrate of silver added to a solu- 
tion of the crude essence in water, owing to the presence of the oil ; to obtain 
a precipitate of cyanide of silver, ammonia-nitrate of silver must be used, and 
the ammonia saturated with nitric acid, after the lapse of some time. 

Laurel-water is prepared by distilling with water 2 parts of fresh leaves of 
the prunus laurocerasus, of which the three first portions are received ; the pro- 
duct contains the same elements as the water of bitter almonds. The leaves 
contain amygdalin and another substance, which appears to act upon it when 
distilled with water, in a manner analogous to synaptase. 



CHAPTER V. 



ESSENCE OP CINNAMON AND BODIES DERIVED FROM IT. 



CINNAMYL SERIES OF COMPOUNDS. 

Cinnatnyl, C x 8 H 7 2 a=Ci; the hypothetical radical of the essence of cinnamon 
and of cinnamic acid. 

Essence or oil of cinnamon.— According to the recent determinations of M. 
Mulder, C 20 H n O is the formula for oil of cinnamon derived from the cinnamon 
of Ceylon, of Java and China, and of the flowers or bark of the cassia-tree. 
This essence absorbs oxygen from the air, and forms cinnamic acid, two differ- 
ent resins and a new oil C 13 H 3 2 , which appears to be the substance examined, 
and considered as oil of cinnamon by MM. Dumas and Peligot. The two 
resins have the composition C 30 H, s O 4 and C 24 H 10 O 2 . 

This oil is obtained by distilling with water the bark of the Laiirus einna- 
momum, or the flowers and bark of the cassia. It is yellow, becoming brown 
in air, with the odour of cinnamon, and a sweet and burning taste, its density 
1.008 at 77°, boiling point 428° ; it becomes solid at 23°. It is slightly soluble 
in water, and the solution produces with iodine and iodide of potassium, reddish 
brown crystals, of a metallic lustre, containing, according to Dr. Apjohn, Kl-f 6 
(CiHJ.) The oil dissolves completely in potash, and affords on distillation an 
oil, lighter than water C 13 H 10 2 , while the residue contains cinnamate of pot- 
ash, and a black matter (Mulder.) The bleaching chlorides convert essence of 
cinnamon into benzoic acid. 

Cinnamic achl, HO -fC 18 H 7 3 =HO + CiO. This acid is formed by the 
oxidation of the essence of cinnamon in air, or by dissolving the oil of the bal- 

* Journal de Pharmacie, t. 26, p* 549* 



CINNAMIC ACID. 589 

sam of Pern in an alcoholic solution of potash, evaporating to dryness, dissolving 
the residue of cinnamate of potash in boiling water, and liberating the cinnamic 
acid by an excess of hydrochloric acid.* The cinnamic acid crystallizes on 
cooling in tufts of crystals, which are colourless, and have an aromatic and 
very acrid taste. The crystals fuse at 264°.2 (129 °centig.) enter into ebulli- 
tion at 554°, and distil over as a heavy oil, which fixes on cooling; they sublime 
at a lower temperature. Cinnamic acid is less soluble both in cold and hot 
water, than benzoic acid, which it considerably resembles ; very soluble in alco- 
hol and ether; from alcohol it crystallizes in large rhomboidal prisms, which are 
hard and very friable. It may be distinguished from benzoic acid by nitric acid, 
which converts it into hydruret of benzoyl and nitro-cinnamic acid ; cinnamic 
acid also does not combine with sulphuric acid as benzoic acid does. The 
salts of cinnamic acid are monobasic, and have a great analogy to the benzo- 
ates. (Dumas and Peligot, Mulder.) 

NUro-cinna>hic acid, HO + Cj 8 H 6 O v N0 4 ; produced by the abstraction of 
HO from the elements of cinnamic acid and nitric acid. This acid is prepared 
by adding cinnamic acid in powder to strong nitric acid, preventing the tem- 
perature from rising above 140°. The cinnamic acid is at first dissolved ; the 
mixture soon becomes hot, and a crystalline substance separates; the latter is 
washed with water, dissolved and crystallized from alcohol. Nitrocinnamic 
acid is white with a shade of yellow, fuses at 518° ; heated above that tempera- 
ture, it boils and is decomposed. This acid is almost insoluble in boiling wa- 
ter : it is also but sparingly soluble in alcohol requiring 372 parts of alcohol to 
dissolve it at 68°, while cinnamic acid is soluble in 4.2 parts, benzoic acid in 
1.96, and nitrobenzoic acid in somewhat less than its own weight. 

The alkaline nitrocimiamate* dissolves easily in water; the other salts are either 
soluble with difficulty or entirely insoluble; they explode when heated. The 
ether of this acid is formed by heating the latter with 20 parts of alcohol and 
a little sulphuric acid for several hours, at a temperature not exceeding 176°. 
The acid is dissolved, and the liquid on cooling deposits the nitrocinnamate 
of oxide of ethyl in prismatic crystals. This ether melts at 276°.8 (136° cen- 
tig.,) and boils at 572° but is then partly decomposed ; it is not decomposed by 
ammonia. 

When more than 1 part of cinnamic acid is added to 8 parts of nitric acid, 
the temperature rises above 140°, and nitrobsnzoic acid is formed, with another 
acid not yet examined. (Mitscherlich.) 

Hydruret of cinnamyl, C l3 H rt 2 =CiH; an oily liquid obtained on ad- 
ding water to the nitrate of hydruret of cinnamyl; discovered by Dumas and 
Peligot. 

Nitrate of hydruret of cinnamyl, C, 8 H 3 2 -f HO,N0 5 ; a compound formed 
on treating the essence of cinnamon of China, with concentrated and colourless 
nitric acid. The crystals first obtained are purified by pressure in paper, and 
afterwards crystallized from alcohol ; it forms long oblique rhomboidal prisms, 
perfectly pure and colourless. This compound soon alters by keeping, disen- 
gaging nitrous acid and the hydruret of benzoyl; this decomposition is hastened 
by heating the compound slightly. 

Chlorodnnose, C 1 8 H 4 CI 4 2 . — This name is given by Dumas and Peligot 

[* This acid may be prepared more economically by distilling' pure balsam of Tolu. Sub- 
jected to heat balsam of Tolu fuses and a little water and volatile oil first come over; these 
are succeeded by the acid, in the form of a heavy oil condensing in the cool part of the 
neck of the retort, into a white crystalline mass. — Mr. G. Heaver, Ann. of Chim. and 
Pract. Pharm. 

Cinnamic acid taken internally undergoes the same change in the system, as benzoic 
acid (page 581,) being converted into hippuric acid. — Erdmand and Marchand, Jouro., iiir 
Prakt. Chem. t. xxv. R. B.] 

50 



590 SALICIN. 

to a chlorinated product of the essence of cinnamon. It is a volatile solid com* 
pound, crystalline and colourless at the usual temperature, which enters into 
fusion at a moderate heat and sublimes without residue. It is neither altered 
by concentrated sulphuric acid nor by gaseous ammonia. 

Oil of the balsam of Peru. — This oil is obtained by treating 2 volumes of 
the balsam with 3 volumes of a solution of caustic potash of density 1.3, and 
floats over a dark watery fluid (Stoltz and Wernher.) It is purified by distil- 
lation. This oil is termed cinnameine by M. Fremy. When boiled with an 
alkali it is transformed into cinnamic acid, and an indifferent substance to which 
Fremy has applied the name peruvine. This last is an oily colourless liquid 
lighter than water; its composition is expressed by C 1 8 H 12 2 . Fremy finds 
the balsam of Tolu to contain the same bodies as the balsam of Peru. Ac- 
cording to Richter, the balsam of Peru contains two different oils, one of which 
is soluble in alcohol of 75 per cent, and is called by him my 'Ho spermine, the 
other oil which is insoluble he names myroxiline. On treating the first with an 
alcoholic solution of potash, an acid is formed different in its capacity of satura- 
tion, according to Richter, from cinnamic acid, and which he names myriosper* 
mic acid. Its atomic weight deduced from the salt of silver is 1553.85. 



CHAPTER VI. 



SALICIN AND BODIES OBTAINED FROM ITS DECOMPOSITION. 



SECTION I. 



SALICIN. 

Formula: C 42 H 29 22 ±=C 42 H 23 16 -}-6H0? (Mulder.) 
This neutral crystallizable substance was discovered by Buchner and Leroux 
in the bark of the Salix helix. It is contained in the bark and leaves of all the 
species of willow which have a bitter taste, and in some poplars. To prepare 
salicin the fresh bark or dry ground bark is boiled with water till a strong 
decoction is made ; to the concentrated and boiHng decoction oxide of lead is 
gradually added till the liquid is colourless. Gum, tannin and all extractive 
matters which may interfere with the crystallization of the salicin are thus car- 
ried down by the oxide of lead. The oxide of lead dissolved is then removed 
first by means of sulphuric acid, and then by sulphuret of barium. The liquid 
is crystallized by evaporation and the salicin made perfectly white by the use 
of charcoal and repeated crystallizations. The sulphuret of lead which is pre- 
cipitated in the process also assists as a decolorizing agent. The barks which 
contain much salicin yield it at once in crystals, when they are exhausted by 
cold water and the extract evaporated with caution, according to Merck. 

Salicin crystallizes in delicate colourless needles of a silky lustre, which have 
a bitter taste, and no action on vegetable colours. It is persistent in air, loses 
nothing at 212°, fuses at 248°, and is decomposed by a higher temperature. 



SALICYL. 591 

Salicin is soluble in 5 or 6 times its weight of cold water, in much less boiling 
water, is very soluble in alcohol, but insoluble in ether and oil of turpentine. It 
dissolves purple red in concentrated sulphuric acid, a property by which it may 
be recognised even in the dry bark, the latter being stained red by sulphuric 
acid when it contains salicin. 

Salicin does not combine with acids, nor possess alkaline properties. It is 
thrown down by the ammoniacal acetate of lead as a white precipitate, in which 
according to Piria 6 atoms of water belonging to salicin are replaced by 6 atoms 
of oxide of lead ; but according to Ettling, the quantity of oxide of lead is not 
constant but increases with the washings to which the precipitate is submitted. 

Saliretin, C 30 H 15 O 7 -|-HO. — When raised to the boiling point with dilute 
sulphuric or hydrochloric acid, the solution of salicin soon becomes turbid, and 
allows a yellowish substance to fall having the consistence of a resin, which is 
saliretin. When prepared with concentrated acids, the product wants the atom 
of water represented in the formula, or is anhydrous. In this decomposition 1 
atom of hydrated salicin is resolved into 1 atom of saliretin and 1 atom of grape 
sugar, which last is found in solution. 

Saliretin is insoluble in water, and precipitated by that liquid from its solution 
in alcohol, in ether or concentrated acetic acid, in all of which it is very soluble. 
It is not soluble in ammonia, but is dissolved by the fixed alkalies and precipi- 
tated from them by acids. Saliretin is coloured blood-red by concentrated 
sulphuric acid; by nitric acid it is converted into carbazotic acid. (Piria.) 

Chlorinated salicin, chlorosalicin. — Two compounds have been obtained by 
treating a solution of salicin by chlorine, one a crystalline yellow powder, C 40 
H 25 C1 4 22 , produced at the ordinary temperature; the other formed about 
140°, a red oily liquid, C 42 H 13 C1 7 18 . 

Rutilin. — This name is applied by Braconnot to the product of the decom- 
position of salicin by sulphuric acid. Alkalies change its tint to a deep 
purple. 



SECTION II. 



SALICYL SERIES OF COMPOUNDS. 

Salicyl, C I4 H 5 4 = Sa; the hypothetical radical of salicylous acid, salicy- 
lic acid and some other compounds: equivalent to benzoyl plus 2 atoms of 
oxygen.* 

Salicylous acid, spiroi'lhydric acid, H-f C, 4 H.0 4 = H,Sa. This substance 
was obtained by M. Piria by distilling salicin with dilute sulphuric acid and 
bichromate of potash, and has been shown by Dumas and by Ettling to be the 
principal constituent of the oil obtained by Pagenstecher by distilling the 

* The name salicyl was applied by Dumas and Piria to this hypothetical radical, which 
was viewed as a higher degree of oxidation of benzoyl. The oil of spiraea ulmaria, or 
salicylous acid, is represented as the hydruret of this radical, which also exists in combi- 
nation with potassium, &c, in the salicylites. An objection to and source of some con- 
fusion attending- this view is that it represents salicyl as a salt radical or halogen body, 
combining directly with metals, and not as a basyle, like benzoyl, ethyl, and the other 
'radicals with which it is associated. 

M. Liebig points to an explanation of the isomerism of salicylous and benzoic acids and 
their salts, in the circumstance that while benzoic acid is monobasic, salicylous acid may 
have its equivalent multiplied by 2 or by 3, and be a bibasic or a tribasic acid. This 
supposition, however, is not supported by the density of salicylous acid in the state of va- 
pour, which is the same as that of benzoic acid. 



592 SALICYL. 

flowers of the Queen of the meadow (spiraea vlmaria,) and which M. Loewig 
had analyzed and described under the name of spiroilhydric acid. 

The proportions lately recommended by Dr. Ettling for preparing salicy- 
lous acid from salicin are: 

3 parts of salicin 

3 parts of bichromate of potash 

4| parts of concentrated sulphuric acid 

36 parts of water. 
The bichromate of potash and salicin are intimately mixed, and after pour- 
ing over them two-thirds of the water, the whole being well agitated in the 
retort, we add all at once the sulphuric acid previously diluted with the re- 
maining third of the water, and agitate again. A feeble reaction slowly mani- 
fests itself, accompanied by a slight disengagement of gas, which lasts about 
half an hour or perhaps three quarters of an hour, when an ounce is employed 
for each part ordered; at the same time the liquid assumes an emerald tint and 
becomes warm. As soon as that reaction has ceased, the retort is placed upon 
the fire and moderately heated. The water vapour carries over the salicy- 
lous acid, which separates after some time. It is purified by washing it with 
water and rectifying from chloride of calcium. From half a pound of salicin 
Dr. Ettling obtained two ounces of the oil.* 

Salicylous acid is an oily inflammable liquid, colourless or slightly yellow, 
having a burning taste, and agreeable aromatic odour; of density 1.1731, be- 
coming solid at — 4° (Loewig;) it boils at 385°. 7 (196°.5 centig.) when pre- 
pared from salicin (Piria,) while the oil from the flowers of Spiraea boils at 
359°. 6 (182° centig.,) according to Ettling. The density of its vapour is by 
observation 4276; by calculation 4260, or the same as that of benzoic acid. 
It dissolves easily in water, and may be mixed with alcohol and ether in all 
proportions; its solution in water reddens tincture of litmus, and discolours it 
after the lapse of some time. It is decomposed by sulphuric acid; also by 
chlorine, one atom of hydrochloric acid being formed and eliminated, and one 
atom of chlorine substituted for the hydrogen, as usual. When heated with 
an excess of hydrate of potash, salicylous acid is converted into salicylate of 
potash, with an escape of hydrogen gas. Potassium also when slightly 
heated in it, gives the same products. 

Salicylous acid is recognised by producing a violet colour with salts of per- 
oxide of iron, which disappears after some time. In the sa/icylites, the atom 
of hydrogen of the formula of salicylous acid is replaced by a metal. The 
salts of the fixed alkalies and ammonia are described as soluble and possessing 
an alkaline reaction, all the others as insoluble; most of them as yellow and 
containing water of crystallization. The salts of lead and copper are anhy- 
drous. The neutral salt of soda contains 2 atoms of water which it loses at 
248°, the salt of barytes contains 2 atoms of water. They are all decom- 
posed by strong acids, and salicylous acid set at liberty. Dr. Ettling describes 
an acid salt or bisalicylite of potash having the same composition as the biben- 
zoate of potash; also a corresponding salt of soda, both of which form colour- 
less acicular crystals. 

Salicylimide, salhydramide'C 42 H ] 8 6 N 2 . This body is prepared by dis- 
solving salicylous acid in three or four times its volume of cold alcohol, and 
adding a quantity of aqueous solution of ammonia, equal to that of the salicyl- 
ous acid employed. Yellowish-white needles are immediately produced, and 
the liquid soon becomes a solid mass. By a gentle heat the whole is re-dis- 
solved and crystals of salicylimide are deposited on cooling. This body is in- 



I T 



^iebig's Annalen xxxv, 241 ; or Annales de chitnic, &c., 3me Serie, t. 1. p. 490. 



SALICYLIC ACID. 593 

soluble in water; it is soluble in 50 parts of boiling alcohol, but v ery slightly- 
soluble in cold alcohol; its solution has a strong alkaline reaction. Solutions 
of alkalies and acids act upon salicylimide, with the aid of heat, as they do 
upon amides, reviving the ammonia and acid. 

In the formation of this compound 3 atoms of salicylous acid unite with 2 
atoms of ammonia, while 6 atoms of water containing all the h ydrogen of the 
ammonia are abandoned; 2 atoms of nitrogen are thus substitu ted for 6 atoms 
of oxygen, in the formation of salicylimide. It may be represented as 3HO+ 

^42^ 15 tvt 3 or dividing by three: 

HO+C 14 H 5 ° f 

Salhydramidide of copper, C 1 H 6 N0 2 Cu; or I^C^H^NO-f CuO. This 
remarkable compound is represented in the last formula as a salicylous acid, 
in which 3 atoms of oxygen of the salicyl are replaced by 1 atom of nitrogen, 
and this is combined with 1 atom of oxide of copper. It is obtained in a state 
of purity on mixing a solution of salhydramide, the preceding compound, very 
dilute and slightly cooled^ with the ammoniacal acetate of copper. The liquid 
immediately assumes an emerald green colour, and soon deposites very bril- 
liant plates of the same colour while at the same time the liquid becomes co- 
lourless. When this salt is heated with concentrated acids, it gives a salt of 
copper and an ammoniacal salt, while the hydrated salicylous acid is set at 
liberty. Potash ley does not decompose this salt except imperfectly; sulphu- 
retted hydrogen not more completely, even after one or two hours' action. If, 
however, it has first been made to boil with an acid, the decomposition by sul- 
phuretted hydrogen is instantaneous. 

Salhydramidide of iron, (311,0, ,H 5 NO)+Fe„O v This compound, 
which Dr. Ettling succeeded in forming, is analogous in composition to the 
copper compound. It precipitates in red flocks, which gradually acquire some 
lustre, becoming granular. Hydrochloric acid does not alter it in the cold, 
but when the acid is pretty concentrated and assisted with heat the compound 
is dissolved and salicylous acid separated. 

Salhydramidide of lead. There appear to be two compounds of salhy- 
dramide with oxide of lead, but they have not been obtained in a state of pu- 
rity. 

Melanic acid (anhydrous,) C , H 4 O 5 . Salicylile of potash exposed in a 
humid state to air absorbs oxygen and undergoes decomposition, becoming first 
green then black. The only products are acetate of potash and an insoluble 
black powder resembling lampblack, which Piria terms melanic acid. This 
acid contains no water of combination; it is soluble in alcohol and ether, and 
very soluble in alkalies. 

Salicylic acid, HO-f-C, 4 H,0 5 = HO,SaO. This acid is produced by 
heating salicylous acid with an excess of dry hydrate of potash, till the brown 
mass becomes white, which is attended Avith the escape of hydrogen gas. 
The salicylic acid is liberated by adding an excess of hydrochloric acid, and is 
purified by repeated crystallizations. This acid crystallizes both from solution 
and sublimation very much like benzoic acid. It may be volatilized without 
decomposition. It is sparingly soluble in cold water, very soluble in hot wa- 
water and in alcohol. It reddens vegetable colours and decomposes the alka- 
line carbonates. Salicylate of silver is an insoluble white precipitate, anhy- 
drous. (Piria.) 

Chloro salicylic acid, chloride of salicyl, chloride of spiro'ile; C l4 H 5 4 ,Cl. 
This compound is formed by passing a current of dry chlorine through dry 

50* 



594 OIL GAULTHERIA. 

salicylous acid. It crystallizes in yellowish oblique rhomboidal tables of a 
pearly lustre and peculiar aromatic odour. It fuses and sublimes unaltered. 
It combines directly with the alkalies, and is precipitated from these combina- 
tions by acids without undergoing the smallest change. This acid itself has 
been compared with the chlorochromic, and these salts viewed as salicylates 
of metallic chlorides. 

Chlorosalicylimide, ch/orosamide, C 42 H l5 Cl 3 6 N 2 ; is salicylimide in 
which 3. atoms of hydrogen are replaced by 3 atoms of chlorine. It is a yel- 
low mass insoluble in water, formed by directing a current of ammoniacal gas 
upon chlorosalicylic acid, so long as water is disengaged. 

Corresponding bromosa/icylic and in do salicylic acids exist, which undergo 
the same transformations with ammonia. 

Nilrosalicylic acid, spiroi'lic acid (Loewig;) C 14 H 5 3 N. Fuming nitric 
acid has a violent action upon salicylous acid, nitrous fumes are abundantly 
evolved,, with the formation of a dark yellow mass, which volatilizes when 
distilled with water; this matter has not been analyzed. When, on the other 
hand, nitric acid of ordinary strength is digested upon salicylous acid, per- 
oxide of nitrogen is evolved, and a crystalline mass remains, which may be 
purified by washing it with water and then dissolving it in alcohol. Nitro- 
salicylic acid crystallizes in small yellow prisms, the alcoholic solution of 
which dyes the skin and nails yellow; it forms crystallizable salts with the 
alkalies, ammonia produces with it a deep blood-red colour; with the perchlo- 
ride of iron it assumes a cherry-red tint. Its salts have not been sufficiently 
examined; their probable formula is MO-f-C, 4 H 4 3 ,N0 4 . 



OIL OF GAULTHERIA AND BODIES DERIVED FROM IT. 

[From the observations of Mr. William Procter, jr.,* it appears that the oil 
of gaultheria contains an acid analogous to salicylous acid and capable of 
yielding a series of compounds resembling those produced from the oil of spi- 
rea ulmaria. The oil of gaultheria resembles salicylous acid, it is an oily in- 
flammable liquid, having an aromatic and burning taste, of density 1.173, it 
boils at 412, slightly soluble in water, miscible with alcohol and ether in all 
proportions, it is decomposed by sulphuric acid, also by chlorine and iodine, 
hydrochloric and hydriodic acids being evolved. Dropped into a concentrated 
solution of potassa, it instantly solidifies, and separates from the solution as a 
white mass. 

Oil of gaultheria unites with the alkalies, and forms crystallizable compounds. 
These compounds are decomposed by acid and the oil set free. Their solutions 
when boiled are decomposed, the new compound yielding a crystallizable de- 
posite, on the addition of an acid, without any trace of oil. This deposite 
when heated sublimes without residue, and condenses in four-sided prisms, 
dissolved in hot water, it produces a fine purple colour with the salts of the 
protoxide of iron. 

Oil of gaultheria also combines with metallic oxides. • 
Heated with an excess of potassa, the oil is decomposed, hydrogen is given 
off, and the whole becomes a crystalline mass on cooling, the mass dissolved 
in hot water and decomposed by dilute hydrochloric acid yields a crystalline 
precipitate, having all the properties of an acid, it fuses at 250, and at a 
higher temperature sublimes unchanged. Its solution forms with the salts of 
iron a fine purple. The solution of its potassa salts is precipitated by soluble 
salts of silver, lead and tin, but not by those of baryta, zinc, copper, or iron, 

* Am. Journ. of Pharmacy, vol 14 p. 211, Oct. 1842. 



PHLORIDZIN. 595 

The protosalts of iron produce a deep red colour. When oil of gaultheria is 
acted on by chlorine, hydrochloric acid is evolved and a compound produced 
having many resemblances to chlorosalicylie acid, but this does not produce 
with ammonia a compound with all the properties of chlorosalicylimide. 

Nitric acid exercises on the oil an action similar to that, on salicylous acid. 

These compounds have not been subjected to ultimate analysis, without 
which the identity or difference of oil of spirea and gaultheria cannot be de- 
cided on. R. B.] 



SECTION III. 



PHLORIDZIN AND THE BODIES DERIVED FROM IT. 

Formula, C 42 H 2g 24 = C^H^O, 8 -j-6HO, according to Mulder, Erd- 
mann, Otto. But C 32 H 15 1 , + 6HO, and when dried, C 32 H 15 0, 2 + 3HO, 

according to Stass. 

This substance which very much resembles salicin, was discovered by De 
Kceninck and Stass in the bark of the root of the apple, pear, cherry, and 
plum tree. It has been considered as crystallized salicin plus 2 atoms of oxy- 
gen. It is extracted. from the bark cut into small pieces, by digestion in alco- 
hol of 80 per cent, at 176°. It is crystallized by distillation of the alcohol 
solution and cooling, and purified by means of animal charcoal. 

Phloridzin crystallizes in colourless silky prisms of a square base, of density 
1.4298, which are neutral, having a bitter astringent taste, are soluble in 100*0 
parts of cold water, and in all proportions in hot water, are soluble in alcohol 
and almost insoluble in ether. Phloridzin loses 4 atoms of water of crystalli- 
zation at 212°, fuses at 320°, and is not decomposed below 392° (200° centig.) 
It produces a white precipitate in solution of subacetate of lead. It dissolves 
a large quantity of hydrate of lime, and gives by evaporation in vacuo a yel- 
low crystalline mass, of which M. Liebig infers the composition to be C 42 H 23 
18 +3CaO,3HO, from an analysis by Stass. Phloridzin is a febrifuge like 
salicin. 

Phloretin, C^H^O^. When a solution of phloridzin is boiled with a 
little of any acid whatever, except nitric and chromic acids, it is converted into 
grape sugar, and the present compound, which separates from the solution as a 
crystalline powder. Phloridzin thus undergoes a similar change with salicin, 
by the action of acids. 

Nitrophloretic acid, phloretic acid (Stass,) C 30 H 12 O, 5 N; an uncrystalli- 
zable matter of a puce colour, obtained by the action of nitric acid on phlo- 
ridzin. It is soluble in alkaline solutions, and precipitated again by acids. 

Phlorizein, C 42 H 2fi 26 N 2 ; a red substance soluble in ammonia, which is 
obtained by the joint" action of air and ammonia on humid phloridzin. The 
addition of 8 atoms of oxygen and 2 atoms of ammonia to the elements of 
anhydrous phloridzin, gives exactly the composition of phlorizein. This 
compound also unites with 1 atom of ammonia, when dissolved in its solution 
and evaporated in vacuo with sticks of potash, and forms a purple blue 
powder, of a coppery lustre, very soluble in cold water, of which the solu- 
tion has a magnificent blue colour (Stass, An. de Chim. lxix. 367.) 



596 GLYCERIN, 



SECTION IV. 



GLYCERIN. 



Glyceryl, C 6 H 7 =G1; a hypothetical radical admitted by Liebig to exist in 
the substance long known as glycerin, which is found combined with various 
acids in the fat oils. Glycerin is considered as a compound of glyceryl with 5 
atoms of oxygen and 1 atom of water, or the hydrated oxide of glyceryl. 

Hydrate of oxide of glyceryl, glycerin; C 6 H 7 5 -fHO. This substance 
was first observed by Scheele, and distinguished by him as the sweet principle 
of oils, its function in the constitution of oils and fats was developed by Chevreul, 
and its composition carefully determined by Pelouze.* It forms a base to the 
oleic, stearic, and margaric acids of the fat oils and tallow, and is separated 
when those acids are made to combine with an alkali or any metallic oxide, in 
the saponification of the oils. It is conveniently prepared in saponifying oil 
of olives with oxide of lead and a little water, by boiling them together ; the 
liberated glycerin dissolves in the water, while the soap of oxide of lead 
is insoluble. The glycerin is accompanied by a small quantity of oxide of 
lead in solution, which may be precipitated by sulphuretted hydrogen. Or 
when an oil is converted into a soap by boiling it with water and an excess of 
alkali, the soap comes to the surface being insoluble in the alkaline liquor. The 
latter, which contains the glycerine in solution, may be drawn off, the free alkali 
be neutralized with sulphuric acid, and the solution evaporated to a syrup, from 
which strong alcohol dissolves out the glycerin. If the product is coloured it 
may be purified by means of animal charcoal, evaporated by a water-bath, and 
afterwards in vacuo over sulphuric acid. 

Glycerin is thus obtained as a syrup, colourless or slightly yellow and un- 
crystallizable, inodorous, very distinctly sweet, of density 1.252 to 1.27, attracting 
moisture from the air, and miscible in all proportions with water and alcohol, 
but insoluble in ether. It rises in small quantity with the vapour of water, but 
cannot be distilled without partial decomposition. When heated in air glycerin 
burns with a luminous flame. It possesses an extraordinary solvent power, 
scarcely inferior to that of water itself It dissolves the deliquescent salts, and 
many other salts which are not deliquescent, as sulphates of potash, soda and 
copper, nitrates of silver and potash, the alkaline chlorides, hydrates of potash 
and soda, and the vegetable acids. Nitric acid converts it slowly into oxalic 
acid; peroxide of manganese with sulphuric acid into formic and carbonic acids. 
Its solution in water does not undergo any change by keeping, and is not fer- 
mentable by yeast. Glycerin is decomposed when boiled with a solution of 
sulphate of copper, and metallic copper precipitated. It is not precipitated by 
subacetate of lead, but is itself when hot capable of dissolving oxide of lead. 
With potash it forms a compound soluble in alcohol ; it combines also with 
barytes. 

It is acted upon by chlorine and bromine ; the latter forms, with hydrobromic 
acid, a heavy oily ethereal liquid, C T 2 H 1 ^raOj , soluble in alcohol and ether. 
With chlorine, the product is a white solid flocculent substance, C x 3 H, ,0^0, . 

* Ann. de China, et de Phys. t. 63, p. 19. 



ETHAL. 597 

Mcid sulphate of oxide of glyceryl sulpho glyceric acid; HO. C 6 H 7 5 -f-S 2 
6 . When glycerin is mixed with twice its weight of concentrated sulphuric 
acid, combination takes place with the evolution of much heat, but without 
charring. The liquid when diluted and neutralized with carbonate of lime gives 
a precipitate of sulphate of lime, which is separated by filtration, while sulpho- 
glycerate of lime remains in solution. The acid may be isolated by cautiously 
precipitating the lime by means of oxalic acid. But it cannot be preserved, for 
it is gradually decomposed and converted into hydrate of oxide of glyceryl and 
sulphuric acid ; the change takes place still more rapidly when the liquor is 
slightly heated. Even when newly prepared, this acid liquid precipitates lime 
and barytes from their salts. 

Sulphate of oxide of glyceryl and lime, CaO.C 6 H 7 5 -{-S,0 6 , (Pelouze.) It 
is deposited from its solution evaporated to the consistence «f a syrup in pris- 
matic needles or colourless plates, which are insoluble in alcohol and ether. 
The salt of lead has a composition analogous to that of lime. The solutions of 
both of these salts are decomposed by ebullition, and resolved into insoluble 
sulphates and hydrated oxide of glyceryl. 

M. Liebig makes the remark that oxide of glyceryl probably exists in na- 
ture combined with other acids besides those of the fats. Thus a benzoate of 
oxide of glyceryl would possess the same composition as picrotoxin ; mannite 
even might be an oxide of glyceryl. (Traite, I. 602.) 



SECTION V. 



ETHAL, AND THE CETYL SERIES OF COMPOUNDS. 

Spermaceti differs from the other natural fats in affording a peculiar substance, 
first observed by Chevreul, instead of glycerin, when saponified by an alkali. 
This substance was named ethal* by MM. Dumas and Peligot, who consider it 
the alcohol of a new series of compounds, of which the radical is cetyl ; or ethal 
is the hydrate of oxide of cetyl. 

Formula of cetyl C 3 2 H 3 3 =Ct. Has not been isolated. 

Hydrate of oxide of cetyl, ethal; C 32 H 33 0-f HO. To liberate ethal from 
spermaceti, the latter is digested with an equal weight of hydrate of potash dis- 
solved in 2 parts of water, at a temperature not exceeding 200° for several 
days. The soap thus formed which consists of oleate and margarate of potash 
with ethal, is then decomposed by dilute sulphuric acid, which gives a fatty 
mass, composed of the oily acids and ethal in a state of mixture and not of 
combination ; it is washed well with boiling water, and then boiled with barytes 
water in excess, which forms insoluble soaps with the oleic and margaric acids; 
and ethal is dissolved out by means of cold alcohol, which is afterwards distilled 
off. The ethal is dissolved in ether, to separate a trace of adhering barytic 
salts. 

Ethal is deposited from an alcoholic solution in crystalline plates ; it fuses 
above 1 18°, and solidifies at that temperature, forming a white crystalline mass. 
It is volatile, and may be distilled without decomposition. It is insoluble in 
water, soluble in alcohol and ether, neutral and does not combine with acids 
or alkalies. It is decomposed by nitric acid, and combines with sulphuric 
acid. 

* A word formed of the first syllables of ether and alcohol. 



598 ETHAL. 

Chloride of cetyl, C 32 H 33 ,Cl=CtCl. — An oily liquid, formed by the action 
of perchloride of phosphorus on ethal. 

Acid sulphate of oxide of cetyl; HO.CtO,S 2 6 . — This compound is formed 
when ethal is heated with strong sulphuric acid. It forms double salts when 
neutralized with bases. Sulphate of oxide of cetyl and potash, KO.CtO,S 2 6 , 
is prepared by adding an alcoholic solution of hydrate of potash to the preceding 
compound, sulphate of potash precipitates, and the salt in question remains dis- 
solved in the alcohol, from which it is deposited in white pearly scales (Dumas 
and Peligot, Annales de Chimie, &c, Ixii, 5.) 

Ethalic acid, HO -f C 3 2 H 3 x O 3 . This compound, the acetic acid of the cetyl 
series, was formed by M. Dumas, by mixing 1 part of ethal with 5 or 6 parts 
of the mixture of hydrate of potash and quicklime, and heating to 410° or 428° 
(210° or 220° ce^itig.,) for five or six hours. Hydrogen gas is evolved, and 
the ethalate of potash formed. The last is decomposed by hydrochloric acid, 
and the ethalic acid, which separates in flocks, purified by boiling it with the 
acid liquid, and repeatedly with water, converting it into ethalate of barytes, 
and treating the last with boiling alcohol, to dissolve out undecomposed ethal. 
The ethalate of barytes is then decomposed by hydrochloric acid, and the li- 
berated ethalic acid purified by solution in ether. 

Ethalic acid is solid, white, inodorous, tasteless, lighter than water. Fused 
by heat, it solidifies at 101°, and then presents itself in the form of small brilliant 
needles, in groups radiating from a centre. It is insoluble in water, but is dis- 
solved largely by alcohol and ether. When heated in a little capsule, it boils 
like ethal, and is volatilized without leaving any residue. 

All the ethalates are insoluble in water or alcohol, except those of potash, 
soda, and ammonia. The insoluble ethalates are prepared by precipitating the 
metallic salts dissolved in alcohol, by an alcoholic solution of ethalate of potash 
or soda. The ethalates of the alkalies are decomposed by a large quantity 
of water, although they dissolve in a small quantity without change. (Dumas 
and Stass, An. de Chim., &c. lxxiii, 124.) 

Cetene, C 32 H 32 . This hydrocarbon was obtained by MM. Dumas and 
Peligot, by distilling ethal repeatedly with glacial phosphoric acid, which de- 
prives the former of 2 atoms of water. It is an oily, colourless liquid, boiling 
at 527°; the density of its vapour is, by experiment, 8007; by calculation, sup- 
posing its combining measure 4 volumes, 7943. It is insoluble in water, so- 
luble in alcohol and ether. 



PECTIN. 599 



CHAPTER VII. 

OTHER INDIFFERENT SUBSTANCES. 
Class i. Ordinary Constituents of Plants. 

SECTION I. 

PECTIN. 

Formula: HO-f-C^H^O, ,. This name was applied by Braconnot to a 
principle which forms the basis of vegetable jelly.* It is extensively diffused 
in the juices of pulpy fruits and roots, especially at the time of their maturity, 
and occasions these juices to coagulate, when mixed with alcohol or boiled 
with sugar. It may be prepared from apples, for instance, by heating the 
juice with a little albumen till the latter coagulates, filtering, and precipitating 
the pectin by a considerable addition of alcohol to the liquid. By a second 
solution in water, and precipitation by alcohol, the pectin is completely puri- 
fied. When only a small quantity of alcohol is added to the watery solution, 
the juice fixes as a jelly after an interval of one or two days. 

After being washed on a filter and dried, pectin is semitransparent, and has 
a considerable resemblance to isinglass. It is insoluble in alcohol, soluble in 
water, the solution is neutral to test paper, insipid or tasteless; it is not adhe- 
sive like gum arabic. The dried pectin swells up in water, and more readily 
in cold than in hot water; with one hundred times its weight of water it forms 
a jelly, with a larger quantity only a gelatinous liquid. It resembles vegeta- 
ble mucilage in many of its properties; with nitric acid it first forms saccharic 
acid, afterwards mucic acid. It is dissolved by an excess of alkali, and con- 
verted into the following isomeric acid. 

Pectic acid. This substance is conveniently obtained by grating yellow 
carrots to a pulp, expressing the juice, washing the marc several times suc- 
cessively with distilled or rain-water, and expressing it well again. The marc 
is then diffused through six times its weight of pure water, free from earthy 
salts, and solution of pure caustic potash gradually added by small portions. 
The mixture is then heated and made to boil for about a quarter of an hour, 
and the boiling liquor filtered through a cloth. The mixture is known to 
have boiled long enough, when a small portion of it, after being filtered, is 
found to become a jelly on adding to it a drop or two of acid. 

The pectic acid may be separated by a strong acid, but as it is then difficult 
to wash, it is preferable to precipitate it by chloride of calcium, which gives 
the pectate of lime, in the form of a coagulated jelly completely insoluble in 
water. This jelly is washed on a cloth, boiled with water, to which a little 

* From ir»KTn, coagulum. 



600 ESSENTIAL OILS. 

hydrochloric acid is added, which dissolves the lime and leaves the pectic 
acid; the last is then washed with cold water. Pectic acid remains as a trans- 
parent and colourless jelly, faintly acid, very slightly soluble in cold water, 
but more soluble in boiling water. The filtered solution does not become 
solid on cooling, but it coagulates and forms a jelly when alcohol is added to 
it, or sugar, which has the property of dissolving pectic acid, and transforming 
it after some time into a jelly, a property on which is founded the preparation 
of the jelly of currants* apples, goose-berries, &c; fruits of which the juice 
mixed with sugar coagulates in the course of a few days. When evaporated 
to dryness, pectic acid resembles pectin in appearance, and has the same com- 
position. It is a bibasic acid. The pectates possess the property of forming 
a jelly when precipitated, in common with the acid. Those only containing 
an alkaline base are soluble in water, and they dissolve only in the latter when 
pure and free from acid or earthy salts. (Berzelius, Traite II. 367 and 467.) 
By boiling it with an excess of caustic alkali, pectic acid is again modified, 
and converted into another acid, which dissolves easily, is very fluid and has 
a sour taste. This second acid is also isomeric in its salts with pectin. 



SECTION II. 



VOLATILE OR ESSENTIAL OILS AND RESINS. 

These oils or essences occur in all smelling plants, and are the source of 
the fragrance of the vegetable kingdom. Some plants, such as thyme, con- 
tain a volatile oil in all their parts; in others the oil is confined to particular 
parts, such as the flower, the pollen, the leaves, the root or the bark. In 
most plants the oil is contained in little sacs or vesicles, so well closed that 
the plant may be dried without evaporation of the oil, and the latter is pre- 
served for years from the influence of the air. In other species, and particu- 
larly in flowers, the oil is constantly produced at the surface, and dissipated 
by evaporation the moment of its formation. Essential oils are generally ob- 
tained by distilling the plant with water. They are themselves less volatile 
than water, but are carried over with the steam, owing to the sensible tension 
of their vapour at 212°, and condensing in the refrigeratory are found on the 
surface of the distilled water or at the bottom of the vessel. A few oils are 
obtained by expression, such as those of the oranges and lemons, where the 
oil resides in the epidermis of the fruit. Some other oils which are not con- 
tained in vessels, such as those of violet, jasmine, &c. are obtained by mace- 
ration of the flowers in an inodorous fixed oil, and are used in this state in 
perfumery, or are afterwards obtained apart by distilling the fixed oil with 
water. 

The essences are generally liquid, but occasionally solid at the usual tem- 
perature; they have all a strong odour, more or less agreeable, which is some- 
what harsh immediately after distillation but improves with keeping, although 
in general the odour is never so agreeable as that of the fresh plant. Their 
taste is acrid and burning, or only aromatic when it is greatly weakened by 
mixing them with other substances. Some of these essences are colourless, 
most of them yellow, red or brown, others green, and a small number are 
blue. They are not unctuous to the touch like the fixed oils, but feel harsh. 
They produce an oily stain upon paper which disappears on drying. Their 
density varies from 0.759, the density of oil of coriander, to 1.096, the den- 



ESSENTIAL OILS. 601 

sity of oil of sassafras; but they are generally lighter than water* Although 
volatile at the ordinary temperature, their boiling point is usually not under 
320°. The volatile oils are nearly all decomposed in part when distilled 
alone. They burn in air with a bright but smoky flame. When exposed to 
cold they freeze, but generally separate into a solid and fluid portion, indi- 
cating that they are mixtures of two oils differing in fluidity; the concrete por- 
tion is termed the stearopten, and the liquid portion the elaopten of the oil.* 

The essences exposed to air deepen in colour and absorb oxygen. It has 
been observed that the odour of oils is closely related with this chemical 
change. Those which oxidate most rapidly have the strongest smell, and the 
characteristic odour of no oil can be perceived immediately after its distillation 
in an atmosphere of carbonic acid gas. The oil becomes in time thick, loses 
its odour, and is transformed into a resin which in the end becomes hard. A 
small quantity of carbonic acid is formed in this transformation, but no water; 
it is greatly promoted by light. An oil which has commenced to undergo 
this change consists of a portion of oil unchanged, holding a resin in solution, 
from which the former may be separated by distillation with water. The 
substance turpentine is in this condition, and gives oil of turpentine, when 
distilled, with common resin as the fixed residue. Essences should, there- 
fore, be preserved in well-stopped bottles. They are strongly acted upon and 
frequently inflamed by concentrated nitric acid. Some of them produce a 
sort of explosion when mixed with dry iodine. 

Essential oils are very slightly soluble in water, but sufficiently so to com- 
municate their odour and taste to that liquid. Water which has been distilled 
from an odoriferous plant is a saturated solution of the oil; the distilled waters 
used in medicine are so prepared. These liquors are improved by a second 
distillation, or by keeping for some time in a cool place when contained in 
opaque vessels imperfectly closed, during which some foreign matters which 
have been distilled along with the oil, disappear. The volatile oils are all 
very soluble in alcohol, and the more so the less water it contains. With 
alcohol of 0.820, oil of turpentine may be mixed in a large proportion, and 
such a liquid is sometimes burned in a lamp properly constructed for the pur- 
pose. The oils which contain oxygen, such as those of lavender and pepper- 
mint, dissolve more readily in aqueous alcohol than the pure hydrocarbons. 
Such solutions of essential oils in alcohol are lavender water, eau de Cologne, 
&c. They are rendered turbid by water, which combines with the alcohol 
and liberates the oil. Essential oils are soluble in ether. They are capable of 
dissolving at a high temperature a considerable quantity of sulphur and a small 
portion of phosphorus; and may be combined or mixed with bisulphuret ot 
carbon, chlorides of sulphur, of phosphorus, of carbon and arsenic. They 
combine with several vegetable acids, such as acetic, oxalic, succinic acids, 
the oily acids, camphoric and suberic acids. With the exception of oils of 
cloves, cinnamon and cedar wood, the volatile oils do not combine with salifi- 
able bases; they differ entirely in this respect from the fixed oils which are 
saponified by alkalies. After being brayed with sugar the volatile oils dissolve 
better in water. Volatile oils dissolve all the fat oils, resins, and animal fats. 

Many volatile oils contain no oxygen, and in all of these, with one or two 
exceptions, the carbon and hydrogen are C 5 H 4 , or some multiple of these num- 
bers ; but the larger proportion are oxides. Several of the latter part withtheir 
whole oxygen, with a proportional quantity of hydrogen, as water, under the 
action of anhydrous phosphoric acid, and are converted into pure oily hydro- 
carbons. 

* These terms were first applied to the solid and fluid portions of fixed oils; they are 
derived from fTMf suet and sa*/ov oil. 
51 



602 ESSENTIAL OILS. 



A. ESSENTIAL OILS CONTAINING NO OXYGEN. 



OIL OF TURPENTINE. 

Formula: C 20 H 16 . It is derived from several kinds of turpentine, a semi- 
fluid resin exuding from the different species of the pine. The turpentine is 
distilled with water, the oil comes over, and a resin remains behind. The oil 
met with in commerce generally contains some resin, produced by the oxidation 
of the oil, from which it should be purified by rectification, that is, a second dis- 
tillation from water. The pure oil is a colourless, thin liquid, having a peculiar 
odour, of which the density is 0.872 at 50°, and boiling point 314°.2 (156°.8 
centig.) The specific heat of this liquid is 0.462, according to Despretz, that 
of water being 1.000. The density of its vapour is 5010 by experiment, 4763 
by calculation. It abandons only half the heat when condensed from the state 
of vapour at its boiling point, that vapour of water does at 212° ; but a portion 
of that heat is heat of temperature, for the latent heat of vapour of oil of turpen- 
tine is to that of vapour of water only as 0.313 to 1.000. When cooled to 
— 16°.6, oil of turpentine deposites its stearoptenin white crystals, which are 
heavier than water, and fuse at 19°. 4 ( — 7° centig.) 

Oil of turpentine is certainly a mixture of two or more isomeric oils ; this ap- 
pears in its forming two compounds with hydrochloric acid, one of which has 
long been known as artificial camphor. To prepare this compound, well dried 
hydrochloric acid gas is made to pass slowly into the essence surrounded by 
ice. Without this precaution, it becomes hot, and the hydrochloric acid is not 
so completely absorbed. It is left to itself for twenty-four hours, after which a 
quantity of white crystalline substance is found deposited in a brown fuming 
mother-liquor. The composition of the solid hydrochlorate is represented by 
C^Hj 6 -f-HCI. The name camphene being applied to the essence by Dumas,* 
this is the hydro chlorate of camphene. When pure it is a snow-white substance, 
of a peculiar odour, suggesting that of common camphor, but very different in 
other respects ; fusible above 212°, and volatile; alcohol of 0.806 dissolves at 
57° one third of its weight of it. It is decomposed completely when distilled 
rapidly by means of an oil-bath, with two or three times its weight of quicklime, 
chloride of calcium being formed, and a colourless oil of the same composition 
and density as oil of turpentine, which can be united again with hydrochloric 
acid, and gives an entirely solid product. This oil, however is not identical with 
the essence, differing from it in its optical properties, and is distinguished as 
eamphilene (Deville.) The liquid hydrochlorate is of density 1.017, and its com- 
position is also expressed by C 2 4 H 16 -J-HC1. (Soubeiran, Capitane.) 

It is difficult to decompose the hydrochlorate of turpentine completely by 
an alkali; a portion of it distils over and contaminates the oil thus obtained. 
M. Deville adds gradually to essence of turpentine kept cold, a small quantity, 
about l-20th of oil of vitriol, so that the whole becomes deep red and viscid 
after strong agitation, allows it to deposite for twenty-four hours, and decants 
the thick liquid from a black deposite. This red liquid, when heated, emits 
some bubbles of sulphurous acid, becomes colourless, and is transformed into 
a mixture of two oils, which he names terebene (from terebenthine,) and colo- 
phene. The former distils over first. Terebene has the same composition 
and density as camphene, but differs from the latter in its rotatory power on 

* The essence of turpentine may be allowed, as the base of artificial camphor, to retain 
this name. 



OIL OF TURPENTINE. 603 

polarized light being equal to nothing. By treating terebene by hydrochlo- 
ric acid, Deville obtained a new liquid, subhydrochlorate of terebene, of den- 
sity 0.902 at 59°, with a good deal of the odour of terebene itself; its compo- 
sition 2C 20 H 16 +HC1. A corresponding hydrobromate of terebene was a 
colourless liquid, of density 1.021 at 75°. 2 (24° centig.;) its composition 
2C 20 H 16 -f-HBr. The solid hydrobromate of camp hene, formed by the ac- 
tion of hydrobromic acid on the essence is C 20 H 16 -fHBr. It preserves, in 
common with the solid hydrochlorate, the negative rotatory power of the es- 
sence. The liquid hydrochlorate, prepared from the essence, loses that pro- 
perty, and is, therefore, supposed not to contain camphene but terebene, and 
named hydrochlorate of terebene. When hydrochlorate of terebene is dis- 
tilled with an alkali, it gives an isomeric oil, terebiiene, having the same re- 
lation to terebene that camphilene has to camphene. Two corresponding 
hydriodates of terebene have been formed. 

A very regularly crystallized substance has often been found in old oil of 
turpentine, or in oil of turpentine left long in contact with dilute nitric acid, 
which appears to be formed by the assimilation of the elements of water. 
Its composition is C 90 H 22 O 6 , or represented as a hydrate of oil of turpen- 
tine C 20 H lfi -f 6HO. " (Dumas and Peligot.) It is fusible about 302° (150° 
centig.,) and sublimes. Soluble in 200parts of cold, and in 22 parts of boil- 
ing water, from which it crystallizes o^cooling. 

By treating terebene by chlorine, M. Deville formed two liquid chlorinated 
compounds, which he names chloroterebene, C 20 H 12 C1 4 and mono chlo rot ere- 
bene, C 20 H 14 CJ 2 . He also formed bromoterebene, C 20 H 12 Br 4 . Terebene 
does not form a hydrate like the essence. The essence treated with chlorine 
gives a chlorinated compound, which M. Deville names chforocamphene, of 
the same composition as chloroterebene, but differing in density and other 
properties. 

Colophene is an additional product besides terebene, of the action of concen- 
trated sulphuric acid upon the essence. It distils over after the terebene, on 
urging the heat so as to bring the viscid mass in the retort to a state of strong 
ebullition, as a viscid oil, of a clear yellow colour, which re-distilled several 
times alone, and once (if contaminated with sulphur) from the alloy of potas- 
sium and antimony, constitutes colophene. Colophene is colourless by trans- 
mitted light, but possesses a kind of dichroism and may be seen of a deep indigo 
blue colour, a property which can be recognised in all its compounds. Its den- 
sity is 0.940 at 48°, and 0.9394 at 77°. It is isomeric with the essence of turpen- 
tine. Its boiling point is about 590 or 600°; the density of its vapour could 
not easily be taken with exactness, but was certainly not less than twice that 
of oil of turpentine. Assuming the density as double, the atom of colophene 
will be C 40 H 32 , its combining measure 4 volumes. This oil is also one of 
the products of the rapid distillation of colophony or the resin of turpentine, 
and was named colophene on that account. 

Colophene absorbs hydrychloric acid, but the hydrochlorate is a feeble com- 
bination, and is deprived of its acid by chalk. By distilling the impure hy- 
drochlorate from baiytes, M. Deville obtained an isomeric oil, which he con- 
siders the colophilene of colophene. It did not appear, however, to possess 
the dichroism of the latter body. Colophene also absorbs chlorine with 
avidity, without any disengagement of hydrochloric acid, and is converted 
into a resin, soluble in alcohol and crystallizable, having very much the ap- 
pearance of colophony, and which is named chlorocolophene, C 40 H. {2 C1 4 . 
It is in fact colophony in which 4 atoms of oxygen are replaced by 4 atoms 
of chlorine. Fused by heat, and exposed again to chlorine chlorocolophene 
absorbs that gas, and emits a large quantity of hydrochloric acid, giving a new 



604 ESSENTIAL OILS. 

product, of a transparent yellow colour, which may be represented by C 40 
H„C1 4 . 

It thus appears that four isomeric oils exist related to the essence of turpen- 
tine, of which the common formula is C 2 H 1 6 , namely camphene, terebene with 
camphilene and terebilene, the two latter being obtained by similar processes 
from the two former; also another pair, of which the atomic weight is double 
and the formula C 40 H 32 , namely colophene and colophilene; and that each of 
these bodies gives rise to a particular series of compounds by uniting with 
hydrochloric acid, chlorine, &c. (Deville, An, de Chim. Ixxv, 37.) 



COLOPHONY, OR RESIN OF TURPENTINE. 

Common turpentine affords when distilled with water from 5 to 25 per cent 
of essence, what remains being common resin, named colophony, or colopho- 
nium, of which the composition generally received is C 40 H 32 O 4 (Rose;) that 
is, 2 equivalents of the essence combined with 4 equivalents of oxygen. M. 
Liebig is disposed, from more recent analyses, to represent the resin by G 40 
H 30 O 4 , and then in its formation, the essence C 40 H 32 loses 2 atoms of 
hydrogen, which are replaced by 4 atoms of oxygen. The resin is not, 
however, a homogeneous product,H)ut was divided by M. Unverdorben 
into two different resins, which he named sylvic and pinic acids. The 
properties of the mixture of these resins or colophony are familiar; it is a 
yellowish brown, translucent, brittle solid, fusible, readily soluble in alcohol, 
ether, the fixed and volatile oils ; soluble in alkaline leys, with which it combines 
as an acid, and forms soluble salts, which are detergent, and enter largely into 
the composition of all brown soaps. The two resins are separated from each 
other by means of cold alcohol, of 72 per cent. (sp. gr. 0.867,) which dissolves 
pinic acid, or alpha-resin as it is also called, and leaves behind sylvic acid, or 
beta-resin. 

iSlpha-resin (pinic acid,) is precipitated from the alcoholic solution by water; 
it is not crystal liz able ; after being fused, it has quite the appearance of colo- 
phony ; it is insoluble in water, but dissolves easily in alcohol, ether, and oil of 
turpentine ; these solutions have an acid re-action. The pinates of potash, soda 
and ammonia dissolve in water, but are precipitated by an excess of alkali or 
the addition of any alkaline salt. The pinates of other bases are insoluble in 
water, and may be precipitated from alcoholic solutions of the alkaline pinates by 
double decomposition, employing an alcoholic solution of the other salt ; they 
are most frequently insoluble in alcohol, but many dissolve in ether. The com- 
position of pinic acid was found by Rose to be C 40 H 32 O 4 , or the same as that 
of colophony (C 40 H 30 O 4 , according to Liebig.) Sylvic acid has likewise the 
same composition. 

By distilling or heating pinic acid, a new resin is formed, colopholic acid, of 
the same composition but possessing a stronger affinity for bases. 

Beta-resin (sylvic acid.) The insoluble residue treated with boiling alcohol, 
dissolves entirely ; it is filtered hot, and crystallizes on cooling. It is purified 
by a second crystallization, particularly from alcohol containing a little sulphuric 
acid. It is transparent and colourless, crystallizes in rhomboidal prisms, termi- 
nated by four facets, which are generally very thin, and so large as to resemble 
tables. It fuses below 212°, is insoluble in water, but dissolves easily in alcohol, 
ether, the fixed and volatile oils. Alcohol of 72 per cent, takes up, when boiling, 
one-third of its weight, but abandons nearly the whole on cooling in a crystalline 
form. It is dissolved by concentrated sulphuric acid, and precipitated again by 
water from, that solution, but in the condition, according to Unverdorben, of 



RESIN OF TURPENTINE. 605 

pinic acid. The sylvates of potash, soda and ammonia are soluble in water,- 
the sylvates of other bases are insoluble in water, but frequently dissolve in 
ether and even alcohol. The sylvate of magnesia, in particular, is soluble in 
alcohol. The addition of ammonia, even in excess, to the solution of sylvic acid 
in alcohol does not throw down a precipitate, and the acid precipitated by water 
dissolves readily in ammonia; so also does the resin in caustic potash, but an 
excess of the latter throws down a subsylvate of potash, a compound very 
slightly soluble in an excess of base. The composition of sylvic acid is C 4 H 3 
4 , or half these numbers, according to Tromsdorff. 

These two resins form the large proportion of colophony, but a third resin 
has been observed in it, which is indifferent, soluble in cold alcohol, but not 
precipitated by the acetate of copper. 

The white resin, galipot, derived from the pinus maritima, consists almost 
entirely of a colourless, crystallizable resin named pimaric acid, C 40 H 30 O 4 , of 
the same composition as the preceding resins, but differing from them in pro- 
perties. . When the crystallized resin is dissolved in alcohol, it soon separates 
as an amorphous powder, which is much less soluble, without alteration in com- 
position. When distilled in vacuo, pimaric acid is converted into another resin, 
pyromaric acid. Boiled for a long time with nitric acid, pimaric acid gives rise 
to a new acid, containing nitrogen, azomaric acid, C 40 H 18 O 12 N+4HO, of 
which the capacity of saturation is double that of pimaric acid. (Laurent, An. 
de Chim. lxxii, 383.) 

By the dry distillation of colophony, M. Fremy obtained a heavy light- 
coloured oil, almost destitute of taste and smell, boiling above 482°, which he 
named resinein. Its composition is expressed by C 2 H X 5 ; and it appears to 
be formed by the abstraction of an atom of water from half an equivalent of 
colophony. By distilling purified resin with eight times its weight of slacked 
lime, the same chemist procured two liquid products, resinone C 10 H 9 O, soluble 
in alcohol, and boiling at 1 72° . 5 ; and resineone C 2 3 H x 8 O, less soluble in alcohol, 
and boiling at 298°.5 (Liebig, Annalen, xv, 282.) 

By distilling resin at a higher temperature, MM. Pelletier and Walter obtained 
a liquid, retinaphtha C 7 H.; which gives with chlorine a compound C 14 H 6 C1 2 . 
At the same time with retinaphtha, a less volatile liquid, retinyle, C 9 H 6 , is 
formed. The less volatile product of the distillation of resin affords a liquid 
retinote, C 8 H 4 , with a solid compound relist erene or metanaphthaline, which is 
isomeric with naphthaline. (Ann. de Chim. &c., lxvii, 269.) 

Common resin is converted into shoemaker's resin, or Burgundy pitch, by 
heating it repeatedly with water, and going to dryness. 

Oil of lemons, C l H S . This essence is extracted from the rind of the lemon 
(Citrus medica,) usually by expression. The crude oil is pale yellow, but 
when rectified it is colourless, has a strong smell of lemons, density 0.847, and 
boiling point 343°.4 (173° centig.) It has absolutely the same composition in 
1 00 parts as essence of turpentine, but only half the atomic weight. It forms,, 
with hydrochloric acid both a solid and liquid compound, according to Blanchet 
and Sell. The composition of both is expressed by C 10 H 8 HC1. The camphor 
and also the liquid hydrochlorate of lemon oil are decomposed by means of 
alkalies, and furnish two oils, wiiich possess the same composition as the essence 
employed. Oil of oranges, from orange-peel (Citrus aurantium) differs only 
in smell from oil of lemons. Oil of neroli, or of orange-flower is quite different, 
and is in great part soluble in water. It appears to contain a stearopten, but 
its composition is not exactly known. 

Oil of junipers. — Obtained by the distillation of crushed juniper-berries with 
water. It is colourless, and possesses the taste and odour of juniper ; is com- 
posed of two oils of different volatility, both of them containing carbon and 

51* 



606 ESSENTIAL OILS. 

hydrogen in the same relation as all the oils of this class, namely C 5 H 4 . By 
adding a little of this oil to brandy, gin or Hollands are formed. 

Savin oil. — Derived from the berries of Juniperus sabina, colourless, also 
represented by some multiple of C 5 H 4 . Both of these oils are used as diuretics. 

Oil of copaiba, C 10 H 8 . The balsam of copahu or copaiva is extracted in 
Brazils and the Antilles from several plants, of the genus copaifera. It is ob- 
tained by incision, in the same way as common turpentine, with which it has 
a great analogy; and is a clear yellow, transparent, thick liquid, consisting of a 
resin and volatile oil. 

The oil is colourless, thin, of an aromatic but disagreeable odour, of density 
0.878, and boiling point 473°. Absolute alcohol dissolves two-fifths of its weight 
of this oil, but twenty-five parts of the spirits of wine of commerce, are required 
to dissolve one part. It forms a crystallizable compound with hydrochloric 
acid ; it is isomeric with oil of lemons, and has the same mode of condensation. 
(Blanchet.) 

Copahuvic acid, C 40 H 32 O 4 . This name is applied to the resin of copaiva, 
which possesses, according to Rose, the same composition as colophony. To 
obtain it crystallized, M. Schweizer dissolves 9 parts of the balsam in 2 parts 
of ammonia, and leaves the mixture in a cool place. The crystals which form 
being taken out, washed with ether, and re-dissolved in alcohol, furnish the pure 
resin by spontaneous evaporation ; the salt of copahuvic acid and ammonia loses 
its ammonia during the evaporation. The copahuvates of potash and soda are 
soluble in water, that of ammonia soluble in ether and alcohol, but not in water. 
The salt of silver is crystallizable. 

Oil of pepper, from Piper nigrum, has the same composition as oil of copaiva* 
and is similar in properties. 

Oil of cubebs, from Piper cubeba, is supposed by Soubeiran and Capitaine to 
be C 15 H 12 . its compound with hydrochloric acid being C Xb M x 3 C1. The 
former is still a multiple of C 5 H 4 . 

Oil of storax, from the balsam storax liquida, by distillation, has, according 
to Marchand, its carbon and hydrogen as C 2 H, or in the same relation as ben- 
zole, and therefore differs in composition from all other known essential oils. 
It is converted by nitric acid into a resinous body, which yields a particular 
crystallizable oil, by distillation, the nilrostyrole of Simon. 

Oil of elemi, obtained by distilling the resin, is a transparent colourless liquid, 
of an agreeable smell, its density is 0.852 at 75°.2 (24° centig. ;) it absorbs 
hydrochloric acid, but does not seem to form a solid camphor. It consists of 
carbon and hydrogen in the proportion of C 4 H 5 . (Stenhouse.) 

Laurel-turpentine oil, imported of late from Demarara under the name of 
laurel oil ; its density is 0.8645 at 60°, it begins to boil at 301°, but its boiling 
point rises to 325°. Its smell slightly resembles that of oil of turpentine, but is 
much more agreeable and approaches that of oil of lemons. It contains no 
oxygen, and consists of two or more isomeric oils of theC 5 H 4 type. This oil 
is an excellent solvent of caoutchouc, and is employed as an external application 
in rheumatism. (Stenhouse.) 



B. ESSENTIAL OILS CONTAINING OXYGEN. 

Oil of bergamotte is obtained from the ripe fruit of the Citrus bergamotfa, or 
Citrus limetla (the lime.) It is yellowish, but when rectified, colourless, has an 
agreeable odour, and is much used as a perfume. Its density is 0.862 ; it com- 
bines with hydrochloric acid. It was found by Ohme to contain 7.098 per cent, 
of oxygen, and considered as a hydrate of lemon oil, 3C 10 H 8 -f-2HO. But 
MM* Soubeiran and Capitaine find it to be a mixture of 2 or more oils, which 



OIL OF ANISE. 607 

differ in volatility, but could not be completely separated, with the proportion 
of oxygen varying from 3.37 to 16.14 per cent. By the action of anhydrous 
phosphoric acid upon this essence, an oil is obtained which has the same com- 
position as oil of lemons, or is of the C 5 H 4 type. By the action of phosphoric 
acid on the impure oil a peculiar acid was also produced (named phospho-ber- 
gamic acid,) which forms soluble salts with lime and oxide of lead. 

Oil of cloves, from the undeveloped flower-buds of the Caryophyllus aroma- 
ticus. It is colourless or yellowish, becoming brown in air, of a strong odour 
and burning taste ; its density is 1.061. Clove oil consists of two different oils, 
one light, of the C 5 H 4 type, the other heavy, of density 1.079, and boiling point 
469°. 4 (243°. centig.) which forms crystalline compounds with bases, and is 
named caryophyllic (eugenic) acid. The two oils are separated by distillation of 
the crude oil with a solution of potash, by which the heavy or proper clove oil is 
retained in combination, and may afterwards be liberated by means of sulphuric 
acid. Alcohol also extracts from cloves a solid substance, caryophylline, of 
which the formula, according to both Dumas and Ettling, is C 20 H 16 O 2 . The 
distilled water of cloves deposits another substance in yellowish pearly scales, 
which has been named eugenine by Bonastre. 

Oil of anise, from Pimpinella anisum, is yellowish or colourless, of density 
0.9857. It contains so much stearopten that it is solid at the usual temperature. 

The stearopten obtained by pressure of the oil cooled to 32°, crystallizes in 
colourless plates, fuses at about 64°, and boils at 431°. 6. Its composition, according 
to the latest determination of M. Cahours, is C 20 H 12 O 2 . With chlorine it 
appears to form two semifluid compounds of a viscid consistence, C 2 H 9 C1 3 2 , 
and C 20 H 7 iCl 4 iO 2 . With bromine the action is more definite, and a crystal- 
line compound is formed, bromanisal, C 20 H 9 Br 3 O 2 . If l£ parts of sulphuric 
acid are digested with 1 part of the concrete essence, the latter is entirely con- 
verted into a substance of a resinous nature, which when purified from sul- 
phuric acid by distillation, is termed anisoi'ne, by Cahours. It is a perfectly 
white inodorous substance, fusible at a temperature above 2 12-, of which the 
formula is C 20 H 12 O 2 , or it is isomeric with the original concrete essence. By 
the action of dilute nitric acid on the essence of anise, anisic acid, HO+C 16 H 6 
5 , is formed, which crystallizes in fine needles and is volatile without decom- 
position ; it belongs to the class of benzoic and cinnamic acids. When distilled 
with an excess of barytes, hydrated anisic acid loses 2 atoms of carbonic acid and 
yields anisole C 14 H 7 2 , a colourless highly mobile liquid, boiling above 302° 
(150° centig.,) of an agreeable aromatic odour, insoluble in water, soluble in.alco- 
hol. Anisole gives crystallizable and volatile compounds with chlorine and bro- 
mine ; it is evidently allied to benzole. Boiled with stronger nitric acid the con- 
crete essence of anise, gives nitranisic acid, HO-f-C 16 H.N0 9 . Nilraniside is 
a yellow resinous substance, produced by the action of fuming nitric acid upon 
the concrete essence ; its probable formula isC 20 H 10 N 2 O 10 . (Cahours, Ann. 
de Chim., &c., 3 ser. ii, 274.) 

The concrete essence of fennel and badian are found by Cahours to be abso- 
lutely identical with that of anise. The concrete essence of anise is not affected 
by alkalies, in which respect it differs from camphor, the solid essence of cedar, 
oil of mint and certain other essences. 

Oil of bitter fennel consists principally of two oils, one possessing the compo- 
sition of the concrete essence of anise ; and the other and more volatile oil 
which is much more difficult to purify, appearing to correspond in composition 
with essence of lemons and turpentine, but perhaps with a different state of 
condensation. The more volatile portion, when exposed to a slow stream of 
deutoxide of nitrogen, becomes thick and turbid, and alcohol then throws down 
from it a white silky matter, of which the composition is C 1S H 1S N 2 4 > 
(Cahours.) 



608 ESSENTIAL OILS. 

Oil of hyssop from the Hyssopus officinalis, begins to boil at 288° but its 
boiling point rises to 325°. It is a mixture of several oils, one of which proba- 
bly contains no oxygen, as by repeated rectification of a portion of the oil con- 
taining 9 per cent of oxygen with fused potash, the quantity of oxygen was re- 
duced to 1 1 per cent, the greater part of the oxygenated oil being converted into 
a brownish resin. (Stenhouse.) 

Cajeput oil, C 10 H 9 O, is obtained from the leaves of the Melaleuca leucaden- 
dron of the Moluccas. In the crude state it is green, but becomes colourless by 
rectification. Its density is 0.897. 

Oil of caraways, extracted from the seeds of the Carum carui, contains two 
different oils, one of which is probably a hydrocarbon (Voelkel.) These are 
different from the oils of the Cuminum cymimum, although the two plants be- 
long to the same family. 

Oil of cummin is extracted from the seeds of the Cuminum cymimum, The 
Roman oil was found by M. M. Gerhardt and Cahours* to consist of two oils. 
One of these oils they have distinguished as cymene ; it is a hydrocarbon 
C 2 H 1 4 , and boils at 329°. The other contains oxygen, and appears to be the 
hydruret of a compound radical like benzoyl, which may be named cumyl. 
Cymene is separated by dropping the essence into hydrate of potash in a state 
of fusion, the hydrocarbon distils over, and the hydruret of cumyl is retained by 
the alkali as cuminic acid. The known compounds of cumyl are as follows: 



Hydruret of cumyl, or cuminol . C 20 H 1 ,0 2 -f H 

Cuminic acid C^H^Ocj-fO 

Chloride of cumyl or chloro-cuminol C^H^C^-f CI 
Bromide of cumyl or bromo-cuminol C 30 H 1 ,0 2 +Br 
Hydrated cuminic acid . . . C 2& Hj j0 2 +0+HO 

Hydruret of cumyl or cuminol is a colourless or yellowish liquid of a strong 
odour, easily altered by the contact of oxygen when heated. Its boiling point 
is 428° ; density of its vapour by experiment 5240, by calculation 5094, its com- 
bining measure being supposed four volumes. Cuminol is capable of uniting 
with hydrate of potash at the ordinary temperature without the evolution of 
hydrogen. It is oxidated and converted into cuminic acid by direct oxi- 
dation, or when treated with caustic alkali in which case hydrogen is evolved, 
or by the action of sulphuric acid and chromate of potash. This acid, which 
corresponds with benzoic acid, is colourless, crystallizes in prismatic needles, 
has an acid burning taste, is scarcely soluble in water, dissolves easily in alcohol, 
and may be sublimed. When hydrated cuminic acid is distilled with 4 parts 
of caustic barytes, it yields an aromatic colourless liquid, C 1S H 12 , to which 
the name cumene has been applied ; it boils at 291°.2 (144° centig.) Cumene 
is analogous to benzin or. benzole ; it forms with fuming sulphuric acid sulpho- 
cumenic acid, corresponding with sulphobenzic acid, of which the barytic salt 
is crystallizable. With nitric acid it forms nitrocumide, analogous to nitro- 
benzide. 

Cymene has been found to correspond perfectly in density, boiling point, 
and density of vapour with camphogen from camphor, and is believed to 
be identical with it. It also appears to be isomeric with retinylene from the 
distillation of resin. It forms a sulphocymenic acid. 

Lavender oil, C 15 H 14 2 ( = 3C 5 H 4 -f 2HO.) This familiar oilis thin, 
colourless, of density 0.877. 

* Recherches chiraiques sur les huiles essentielles. An. de Chim. 3me S6rie, t. i. p. 60. 



OIL OF PEPPERMINT. 609 

Oil of peppermint from Mentha piperita is pale yellow, and lighter than 
water. It contains a variable proportion of stearopten, so much as sometimes 
to form a solid prismatic crystalline mass. The composition of the elaopten 
is C 21 H 20 O 2 ; of the stearopten C 20 H 20 O 2 . Phosphoric acid withdraws 
two atoms of water from the last, and eliminates a liquid hydrocarbon, which 
M. Walter has named menthene, C 20 H 18 . Distilled with perchloride of 
phosphorus, the stearopten also gives chloroment Irene, C 2o H 1T Cl. Chlorine 
is absorbed by the stearopten, and two different chlorinated compounds 
formed. By the action of nitric acid a liquid acid compound is produced, 
C ln H 9 3 . (P. Walter, An. de Chim. lxxii. 83.) 

Oil of cedar (solid,) C 32 H 26 2 , or C 32 H 24 -f2HO. The crude essence as 
obtained from the cedar-wood of Virginia is a soft white crystalline mass, 
which after being deprived of water by heat becomes solid at 80°. 6 (27° cen- 
tig.) Distilled by a sandpot heat, it comes over between 527 and 572° (275 
and 300° centig.,) and separates into a crystalline substance and liquid por- 
tion. The solid essence, purified by pressure and crystallization from alco- 
hol is remarkable for its beauty and lustre, its odour is aromatic and peculiar, 
suggesting that of a cedar-wood pencil. It fuses at 165°. 2 (74° centig.,) and 
boils at 539°. 4 (282°. centig.;) it is dissolved very slightly by water, largely 
by alcohol, from which it precipitates on cooling in silky crystalline needles. 
The density of its vapour is by experiment 8400; by calculation 8100, allow- 
ing its combining measure to be 4 volumes. 

When the concrete essence is distilled with anhydrous phosphoric acid, the 
latter being added in a gradual manner to prevent great elevation of tempera- 
ture, a liquid is obtained, cedrene C 32 H 26 , which appears to be the hydrocar- 
bon of the essence. Its odour is aromatic and quite peculiar, its density 
0.984, its boiling point 478°. 4 (24S° centig.;) the density of its vapour 7900 
by experiment, and 7500' by calculation, supposing its combining measure to 
be 4 volumes. Sulphuric acid and perchloride of phosphorus act upon ce- 
drene as upon menthene. The liquid essence of cedar, obtained from the 
crude essence by expression, has the same density and composition as cedrene. 
(P. Walter, An. de Chim. 3 ser. i, 498.) 

Oil of roses, otto or attar of roses, is colourless, of a most intense rose 
odour, lighter than water. Its stearopten, which is inodorous, separates at 
the usual temperature in large plates; it fuses at 95°, is very slightly soluble in 
alcohol, and contains no oxygen, but is a polymeric variety of CH. 

Oil of Mentha viridis is, according to the analysis of Dr. Kane, C 35 H 2s O. 

0/7 of valerian, extracted from the Valeriana off},': inalis, consists of a hy- 
drocarbon and oxidated oil, the last giving, when treated with potash in fusion, 
valerianic acid, the same acid as is extracted from the root of valerian, and 
obtained artificially by the action of potash upon the oil of potatoes. 

Oil of chamomile is extracted from the flowers of Matricaria chamomilla; 
its colour is deep blue. It contains a hydrocarbon and an oxidated oil, the 
last of which treated with potash in fusion gives valerianic acid. (Gerhardt 
and Cahours.) The Anthemis nobilis, Arnica montana and Archillea mil- 
lefolium, yield also blue coloured oils. 

Oil of rue, C 28 H 28 3 .: obtained by distilling fresh plants of the Buta 
graveolens; is yellowish green, of density 0.837 at 64°. 4 (18° centig.;) den- 
sity of vapour by experiment 7892; by calculation 7690, the combining 
measure being 4 volumes. This oil is soluble in sulphuric acid, and is pre- 
cipitated by water; hydrochloric acid has no action upon it. (Dr, H. Will in 
Liebig's Annalen, xxxv. 235.) 



610 CAMPHOR. 



CAMPHOR. 



Formula : C 2 H 1 6 2 or C 2 „!!, 4 -f 2HO. This essence is brought to Europe 
chiefly from Japan ; it is obtained by distilling the wood of the Laurus cam- 
phora along with water, and is refined by a second sublimation. It is in white 
translucent crystalline masses, somewhat tough, but easily pulverized when 
moistened with alcohol ; possessing a peculiar taste and smell, and may be ob- 
tained in brilliant crystals of a high refracting power, either by sublimation or 
from solution in alcohol. It floats upon the surface of water, its density being 
from 0.9857 to 0.997 ; fuses at 347°. and boils at 399°.2 (204° centig.;) the 
density of its vapour is 5317. It evaporates at the usual temperature, a pro- 
perty that contributes to produce the lively movements which small pieces of 
camphor exhibit upon the surface of pure water. Like all the essential and fat 
oils, it also possesses a remarkable tendency to diffuse a thin film of its sub- 
stance over the surface of water, the result of a kind of capillary attraction, in 
consequence of which a little column of camphor rising out of water is in the 
course of a short time cut across at the surface of the liquid. The detaching of 
the substance of the camphor by this force must occasion a recoil, which ap- 
pears to be the principal cause of the movements of a floating mass. All move- 
ment ceases when a drop of any oil is allowed to fall upon and diffuse over the 
surface of the water. Camphor is easily kindled, and burns with a white flame. 
It is but slightly soluble in water, one part of camphor requiring about 1000 
parts of water to dissolve it ; but the solution has the taste and odour of cam- 
phor. It is largely dissolved by alcohol, ether and oils. The solution in proof 
spirit, known as camphorated spirit, is precipitated by water. Camphor forms 
liquid compounds with nitric acid, acetic acid and hydrochloric acid. When 
distilled with anhydrous phosphoric acid it loses 2HO, and yields a pure hydro- 
carbon, C 20 H 14 , to which M. Dumas applied the name camphogen. 

Camphogen, after being distijled repeatedly from phosphoric acid, is a colour- 
less liquid, of density 0.861 at 57°.2, and boiling at 347°. The density of its 
vapour is by experiment 4780 ; by calculation 4697, allowing its combining 
measure to contain 4 volumes (Delalande.) Camphogen exists in some essen- 
tial oils, which are mixtu res of a liquid hydrocarbon and an oxidated oil, as the 
essence of cummin. Camphogen in its chemical relations resembles benzin or 
benzole and napthtaline. 

Hyposul 'pho-camphic acid, HO-f-C 1 H 1 3 ,S 2 5 ; is formed when camphogen 
is heated on a water-bath with a slight excess of fuming sulphuric acid ; the 
camphogen disappears without any evolution of sulphurous acid, and an acid 
is produced analogous to hyposulphobenzic acid, which forms a soluble salt with 
lead. Hypondpho-camphate of lead crystallizes in pearly plates, which contain 
4 atoms of water of crystallization, PbO-f C^B^ 3 ,S„0 5 -f 4HO ; but are made 
anhydrous by a temperature of 248°. The salt of barytes is similar in consti- 
tution. This salt and the salt of lime are remarkable for their taste, of which 
the first impression is very disagreeably bitter, but changes in a minute or two 
into a sweet and sugary taste analogous to that of liquorice. 

Camphogen also forms a white crystallizable compound when acted upon by 
fuming nitric acid. (Delalande, Ann. de Chim. 3 ser. i, 368.) 

Camphoric acid, 3130 + 3^ H 7 O 3 . This acid, which is tribasic, is produced 
by long digestion or repeated distillation of camphor with nitric acid; and is di- 
vested of adhering camphor by uniting it with potash, and decomposing the salt 
by nitric acid. It forms prismatic crystals, which are inodorous, of a very sour 
taste ; fuses at 145°.4 (63° centig.,) and emits then a pungent vapour. It sub- 



ESSNTIAL OILS CONTAINING SULPHUR. 611 

limes partially as the anhydrous acid. It is indifferently soluble in water, more 
readily dissolved by alcohol. 

Camphoric acid forms a neutral and acid salt with ammonia; the former 
contains 3 atoms of oxide of ammonium, and the latter 2 atoms of the same with 
1 atom of water as base. 

Acid camphor ate of oxide of ethyl is formed when camphoric acid, alcohol 
and sulphuric acid are heated together ; and is separated by the addition of 
water. It appears to contain a bibasic camphoric acid, of which the formula is 
C 20 H 14 O 6 united , with 1 atom of oxide of ethyl and 1 atom of water. The 
atom of water can be replaced by fixed bases, and a class of neutral salts formed. 
By boiling the acid camphorate of oxide of ethyl with water, it is resolved into 
tribasic camphoric acid, and neutral camphorate of oxide of ethyl, 2EO+C 20 
H I4 6 . (Malaguti) 

The matter considered as anhydrous camphoric acid, C 10 H 7 O 3 , is ob- 
tained pure by crystallizing in alcohol the product of the distillation of cam- 
phoric acid. It forms long flat colourless prisms, which are tasteless and in- 
soluble in water. By continued boiling in water this substance is dissolved, 
and then appears as the hydrated tribasic acid. (Laurent.) 

Liquid camphor, C 20 H 16 O; the elaopten of the oil of camphor of commerce. 
With the same proportions of carbon and hydrogen as solid camphor, it con- 
tains only half as much oxygen. The density of the pure oil is 0.91, its 
boiling point above 212°. 

Campholic acid, HO + C 20 H 17 O v The vapour, of camphor is entirely 
absorbed by a dry mixture of hydrate of potash and lime, between 300 and 
400° centig., without the disengagement of any gas, and campholate of potash 
formed. This acid has the consistence of camphor, is insoluble in water, and 
easily saturates bases; it is camphor plus HO. (Delalande, Ann. de Chim. 
etc. 3 ser. i. 120.) Campholic acid, distilled with anhydrous phosphoric acid 
yields a hydrocarbon, C 18 H l6 ,=4 volumes of vapour. (Delalande.) 

Camphrone, C 30 H 2 ,0; was obtained by M. Fremy, by dropping fragments 
of camphor into a porcelain tube containing quicklime heated to redness. It 
is a light oil, boiling at 167°, soluble in alcohol and ether but insoluble in 
water. 



C. ESSENTIAL OILS CONTAINING SULPHUR. 

Volatile oil of mustard, C 8 H 5 NS 2 . Both black and white mustard seeds 
yield a fat oil by expression. The black seed, when distilled with water, 
gives a remarkable volatile oil, which is not contained in the seed, but is the 
result of the reciprocal action of water and an albuminous substance in the 
seed, named myrozine by Bussy, upon another crystallizable principle in it, 
myronic acid, which is soluble in water, and appears to be an acid, although 
little is known respecting it. This oil is the cause of the acridity of black 
mustard. The application of boiling water to the mustard, of alcohol, acids 
or alkalies, which coagulate the albuminous body, prevent the formation of 
the volatile oil. 

This volatile oil is colourless, heavier than water, of a painfully intense 
odour exciting tears, and produces immediately inflammation and blisters 
when applied to the skin. Its boiling point is 289°. 4 (143° centig.) When 
burned, it produces sulphurous acid. When the oil and an excess of ammonia 
are put together in a well-stopped phial, the oil in a few days disappears, and 
a mass of beautiful crystals is found in its place, containing the elements of 
C 8 H 5 NS 2 -f-NH 3 . This compound is believed by MM. Dumas andPelouze, 



612 CAOUTCHOUC. 

who examined it, to belong to the class of amides. Oil of mustard is deprived 
of all its sulphur by distillation with hydrated oxide of lead, ammonia being 
formed with sulphuret of lead and another crystalline substance, sinapoline, 
C 23 H 24 N 4 4 , which also remains in the retort. (Simon.) 

To this class of essential oils also belong, oil of horseradish, from Cochlea- 
ria armoracia and C. officinalis, oil of garlic, from Allium sativum, oil of 
onions, from Allium cepa, oil of assafoetida, from Ferula assofcstida, oil of 
ivater pepper, Polygonum hydropiper, of Arum maculatum; also those of Le- 
pidium latifolium, and of hops, Humulus lupulus. 

The substances which follow are allied to the essential oils. 

Nicotianine, a volatile fatty matter obtained in minute quantity by distilling 
tobacco leaves with water. It is bitter and has a strong smell of tobacco. 

Asarine, from the root of Asarurn Europeam, a crystalline substance, fusi- 
ble in boiling water, volatile, having an aromatic smell and taste resembling 
camphor. Its composition is expressed by C l 6 H X1 4 (Blanchet and Sell.) 

Anemonine from Anemone pulsatilta, nemorosa and pratensis; a crystalline 
substance, C 5 H 2 2 (Fehling;) forms anemonic acid with barytes. (Lcewig.) 

Helenine, from Inula helenium; obtained by distilling the fresh root with 
water, or by acting on it with hot alcohol. It is crystallizable in white prisms, 
melts at 162°. and boils about 530°. Its formula is C l4 H 9 2 (Dumas,) or 
C 15 H 10 O 2 (Gerhardt.) With nitric acid and chlorine it yields two com- 
pounds, nitrohelenine, C r5 H 9 2 -f NO 4 , and chloride of helenine C, 5 H 10 2 
-f-Cl 2 . With anhydrous phosphoric acid, helenine yields a hydrocarbon 
C 15 H 8 . (Gerhardt, Ann. de Chimie, etc. lxxii, 163.) 

The wood of Quassia amara contains a crystalline body, so also do the 
pods of Epidendron vanilla, and the seeds of Tanghinia madagascariensis, 
the last highly poisonous, but none of them has been fully investigated. 

Caoutchouc or Indian rubber is the dried milky juice of several trees which 
grow in South America and the East Indies. The fresh juice was found by 
Mr. Faraday to contain 100 parts, 31.7 of caoutchouc, 1.9 of vegetable albumen, 
a trace of wax, 7.13 of an azotised substance, bitter, soluble of a brown colour 
in water and alcohol, and precipitable by nitrate of lead, 2.9 of a substance solu- 
ble in water, but insoluble in alcohol, and 56.37 parts of water containing in 
solution a small quantity of a free acid, which precipitated nitrate of lead and 
coloured persalts of iron green without precipitating them. These substances 
are dried and included in common caoutchouc, of which the density is 0.9335. 
Pure caoutchouc carefully prepared from the milk is of density 0.925, trans- 
parent and colourless, or of a light yellowish tint in mass. It contains no oxygen, 
but in 100 parts 87.5 carbon and 12.5 hydrogen, which are nearly in the pro- 
portion of C S H 7 (Faraday.) 

Caoutchouc is remarkable for its extraordinary elasticity, and its application 
to remove marks of black lead pencil from paper. It is soluble in pure ether ; 
a small bag of caoutchouc left in common ether for twenty-four hours is softened, 
and may then be greatly expanded by gradually inflating it, so as to become 
light enough to ascend in the air when filled with hydrogen gas (Mitchell.) 
Caoutchouc when cut into small pieces and well dried at 230°, is dissolved by 
rectified petroleum, and by the rectified oils from tar ; solutions which are exten- 
sively used as caoutchouc varnish. Caoutchouc also dissolves in the volatile 
and fat oils, but loses its elasticity in the latter. Oil of turpentine is often used 
in the preparation of caoutchouc varnish, to dissolve the caoutchouc, it is said, 
after it is softened and expanded by the naphtha. To render cloth air and 
water-proof, Mr. C. Macintosh first applied several coats of this varnish to one 
side of cotton or woollen cloth, and then bringing the varnished surfaces of two 
pieces together, passed the double cloth between heavy rollers, by which the 



RESINS. 613 

two pieces are made to adhere, and the interstitial spaces are completely filled 
up. The sheet caoutchouc used by chemists is obtained by sawing off a thin 
slice from a solid block of the material. In forming short connecting tubes 
of it, the sheet should be folded round the glass tube it is to fit, and the super- 
fluous edges cut close to the glass by sharp scissors ; the fresh surfaces being 
then brought into contact and pressed together adhere perfectly. 

Caoutchouc when heated to about 450° enters into fusion and forms a viscid 
adhesive mass. Distilled at a higher temperature, it yields a fluid product, 
which is a mixture of several hydrocarbons, differing greatly in volatility, the 
most volatile boiling at 90° ; and the least volatile at 680°. According to Himly, 
all these volatile oils are of the type C 5 H 4 > but from their examination by 
Gregory and by Bouchardat, some of them resemble olefiant gas or C 4 H 4 . 
Caout chine of Himly is one of these liquids, of which the boiling point was 
constant at 339°. Messrs. Enderby observed that the liquid distilled from 
caoutchouc is a solvent of that substance. 



» RESINS. 

From their endless variety, these bodies form one of the most extensive and 
indefinite classes of vegetable principles. Like the resin of turpentine, which 
may be taken to represent them, they flow from the tree dissolved in essential 
oils, which are removed by distillation with water. In the liquid or soft state, 
they are named balsams, which are all compounds or mixtures, like turpentine, of 
resin and essential oil. There is every reason to suppose a close relation in com- 
position between the oil and its associated resin, the last being often obviously 
the product of the oxidation of the former. The oxidation of the oil may occur 
by the combination of the entire oil as a radical with oxygen, or by the oxi- 
dation of hydrogen, and its removal from the oil in the form of water, and the 
replacement of the hydrogen lost by oxygen, in equivalent proportions. The 
point is not decided by the analytical information we at present possess, but 
M. Liebig adopting the following composition for : 

Oil of turpentine C 40 H 32 or C 20 H 16 
And for : 

Resin of turpentine C 40 H 30 O 4 orC 20 H 15 O 2 , 

prefers to represent the oil as the hydruret of a radical, or as C 2 H, 5 -f-H, which, 
like the hydruret of acetyl in olefiant gas is capable of combining directly with 
hydrochloric acid, and forming a double hydruret, C 20 H 15 4 HC1, or artificial 
camphor. The same hydruret is converted into the resia of turpentine by the 
oxidation and replacement of its atom of hydrogen by an atom of oxygen, 
making C 20 H ]5 -f-O, and the absorption of an additional atom of oxygen by 
this compound, making C 20 H 15 O 2 . 

Every natural resin is a mixture of several resins, quite as the essential oils 
are mixtures. They are separated from each other by their unequal solubility 
in hot or cold alcohol, in ether, in potash and carbonate of potash, or the diffe- 
rent solubilities of their compounds with metallic oxides in these and other men- 
strua. M. Unverdorben, who first threw light on the composition of the na- 
tural resins, separated from some five and more resins, all quite distinct sub- 
stances. They are heavier than water, and become negatively electrical when 
rubbed. Some of them which are slightly soluble in water, have a bitter taste, 
but most of them are quite insoluble in water, and tasteless. They are fusi- 
ble by a temperature above 212°, and are decomposed by a strong heat. Many 
52 



614 RESINS. 

resins, when dissolved, redden litmus, combine with bases and possess all the 
characters of acids, some even decompose alkaline carbonates. Others are 
neutral, and do not combine with bases. A large number of the resins have 
been examined and analyzed by Professor Johnston, to whose memoirs on the 
resins contained in the late volumes of the Philosophical Transactions, I must 
refer for information respecting individual resins* 

Amber is found in beds of wood-coal, and appears to be altered resin of the 
trees. It is a brittle, hard substance, usually nearly transparent, sometimes 
almost colourless, but commonly yellow or even deep brown, and often includes 
insects. Its density is 1.065. Amber is insoluble in water, alcohol dissolves 
about one-eighth of it, refusing to dissolve the rest. Alkalies also act only par- 
tially on amber. About 10 per cent, of amber is insoluble in ether ; what re- 
mains dissolves in oil of turpentine and naphtha. Amber thus appears to be a 
mixture of resins and a bitumen. 1 It contains also succinic acid, which is ob- 
tained from it by dry distillation. 



RESINOUS VARNISHES. 

Varnishes are made by dissolving resins in alcohol, or oil of turpentine, or in 
a mixture of oil of turpentine and a drying oil. These solutions, when spread 
upon a surface, evaporate, and leave it covered by a thin coating of the resin. 
To diminish the brittleness of spirit varnishes, a small quantity of Venice tur- 
pentine is added, which gives the coating of varnish a certain tenacity, or a little 
linseed oil, either alone or mixed with oil of turpentine. 

The least coloured varnish is that from copal, which is generally prepared 
by melting that resin, mixing it while hot with a little drying oil, and adding 
gradually to the mixture oil of turpentine, in quantity equal to the resin. 

Lac varnish or lacker applied to articles of brass, is made by heating to- 
gether : 

8 parts of shell lac 
4 parts of sandarach 
1 part of Venice turpentine 
4 parts of pounded glass 
60 parts of alcohol. 

The use of the pounded glass is simply to assist the solution of the pounded 
resin by preventing it from agglomerating into a mass, or sticking to the bottom 
of the vessel. This is an excellent varnish, but has a brown colour. 

The varnish usually employed to cover oil paintings, maps and engravings* 
is made of: 

24 parts of mastich 
3 parts of Venice turpentine 
1 part of camphor 
10 parts of pounded glass 
72 parts of oil of turpentine. 

The paper ought to be covered by a solution of isinglass, and dried, before 
the application of this varnish, which otherwise will sink into the paper, and 
make it transparent. 



RESINS. 615 



GUM RESINS. 



Many plants afford a milky juice when cut or pierced, such as the dandelion 
and poppy, which when exposed to the atmosphere, becomes solid, and assumes 
different appearances, according to the plant from which it is derived. These 
concrete juices form the gum-resins, which are important from their applications 
in medicine. They are essentially mixtures of resins with gum and an essen- 
tial oil. They form a milky liquid or emulsion with water, the gum only dis- 
solving, while the resin and oil remain in suspension together with various 
other matters with which they may be accompanied. Alcohol dissolves only a 
portion of them ; but dilute alcohol is their best solvent, as it takes up both the 
gum and resin. The dilute alkalies dissolve them completely, leaving nothing 
but foreign matter. In their number are, ammoniac, galbanum, assafcetida, oli- 
banum, myrrh, euphorbium, bdellium, aloes, scammony, gamboge, opium, lactu- 
carium, upas, and many others. Very few of them have much chemical interest, 
and their treatment properly belongs to pharmacy. 

The resinous acids produced by the action of nitric acid on aloes have lately 
been studied by Mr. E. Schunk ; they are remarkable for their splendid red and 
yellow colours, and form well crystallized salts. They are chrysolepinic acid, 
HO-f C 12 H 2 N 3 13 ; clirysamminic acid, HO + C 15 HN 2 12 ; with alselinic 
aud aloeresinic acids. (Liebig's Annalen, xxxix. 1.) 



CHLOROPHYL. 

This name is applied to the green colouring matter of leaves and plants in 
genera], which is observed floating in their cells in the form of green globules, 
Ether dissolves the colouring matter of these globules, leaving a colourless sub- 
stance, of which the nature is unknown. Chlorophyl is prepared by digesting 
fresh green leaves in ether, distilling off the latter, digesting the green residue in 
alcohol which dissolves it, distilling to dryness, and then digesting the chlorophyl 
in concentrated hydrochloric acid. The fine emerald green solution in that 
acid is precipitated by dilution with water. The precipitated chlorophyl is 
again digested in a concentrated solution of potash, and dissolved by the addi- 
tion of water. On saturating the last solution after filtration, with acetic acid, 
chlorophyl precipitates pure, in the condition of beautiful green flocks. 

Chlorophyl forms, when dried, a bluish-green mass, not fusible, insoluble in 
water, but dissolving of a fine green colour in alcohol, ether, concentrated sul- 
phuric and hydrochloric acids, and precipitated from these solutions by water. 
Its solution in alkali is green, precipitated by acids and not by water. Chlorine 
converts it first into a yellow substance, afterwards into a colourless fatty matter. 
Chlorophyl is intermediate in its properties between a fat and a resin. Exposed 
to the light of the sun, it becomes yellow, and is probably then identical with 
xanthophyl, the colouring matter of yellow leaves in autumn. 



616 NEUTRAL PRINCIPLES PECULIAR TO CERTAIN PLANTS. 



CLASS II. 

CONSTITUENTS OF PARTICULAR PLANTS, OR FAMILIES OF PLANTS. 

PIPERIN. 

Formula, C 34 H 19 N0 6 (Regnault.) 

This is a crystallizable principle in both white and black pepper first observed 
by M. Oersted ; but not the cause of the acrimony of pepper, which is due to a 
peculiar soft resin. Pepper is exhausted by means of hot alcohol, the solution 
distilled to the condition of an extract, and that mixed with dilute alkali, by 
which the acrid resin is taken up, and the piperin left undissolved as a greenish 
powder, to be purified by repeated crystallization from alcohol. 

Piperin forms rhomboidal prisms, of which the angles are 85°. 40' and 94°.20\ 
colourless, tasteless, inodorous, fusible at 212°, not volatile. It is scarcely solu- 
ble in water, and but slightly soluble in alcohol ; in cold sulphuric acid it dis- 
solves of a deep-red colour. 

ASPARAGIN. 

Formula, C s H r N 2 5 -f 2HO. 

A crystallizable substance, first obtained by Vauquelin and Robiquet, in the 
juice of asparagus ; it exists also in potatoes, liquorice root, and particularly in 
the root of Altliea officinalis, marsh-mallow, from which last it is generally pre- 
pared. The root is exhausted by means of cold water, the solution concen- 
trated by evaportion, and left for a long time in a cool place, for the crystal- 
lization of the asparagin. It forms pretty large, colourless, octohedral crystals, 
of a weak taste, soluble in 58 parts of cold water, insoluble in absolute alcohol, 
but more soluble in rectified spirits of wine than in water. These crystals lose 
12.13 per cent, of water at 194°. 

Heated with acid or alkaline solutions, asparagin is resolved into ammonia 
and aspartic acid, conducting itself thus like an amide. Heated with water 
alone, under pressure, above 212°, asparagin is converted into the aspartate 
of ammonia, by the assumption of 1 atom of water. The formula of anhy- 
drous asparamide is C 8 H 5 N0 5 4-NH,. 

Aspartic acid, H0-fC 8 H 5 N0 6 ; crystallizes in thin plates, slightly soluble 
in water, and possessed of weak acid powers.* 

SANTONIN. 

A crystallizable substance, obtained by Kcehler and by Alms from the seeds 
of Artemisia santonica, or southernwood. It is colourless and destitute of 
smell, requires between 4 and 500 times its weight of cold, and 250 times its 
weight of boiling water to dissolve it. It fuses about 276° without loss 



Wittstock in PoggendorfPs Anualen, xx, 346. 



CAFFEIN. 617 

of weight. The solution of santonin in alcohol reddens litmus, but its acid 
powers are weak. Its compound with potash, which has been named the 
santonate of potash, is decomposed when its solution is boiled for a few 
minutes, and the santonin deposited in crystals when the solution cools. It 
may be combined with other bases, but not without the agency of alcohol. 
Its analysis gave C 5 H 3 0, but its atomic weight is supposed to be twelve times 
as high (Liebig.*) 



ESCULIN. 

This substance is derived, by means of hot alcohol, from the chestnut-tree, 
ash, and probably other barks. It is in thin colourless plates, or a white 
powder, of a weak bitter taste, not fusible without decomposition. It is 
sparingly soluble in cold water. The solution, by exposure to light, acquires 
a beautiful blue colour, even when the quantity of esculin is very small; the 
blue tint vanishes with acids, but is revived by alkalies. The composition 
of esculin is expressed by C lc H 9 O 10 . 



PICROTOXIN. 

The substance to which eocculus indicus, the fruit of Menispermum coccu- 
lus owes its poisonous qualities, was first investigated by Boullay. It is 
obtained by boiling in alcohol the bruised seeds, after depriving them, by 
pressure, of the greater part of their fat oil, distilling off the alcohol, and dis- 
solving the remaining extract in boiling water, slightly acidulated, from which 
the picrotoxin crystallizes on cooling. 

It forms colourless, short and thin, prisms, is intensely bitter, and not fusi- 
ble. It is soluble in 25 parts of boiling water, and very soluble in alcohol: 
does not combine with acids. It is highly poisonous. Its composition is ex- 
pressed by C 12 H 7 5 (Regnault.t) 



ANTHIAR1N. 

The most deadly of the Upas poisons, employed by the inhabitants of the 
East Indian Archipelago to poison their arrows, is a gum resin, from the An- 
thiaris toxicaria, of which the active principle, anthiarin, was separated by 
MM. Pelletier and Caventou. It crystallizes in fine white plates, which are 
inodorous, sparingly soluble in water, more so in alcohol. It acts in the 
highest degree as a deadly poison. Its composition is C l4 H l0 O 5 . 



CAFFEIN. 

A crystalline substance is obtained from coffee, from tea, and from guarana,. 
a prepared mass from the fruit of Pairflinia sorbilis. To obtain it from coffee, 
the raw beans, well dried, are reduced to powder, and exhausted by boiling 
hot water; subacetate of lead is added to the infusion, to precipitate gum and 
other matters, the liquid filtered, and the excess of lead thrown down from it 
by sulphuretted hydrogen. After filtration, the liquid is concentrated by eva- 

* Tromsdorff Jun.; Liebig's Annalen, xi, 190. 

f Pelletier and Couerbe; Ann. de Chim. et de Phys. liv, 181» 

52* 



618 VEGETABLE ALBUMEN AND LEGUMIN. 

poration; tha caffein crystallizes on cooling, and is purified by a second crys- 
tallization. It may be obtained by boiling tea-leaves in water, filtering and 
proceeding precisely as with coffee, and also from guarana. It is snow-white, 
and in fine needles, having a silky lustre, which have a very weak bitter 
taste; does not act upon vegetable colours, and is sparingly soluble in cold 
water and alcohol. It loses 8 per cent, of water at 212°, fuses at 352° (178° 
centig.,) and sublimes at 725° (385° centig.) From its solution it is precipi- 
tated only by tannin. Boiled in a solution of caustic potash, it is resolved 
into carbonic acid, formic acid and ammonia. With sulphuric acid and 
hydrochloric acid, it forms crystalline compounds. According to the analy- 
sis of Liebig, crystallized caffein consists of C 8 H 5 N 2 2 + HO. The quan- 
tity of this substance in different kinds of cofTee was found by MM. Robiquet 
and Boutron to vary; Martinique coffee containing 6.4 per cent, and St 
Domingo cofTee only 3.2 per cent, of caffein. It is evidently not the principle 
upon which the peculiar properties of either cofTee or tea depend. 

Caffeic acid was discovered in cofTee by Runge. It is a white powder, 
which yields, when heated, the characteristic aromatic odour of roasted cof- 
fee. 

Coumarin is a neutral substance, extracted from the Tonka bean, the fruit 
of the Coumarouna odorata, and the flowers of the melilot, Melilotus offi- 
cinalis, which crystallizes in silky needles, or short prisms. Its composi- 
tion according to M. Henry is C 10 H 3 O 2 . 

Hesperidin, a crystalline substance, obtained by M. Lebreton from the skin 
of the unripe orange or lemon. 

Populin, found by Braconnot, in the bark of the Populus tremula, where 
H is accompanied by salicin. It crystallizes in snow-white silky needles, has 
a sweet taste, not unlike that of liquorice, requires about 2000 times its weight 
of cold water to dissolve it, but dissolves in about 70 times its weight of boil- 
ing water.* 

Plumbagin, discovered in the root of the Plumbago europa. 

Baphnin, extracted by Gmelin and Baer from the bark of the Daphne 
mezeriwn, or common mezerion. It is crystalline, colourless, but little solu- 
ble in cold water, soluble in alcohol and ether. Nitric acid converts it into 
oxalic acid. It is considered by Gmelin and Baer as a body analogous to 
asparagin. 



VEGETABLE ALBUMEN AND LEGUMIN. 

When fresh gluten from wheaten flower is digested in hot alcohol, till 
every thing soluble is taken up, vegetable albumen is left, of a grayish colour. 
It is soluble in water, and is coagulated by heat, insoluble in alcohol and ether, 
and agrees perfectly in properties with animal albumen. 

Braconnot observed a peculiar principle in the fleshy cotyledons of the 
seeds of papilionaceous plants, to which he gave the name legumin. Ripe 
peas, softened with water and reduced to a pulp, gave, when mixed with 
pure w r ater, a milky liquid, from which starch precipitated, and which re- 
tained legumin in solution, seemingly combined with a vegetable acid. When 
evaporated by heat, the solution does not coagulate, but deposites the legumin 
bv little and little, under the form of diaphanous pellicles. It is purified by 
washing it, while still moist, with boiling alcohol. It then has a fine white 
colour, and does not affect litmus paper. Legumin is soluble in water, but 

* Ann. et de Phys. t. 44, p. 296. 



INDIGO. 619 

insoluble in aleohol. It dissolves very readily in acetic, oxalic, citric and 
other vegetable acids, but is precipitated from solution, on the contrary, by 
the mineral acids which last, form sparingly soluble compounds with legu- 
min. Alkaline hydrates and carbonates also dissolve it with facility, and the 
solutions froth like a soap. 

M. Liebig has lately made the interesting observation that legumin is iden- 
tical in properties with the animal principle casein, and has the same com- 
position. It is also accompanied by the same salts, namely potash, phos- 
phate of potash, magnesia, lime and oxide of iron, as the casein of milk. 



NEUTRAL COLOURING MATTERS. 



INDIGO 

Formula of blue indigo, C, 6 H.N0 2 . (Crura. Dumas.) 

This important colouring matter exists in the leaves of all the species of the 
Jndigofera. It is obtained also from Nerium tinctoHum, and in small quan- 
tity from halts tinctoria (pastel or vvoad,) and various other plants. In India, 
the indigofera plants are cut before flowering, and allowed to steep for nine 
or twelve hours in a vat, covered with water, in which fermentation occurs 
with the evolution of carbonic acid and hydrogen gas. A yellow coloured 
liquor is drawn off into another vat, in which it is beat and stirred till it ac- 
quires a blue colour, and the indigo precipitates. It is then drained on calico, 
placed on proper frames, and strongly pressed by means of screws, cut into 
cakes of the proper size, and dried.* The plant thus appears to contain the 
indigo in a very different state from that in which it is ultimately obtained. It 
is not certain that it can be extracted from the indigofera without fermentation; 
but Chevreul has shown that it may be extracted from pastel, by treating the 
latter with hot water free from oxygen, and that the yellow solution thus ob- 
tained became blue, and deposited indigo. 

The indigo of commerce is of a deep-blue, inclining to black; its fracture is 
earthy and dull, but becomes of a coppery red when rubbed with a hard body, 
and the more brilliant and like copper the colour developed by friction, the 
purer is the indigo considered. It is far from being a pure substance, rarely 
containing half its weight of blue colouring matter, and often much less. Ber- 
zelius separated from it; 1, gluten of indigo, by digesting indigo in fine powder 
with a dilute acid, which also dissolves some salts of lime and magnesia ; 2, a 
principle which he has named indigo-broivn, by means of a concentrated solu- 
tion of caustic potash gently heated; and 3, indigo-red, by afterwards boiling 
the indigo repeatedly with alcohol of density 0.830. Indigo blue remains, but 
is not yet absolutely free from foreign matter. 

To obtain it pure, recourse is had to the solution of indigo in the ordinary indi- 
go vat, or the indigo purified by the preceding processes may be dissolved by 
imitating on a small scale the preparation of the dyer. One part of indigo in 
an impalpable powder and 2 parts of quick-lime, recently slaked, are mixed, 
and introduced into a well stopped bottle with about 150 parts of water. To this 
is then added two-thirds of the weight of the lime of crystallized protosulphate 
of iron in fine powder, or dissolved in a small quantity of hot water. The bottle 
then being completely full and well closed, is agitated occasionally for several 
hours, and kept in a warm place till the supernatant liquor acquires a yellow 
colour. The protoxide of iron precipitated by the lime becomes peroxide, taking 

* Dr. Thomson's Organic Chemistry, Vegetables, p. 369. 



620 NEUTRAL COLOURING MATTERS. 

oxygen from the blue indigo, which in this altered state forms a compound with 
the lime, soluble in water. When the yellow solution of this compound is 
poured out or exposed to air, it rapidly becomes blue from the absorption of 
oxygen, the indigo loses its solubility and precipitates. In the usual process of 
dyeing, the indigo is fixed by dipping the yarn or cloth in the same solution of 
indigo, and then exposing it to air ; the indigo thus penetrates into the cloth in 
a soluble state, and is rendered insoluble afterwards by oxidation within its 
substance, so that it cannot afterwards be washed out. The sediment in the 
bottle yields more soluble indigo, when agitated again with pure water slightly 
heated, or with lime-water. The yellow solutions are mixed together and freely 
exposed to air, with the addition of a little hydrochloric acid to dissolve the salts 
of lime, and the blue indigo which precipitates is collected, washed upon a filter 
and dried. It is afterwards washed with boiling alcohol by M. Dumas to take 
up the indigo-red of Berzelius. 

The purified indigo, when dry, is of a deep blue, with a shade of violet, and 
when rubbed, exhibits a strong copper red colour and metallic lustre. It is 
tasteless, inodorous, insoluble in water, alcohol, ether, and not affected by alka- 
lies or diluted acids. When heated to about 550°, it fuses (Crum,) and at the 
same time emits a beautiful purple red vapour and sublimes, condensing in 
small copper-coloured prisms, but it is always partially decomposed at the same 
time. To observe the beautiful appearance of sublimed indigo, ten or twenty 
grains of good indigo in powder may be put upon a pretty thick sheet of iron 
or copper, pressed flat and then covered by the lid of a platinum or porcelain 
crucible, two or three inches in diameter, while the plate is heated sharply by 
placing it over a lamp or choffer. On raising the cover, after the plate is cool, 
the charred mass will be found entirely covered by copper-coloured crystals. 
Their density is 1.35. Blue indigo was carefully analyzed by Mr. Crum* and 
repeatedly by M. Dumas, whose results confirm the original determination of 
Mr. Crum.f 

White or reduced indigo is produced by the action upon blue indigo of de- 
oxidating bodies of all kinds, such as the protoxides of iron and tin, sulphites 
and phosphites and many sulphurets, particularly the sulphuret of arsenic or 
orpiment, but only with the concurrence of an alkali or alkaline earth, which 
may combine with the reduced indigo. On neutralizing a solution of the alka- 
line compound with hydrochloric acid, carefully excluding air, the reduced 
indigo is thrown down as a white precipitate, flocculent, and composed of 
minute crystalline plates. Carefully dried in vacuo, it is coherent, of a grayish 
white colour and silky lustre; in the dry state it soon becomes blue superficially 
in the air, but requires several days to become entirely blue. When humid or 
dry, it is tasteless, inodorous, insoluble in water, soluble in alcohol and ether, 
which it colours yellow; but it is soon deposited from the alcoholic solution as 
blue indigo, when exposed to air. White indigo does not affect litmus, dis- 
solves in alkalies without neutralizing them, and has not marked acid characters, 
although it combines with bases. According to the observations of Dumas, 
the conversion of white into blue indigo occurs in air without any change of 
weight, or there is, at the utmost a slight but sensible loss. 

White indigo was named indigogen by Liebig, and blue indigo considered 
the oxide of that radical. M. Dumas takes another view of the relation be- 
tween these bodies, considering white indigo not as deoxidized blue indigo, 
but blue indigo combined with an atom of hydrogen, and forming a hydruret, 
analogous to the hydruret of benzoyl, thus: 

Blue indigo . . . C l6 H 5 N0 2 . 
White indigo . . . C lfi H 5 N0 2 -fH. 



* Thomson's Annals of Philosophy, second series, v. 82. 

i Dumas, Ann. de Chim. et de Phys. t 73, p. 269 ;, and 3 s6r. t. 2, p. 204. 



INDIGO. 621 

In the oxidation of indigo, on this view, water is formed and liberated. M. 
Dumas still adheres to this view in his late Memoir on indigo. The combus- 
tion of white indigo he found to be easily affected, but of blue indigo is attended 
with difficulty, so as to leave some uncertainty as to its composition. Ac- 
cording to M. Erdmann, the formula of blue indigo is C 32 H 10 N 2 O 3 . 

Action of sulphuric acid. — Indigo combines with fuming sulphuric acid or 
oil of vitriol, when slightly heated with that acid in the proportion of 1 to 8, 
without any evolution of sulphurous acid, and forms a semi-fluid mass, popu- 
larly known as sulphate of indigo, which dissolves in a considerable quantity 
of water, of an intense blue colour. The products of this action were first 
examined by Mr. Crum, whose results form the basis of M. Dumas' later in- 
vestigations. To convert blue indigo into sulphindilic acid, the latter chemist 
recommends the digestion of the indigo in a large quantity, not less than 15 
parts, of concentrated oil of vitriol, for three days in a bath maintained at a 
temperature of 120° or 140°. The solution is afterwards diluted with water 
and filtered, although when these precautions are attended to, little or nothing 
insoluble remains on the filter. To the limpid liquid a strong solution of pure 
acetate of potash is added, and the precipitate which falls is washed with ace- 
tate of potash, in which salt the sulphindylate of potash is insoluble although 
soluble in water; the acetate of potash remaining in the precipitate is got rid 
of by diffusing the latter through a quantity of ordinary alcohol and filtering 
again. The blue matter remaining when well dried at 212°, gave by analysis, 
KO-f-C l6 H 4 NO,S 2 6 ; conducting to the following formula for hydrated sul- 
phindylic acid, HO-j-C, 6 H 4 NO,S 2 6 . Blue indigo thus appears to lose 
HO in the formation of sulphindylic acid. Sul/thopurpuric acid, remains 
upon the filter in the preparation of sulphate of indigo, when 8 or 10 parts 
only of sulphuric acid have been employed to 1 of indigo. It is drained and 
washed with diluted hydrochloric acid', till the washings are colourless and free 
from sulphuric acid. It is then carefully dried about 392° (200° centig.) This 
purple acid gave by analysis, C 32 H 1 N 2 O 4 -f2SO 3 . The sulphopurpurate 
of potash is obtained by dissolving the acid in water, and adding acetate of 
potash to the liquid; it precipitates in purple flocks, which should be washed 
first with a solution of acetate of potash, and then with alcohol. Its compo- 
sition indicates that the atom of indigo C ]6 II 5 N0 2 takes the isomeric state 
C : , 2 H ]0 NO 4 , to constitute sulphopurpuricacid. M.Dumas institutes the fol- 
lowing comparison between the indigo and benzoyl compounds: 

C 16 H,N0 2 Blue indigo C 14 H 5 (X Benzoyl 

C lC H 5 N0 2 ,H White indigo C ]4 H 5 CK,H Essence of bitter almonds. 

C 16 H,N0 4 Isatin of Laurent C ]4 H 5 4 Salicyl. 

C 14 H 5 4 ,H Hydruret of salicyl. 

Action of fused potash on indigo. — M. Gerhardt has made the curious ob- 
servation that when blue indigo is thrown in small portions into fused hydrate 
of potash, that body dissolves losing its colour, disengaging abundance of hy- 
drogen and ammoniacal gas, and leaving as a fixed residue a mixture of valerate 
and carbonate of potash. The reaction takes place at the expense of the ele- 
ments of water; 1 atom of indigo with 14 atoms of water giving 1 atom of 
valerianic acid, 6 atoms of carbonic acid, 1 atom of ammonia and 6 atoms of 
hydrogen. On heating the saline residue slightly with sulphuric acid, valerianic 
acid is obtained in large quantity. This indeed appears to be the most eligible 
process for preparing that acid. 

Indigo is much used in dyeing, being principally applied in the deoxidized 
state, and forms one of the most permanent colours, resisting every thing ex- 
cept chlorine and nitric acid. In the form of sulphate of indigo, it is used for 
Saxon blue, which is much less permanent. 



622 NEUTRAL COLOURING MATTERS. 

Jinilic or indigotic acid, HO-f C 14 H 4 N0 9 (Dumas ;) is formed when indigo 
is dissolved in nitric acid considerably diluted, and may be crystallized by con- 
centration of the liquid. It forms colourless prisms, of a sourish bitter taste, fu- 
sible and volatile, sparingly soluble in water. It forms crystallizable salts, which 
detonate feebly when heated. The formula of the salt of silver is Ag0 + C 14 
H 4 N0 9 (Dumas.) The indigo therefore in forming anilic acid with nitric acid, 
loses 2 atoms of carbon and 1 of hydrogen. 

Picric acid, carbazotic acid, HO-fC 12 H 2 N 3 O l3 (Dumas.) This acid, 
which was first known as the bitter of Welter, is produced by the action of 
nitric acid on the preceding compound, and by the solution of indigo or any 
other azotised organic substance in concentrated nitric acid. It crystallizes in 
yellow brilliant prisms, of a very bitter taste, which are fusible and volatile, and 
burn with flame when sharply heated ; they are sparingly soluble in water, 
which they colour yellow. Picric acid is not decomposed by other acids nor 
by chlorine. Its salts are yellow and generally crystalline ; they detonate 
strongly when sharply heated, or sometimes by a blow, particularly the potash 
salt. M. Piria has also observed the formation of picric acid in the treatment of 
hydruret of salicyl with nitric acid. 

Chlorisatin, C 32 H 4 NC10 3 .* When chlorine gas is transmitted through 
water in which blue indigo is suspended, hydrochloric acid is formed, and the 
indigo is converted into a reddish yellow matter, which Erdmann has found to 
be a mixture of several new products, of which the most remarkable are two 
chlorine compounds, which have been named chlorisatin and bichlorisatin. 
When the yellow matter is digested in boiling water, a resin is left undissolved, 
and a solution formed, which on cooling, deposits a reddish yellow crystalline 
powder, which is a mixture of the two compounds mentioned. When this is 
dissolved in boiling alcohol, the chlorisatin crystallizes out first. It forms 
orange-yellow, four-sided prisms, is bitter, soluble in alcohol, but highly insoluble 
in cold water. It is partially decomposed by sublimation. 

Chlorisatin dissolves in a solution of caustic potash, of a red colour. When 
heated, the colour of this solution changes to yellow, and a potash salt crystal- 
lizes on cooling, in shining plates, of which the composition is K0 + C 32 H 5 NC1 
4 . It contains chlorisatinic acid, into which under the influence of bases, chlo- 
risatin is converted, by the fixation of the elements of an atom of water. Strong 
acids throw down chlorisatin again from the potash salt. The salt of lead is a 
yellow precipitate, which becomes of a fine scarlet on standing. The salt of 
copper is thrown down brownish yellow, but becomes blood red and granular. 

Bichlorisatin , C 3 2 H 4 NC1 2 3 ; contains twice as much chlorine as chlorisatin, 
but greatly resembles it in properties, and is analogous in its relation to alkalies. 
The salt of lead of its acid is permanently yellow ; the copper salt, which first ap- 
pears as a brown gelatinous precipitate, soon becomes greenish yellow, and 
then of a splendid blood-red and granular. It is said to form a very fine red 
on drying, and to take a gold lustre by friction. 

Chlorisatyde, C 32 H 5 NCl0 3 ; a white substance which is formed when sul- 
phuretted hydrogen is sent through a solution of chlorisatin in alcohol ; the liquid 
becomes colourless, and sulphur is precipitated at the same time. Bichlorisatin 
in similar circumstances yield fiichlorisatyde, C 32 H 5 NC1 2 3 . When treated 
with potash chlorisatyde and bichlorisatyde yield chlorisatydic and bichlorisa- 
tydic acids. 

Chloranile, C 6 Cl 2 2 , one of the products of the continued action of chlorine 
upon chlorisatin and bichlorisatin dissolved in alcohol. It is a volatile substance 
in crystalline scales of a brass yellow colour, which is dissolved by potash of a 

* So named from Isatis tivctoria. These formulae are to be considered with reference 
to the formula ascribed to blue indigo, by M. Erdmann, namely C 32 H l0 N 2 Q 3 . 



INDIGO. 623 

purple colour, but is then converted into chloride of potassium and chloranilate 
of potash. Chloranilic acid is a reddish powder, composed of fine scales; its 
composition is C 6 C10 3 . 

Chrysani/ic Acid, HO-f C 28 H 10 N 2 O 5 . When indigo in powder is added 
to a solution of caustic potash, of density 1.35, and boiled in a silver vessel, an 
orange-yellow salt is formed, without any evolution of gas. The acid is sepa- 
rated as a reddish-brown precipitate on the addition of sulphuric acid to a so- 
lution of the potash salt ; it is named chrysanilic acid, from its relation to ani- 
line and the golden-yellow colour of its salts. (Fritsche.) 

Mnthranilic acid, HO-j-Cj v H 6 N0 3 . The solution of the fused mass above 
becomes blue in the air from absorption of oxygen, like a solution of white indi- 
go, and blue indigo precipitates in crystalline grains. On boiling the solution 
with dilute sulphuric acid, the decomposition proceeds more rapidly, and a brown 
resinous mass is obtained, soluble in alcohol, ether, and alkalies. To prepare 
this acid, the first alkaline solution is diluted, and peroxide of manganese added 
to it in small quantities, at the boiling point, till the solution gives no black pre- 
cipitate when rendered acid, and its colour is not reddish-brown but a dirty 
grayish brown. This acid, when sublimed, is white and resembles benzoic acid, 
but the fused sublimate is yellow. Its salt of lime is very soluble in hot water, 
and crystallizes in colourless rhombohedrons. Anthranilic acid distilled by the 
heat of a spirit lamp, is decomposed in a considerable measure, and resolved 
into carbonic acid and aniline. (Fritsche ; Liebig, Annalen, &c., xxxix. 76 
and 91.) 

A nilino, C, 2 H 7 N (Fritsche ;) an oily liquid which distils over when finely 
pulverized indigo is decomposed by a highly concentrated solution of caustic- 
potash or soda in a retort. Its quantity amounts to about 18 or 20 per cent, of 
the indigo employed. The density of aniline is 1.028, it boils at 442°. 4 (228° 
centig.) Its smell is strongly aromatic, but at the same time disagreeable, it is 
sparingly soluble in water, but mixes in all proportions with alcohol and ether. 
Exposed to the air, it acquires a yellow colour and becomes resinous. The 
most remarkable property of aniline, is its basic character. It forms salts with 
acids assuming an atom of water when it unites with oxygen acids, and com- 
bining directly with hydracids, exactly like the vegeto-alkalies and ammonia. 

Oxalate of aniline is formed by mingling together alcoholic solutions of 
aniline and oxalic acid ; it falls as a white powder, which is to be washed 
with alcohol, from which it crystallizes on cooling. Its formula is C, 2 H 7 A -f 
HO,C 2 O r Hydrochlorate of aniline is prepared by mixing aniline with hy- 
drochloric acid, and crystallizing the salts ; it dissolves easily in water ; its 
formula is C, 2 H-N-f HC1*. 

Unverdorben had previously obtained, among the empyreumatic products of 
the dry distillation of indigo, an oily alkaline body, which he had distinguished 
as crystalline, because it has the property of forming crystallizable salts with 
acids, it was not analyzed, but there can be little doubt that it is identical with 
aniline. 



COLOURING PRINCIPLES OF ARCHIL, LITMUS, AND CUDBEAR. 

Various lichens, which communicate no colour to pure water, strike a fine 
blue with solution of ammonia. They contain certain crystallizable principles, 
in themselves colourless, which are thus modified by assuming the elements of 
ammonia. The history of these principles is still incomplete, although consider- 
able progress has been made in their investigation by the labours of Robiquet, 

* Fritsche in Liebig's Annalen, xxxvi, 84. 



624 NEUTRAL COLOURING MATTERS. 

Heeren, Dumas, Kane, and E. Schunk. The limits of this work will not permit 
me to enter into details respecting the various bodies obtained, of which I can 
do little more than indicate the names and the composition when determined. 

From archil weed, the Roccella tinctoria, Dr. Kane obtained the following se- 
ries of substances, either existing in the lichen or produced by the action of re- 
agents upon principles existing in it. 

1. Erythrilin, C 32 H, fi 6 ; a white powder* insoluble in water, but converted 
by ebullition into erythrilin bitter, soluble in alcohol and ether, also in alkaline 
liquids, from which it is precipitated by an acid ; not volatile. 

2. Erythrin, C 20 H^ 3 9 ; sparingly soluble in cold water, but very soluble 
in boiling water, and separating on cooling in brilliant, micaceous, snow-white 
scales ; the solution is colourless, but in air becomes rapidly brown, and is de- 
composed. It is very soluble in alcohol, ether and alkaline solutions, from 
which it is precipitated unaltered by an acid. It fuses at 220° without losing 
water, and is decomposed at a higher temperature without volatilizing. This 
substance agrees in composition and properties, and is believed by Dr. Kane to 
be identical with the pseudo-erythrin of Heeren, derived from the Parmelia 
roccella. It forms a wine-red solution when exposed to the conjoint action of 
ammonia and air. 

Erythrin bitter, amarythrin, C 22 H 13 14 ; is formed when erythrin is dis- 
solved in hot water and exposed some days to the action of air. It is a bitter 
extractive matter, very soluble in water, much less so in alcohol, and not at all 
in ether. It is precipitated, like the preceding compounds, by a salt of lead. This 
is the erythrin bitter of Heeren. 

4. Telerytrin, C 2g H 9 1 8 ; formed when amarythrin, in a semi-fluid state is 
exposed for several months to air, the latter changing gradually into a mass of 
very minute granular crystals, of a brownish yellow colour, but becoming white 
when purified by crystallization from alcohol. 

The ordinary archil (orseille) of commerce is prepared from the Parmelia 
or Roccella. The lichens are reduced to a pulp, and treated with impure am- 
moniacal liquors. The complete production of archil requires a considerable 
time, and from Dr. Kane's observations, the colouring matter is in a constant 
state of transition. 

Orcin (cr.,) C 18 H )2 8 ; a colourless crystallizable substance, obtained by 
Robiquet from the Lichen dealba/u*. The dried lichen is boiled with alcohol, 
the solution filtered hot, and distilled to the condition of an extract ; the last is 
exhausted by water, and the concentrated solution brought by evaporation to 
a state for crystallization. The orcin is purified by treatment with animal char- 
coal and repeated crystallization. It forms colourless, four-sided prisms, of a sweet 
but disagreeable taste, soluble in water and alcohol, easily fused and volatile. 
Its most characteristic property is the becoming of a deep violet colour, when 
exposed to the joint action of ammonia and air, owing to the formation of orcein. 
Orcin forms a compound with oxide of lead, of which the formula is C 1 a H 7 3 -f 
5PbO. 

Orcein. — The orcein of archil is of a fine red colour, slightly soluble in water, 
but colouring it strongly, and wholly precipitated from it by the addition of a 
neutral salt. It is very soluble in alcohol, which it colours scarlet, and from 
which water precipitates it. It is scarcely soluble in ether. Orcein dissolves 
easily in potash or ammonia, giving it a magnificent purple colour, the colour 
of ordinary archil ; from this solution, the colouring matter may be separated 
by the addition of an excess of common salt. An alkaline orceinate gives with 
metallic salts, lakes of a fine purple of different shades, which, however, lose 
much of their lustre in drying. , Dr. Kane finds the orcein of archil to be often 
a mixture of two substances, differing in their proportion with the age of the 
archil which he names alpha-orcein and beta-orcein ; the last is produced by 



INDIGO. 625 

the oxidation of the first, and is the orcein of Robiquet and other chemists. 
Their formulae are : 

Alpha-orcein . . C 18 H 10 NO 5 (Kane.) 
Beta-orcein . . C 18 H 10 NO 8 (Liebig, Kane.) 

The last was dried before analysis at 212°. The formulae of their compounds 
with oxide of lead are : that of alpha-orcein, C x 8 H 10 IVO 5 -f 3PbO, and that of 
beta-orcein, C 18 H 10 NO 8 + SPbO. The two orceins are identical in all their 
essential chemical properties; have the same solubility in water, alcohol and 
ether. The formula of anhydrous orcein being Cj 8 H 7 3 , that substance re- 
quires only to combine with 1 atom of ammonia, together With 2 or 5 atoms of 
oxygen, to form the one or other variety of orcein. 

In addition to the two orceins, the archil of commerce contains erythr oleic 
acid and azoerythrin, of which the former admits of two modifications ; besides 
the yellow matter of Heeren. 

Azoerylhrin consists of C 22 H I9 22 (Kane,) by abandoning 4 atoms of car- 
bonic acid and 9 atoms of water, it will yield an equivalent of alpha-orcein. 

Erythroleic acid, C 2G H 22 8 (Kane,) is a purple substance, distinguished for 
its semi-fluid consistence at the ordinary temperature, and its solubility in ether 
and alcohol. 

Roccellic acid, C, 6 H 1 6 4 (Liebig,) one of the principles extracted by Heeren. 

Litmus. — The cubical masses of commercial litmus being reduced to powder 
and treated with boiling water give a deep-blue solution. The mass of insoluble 
matter, which is of a paler blue than the original substance, is diffused through 
water and reddened with hydrochloric acid. The whole is then thrown upon 
a filter, and the red insoluble substance which remains is washed with water 
until all excess of hydrochloric acid is removed and then carefully dried. The 
mass when completely dry is boiled in successive portions of alcohol, until 
every thing soluble in that liquid i3 taken up. The deep-red alcoholic liquors 
are then distilled in a w 7 ater-bath to dryness, and the resulting solid material 
digested in warm sulphuric ether until the latter no longer becomes coloured. 
The ethereal solutions thus obtained, yield on distillation in a water-bath a fine 
crimson oily material which is nearly fluid. When purified, this matter forms 
erythrolein, C 26 H 22 4 . This compound is completely liquid at 100°; its solu- 
tions in alcohol and ether are of a fine red colour, and it tinges water pink, 
without however dissolving in any very sensible proportion. 

The substance from which the erythrolein has been removed, and which is 
distinguished by its solubility is erythrolitmin, C 26 H 22 12 -f HO; it is of a 
bright red colour, sparingly soluble in water, which it colours red. It dissolves 
of a blue colour in potash, and combines with ammonia. 

The brownish-red mass which resisted the action of alcohol, yields its colour- 
ing material but very sparingly to water also ; but it may be dissolved in a large 
quantity of boiling water, and gives by evaporation a deep blood-red mass, 
consisting of pure colouring material, which has been named azolitmin, Cj 8 Hj 6 
NO 10 ; it differs only from alpha-orcein and beta-orcein in the proportion of 
oxygen it contains. 

Another substance occasionally but rarely present in litmus is spaniolitmi/i 
C 18 H 7 16 . It is of a bright-red colour, insoluble in alcohol and in ether, and 
very sparingly soluble in water, w T hich it tinges bright-red. 

The blue liquors which are obtained in the first place by digesting litmus 
cakes in water contain but a small quantity of colouring matter, considering 
their depth of tint. It is generally azolitmin nearly pure ; with occasionally a 
small portion of spaniolitmin. 

By the action of chlorine upon orcein, chlororcein is formed, C x B U 1 NO 8 iG, 
53 



626 NEUTRAL COLOURING MATTERS. 

which possesses a yellowish-brown colour. With azolitmin a similar compound 
of chlorine is produced, C t 8 U 1 NO 1 ,C1. By the action of nascent hydrogen 
upon orcein, a colourless body is formed, levcorcein, C t 8 H 10 NO 8 ,H. For all 
these facts we are indebted to Dr. Kane (Phil. Trans. 1840, p. 298.) 

Cudbear, in German persio, is prepared from the Le.conora tartarea, Par- 
wnelia omphalodes, and probably other lichens. The lichen is steeped and left 
for some time in open vessels covered by ammonia, till the purple colour is suf- 
ficiently developed, and then the whole is dried in the open air and reduced to 
a fine powder. 

Mr. Schunk has lately obtained by extraction with ether from the Leconora 
tartarea and other lichens employed in the manufacture of cudbear a white 
crystalline substance leconorin, which is dissolved by alkalies and precipitated 
again unaltered by acids. But if the alkaline solution is allowed to stand for an 
hour, no precipitate is afterwards obtained, the new substance having resolved 
itself into carbonic acid and orcin. When the solution of the new substance in 
barytes-water is heated to the boiling point, carbonate of barytes precipitates 
and the solution yields by evaporation large crystals of orcin. It is probable 
therefore that orcin does not exist read}?- formed in any lichen, but is always the 
product of the action of an alkali, a circumstance which has hitherto been over- 
looked. 

Litmus is much used as a re-agent from its susceptibility to the action of acids 
and alkalies, being reddened by the former and having its blue colour restored 
by the latter. In preparing litmus paper an infusion is made of commercial 
litmus, filtered, concentrated by a water-bath, and a very small quantity of car- 
bonate of soda added. Good letter paper cut into slips of three inches in breadth 
is dipt into the infusion, allowed to dry and the dipping repeated ; or the infusion 
may be applied to one side only of thin and sized drawing paper. B'or red 
paper, the infusion of litmus is acidulated slightly by means of acetic acid. A 
paper prepared from an infusion of the best cudbear without the additiftn of 
either alkali or acid has a purple colour and is affected by both acids and alka- 
lies. It is convenient in alkalimetry, being already too red to be sensibly affected 
by carbonic acid, while it is distinctly reddened by the mineral acids. The 
colours from the lichens are beautiful, but fugitive ; they are chiefly employed- 
by the dyer to give a bloom to more fixed colours. 



COLOURING MATTERS OF MADDER. 

JHizarin,* C 37 H 12 O ]0 (Robiquet). — This is a crystalline matter of a red 
colour which was extracted by MM. Robiquet and Colin from the ground 
roots of madder, the Rubia tinctorum. To concentrated sulphuric acid an 
equal quantity of ground madder is added in a gradual manner, so as to pre- 
vent any sensible elevation of temperature; in two or three days nearly all 
the constituents of the madder are charred and destroyed except the aliza- 
rin. The acid is then washed out from the black mass, which is dried and 
digested with portions of cold alcohol, to take up a fatty matter it contains. 
The alizarin is afterwards dissolved out by boiling alcohol, the latter solution 
mixed with water, the alcohol distilled off, and the alizarin which has precipi- 
tated is collected on a filter.! It is a red powder, which may be sublimed 
and is obtained in long flexible capillary needles, having an orange colour; 
but unless the subliming vessels be very low and flat, almost the whole of the 

* From alizari the name applied to madder roots in the Levant 

+ Annates de Chimie et de Physique, tome 34, p. 228; and Journal de Pharmacie, tome 
21, p. 392. 



MADDER. 627 

alizarin is decomposed. Alizarin is somewhat soluble in boiling water to 
which it communicates a rose colour; at 54°, it dissolves in 212 parts of alco- 
hol and in 160 parts of ether. It has a decided affinity for some animal mat- 
ters, being soluble in albumen, and is precipitated in combination with the 
latter when coagulated. Phosphate of lime appears also to combine with the 
colouring matter of madder, from the well known fact that the bones of animals 
which have taken for some time madder mixed with their food, are tinged 
red. 

The colouring matter of madder has also been examined by Gaultier de 
Claubry and Persoz,* by H. Schlomberger,t and by Dr. F. Runge. i From 
their inquiries it is certain that alizarin is not the only or perhaps even the 
most important colouring matter of madder. These different inquirers have 
extracted various substances from madder, but do not agree in the mode of 
representing its constitution; as the purity however of these substances was 
not tested by analysis, their definite character is necessarily very doubtful. I 
can only enumerate here the different colouring matters extracted from mad- 
der by Dr. Runge. They are (1) Madder purple, dissolved out from madder, 
previously well washed with water between 56 and 70°, by a strong boiling 
solution of alum, and precipitated from the alum solution by the addition of 
sulphuric acid. When purified it is a light crystalline powder of a beautiful 
orange-yellow colour. When used in excess it imparts to cotton impreg- 
nated with the alum mordant, a deep reddish-brown purple colour; but if on 
the contrary the cotton be in excess, the colour is bright red. (2) Madder 
red, the alizarin of Robiquet and Colin, which according to Runge may be 
sublimed a second time without decomposition. It may be separated from 
madder purple, in consequence of its insolubility in a strong solution of alum. 
(3) Madder orange, which is distinguished and separated from the two for- 
mer, by its little solubility in spirits. When in excess it imparts to alumed 
cotton a bright orange colour. If water be added to a hot solution of it in 
spirit, small crystals separate, as with madder-red and madder-purple under 
the same circumstances. (4) Madder yellow is remarkable for its great solu- 
bility in water and its little affinity for cloth impregnated with alum. It 
abounds in Dutch madder. (5) Madder brown, another principle, which like 
the last has no value as a dye stuff. 

The most fast and brilliant reds are obtained upon cotton by means of mad- 
der, as also an equally stable and valuable purple; the first are known as 
Adrianople or Turkey reds. The colouring principles of madder have an 
affinity for the earth alumina and peroxides of iron and tin, like other organic 
colouring matters soluble in water, and form insoluble precipitates with these 
oxides, which are known as lakes. By impregnating cotton cloth with a 
solution of acetate of alumina, or with alum of which the acid has been in a 
great measure neutralized by an alkali, it retains a portion of that earth, (or of 
either the other metallic oxides mentioned if treated with a solution of their 
salts,) of which it is not deprived by washing; these oxides having an attrac- 
tion or affinity for the fibre of cotton. If the cloth so prepared be introduced 
into a hot solution of any organic colouring matter, the latter is taken up from 
the solution and becomes attached to the cloth by combining with its alumina, 
which thus forms the link that unites the cloth and colouring matter. The 
alumina is termed the mordant, and such is the ordinary method of fixing co- 
lours by means of mordants. Cotton may be dyed with madder by this sim- 
ple process, but the colour is dull. To produce a fine red the cloth must be 

* Ann. de chim. et de Phys., t. 48, 72. 

•f Bulletins of the Industrial Society of Mulhausen. 

t Dr. R. D, Thomson's Records of Science, vol. 2, p. 452, and vol. 3, pp. 44 and 135. 



628 NEUTRAL COLOURING MATTERS. 

submitted to a long preparation occupying some weeks, and consisting of a 
number of operations, the effect of many of which is very imperfectly under- 
stood, but every one of them nevertheless indispensable for a good result. 
The chief features of this remarkable process, without entering into a detail 
of the routine operations are (1) the impregnation of the cloth with an imper- 
fect soap and some principles from sheeps' dung. By this treatment, which 
consists of several operations repeated more than once, the cloth acquires an 
animal odour, which it retains through the rest of the operations. It is said 
that when old cotton cloth that has been worn about the person and frequently 
washed is to be dyed, this process may be omitted altogether. (2) The cloth 
is afterwards soaked in an infusion of nutgalls or of sumach, which gives it a 
yellow colour and assists also in fixing the madder afterwards, this is the 
galling^ an accessory operation not confined to madder dyeing. (3) Alumina 
is fixed in the cloth in the manner previously described. (4) The cloth is 
then dyed by entering it into a boiler with ground or chopped madder while 
the water is cold, gradually raising the temperature, and boiling them together 
for a couple of hours. A certain quantity of bullock's blood is also added to 
the madder bath. The colour thus fixed is brownish-red and dull, owing to 
the Madder brown being fixed in the cloth, as well as the madder purple and 
madder reel. The object of (5) the clearing process is to get rid of the brown 
which is not nearly so fixed as the red. It consists of boiling the cloth in 
alkali and soap; afterwards with soap and protochloride of tin under a pressure 
of two atmospheres, and finally exposing the cloth on the grass to the sun for 
a few days. 

If the cloth be prepared and dyed with madder in the same manner, with 
the exception of charging it with an iron instead of an aluminous mordant, it 
is dyed of a beautiful and permanent purple, instead of red,* 



CARTHAMIN. 

Safflower consists of the flowers of Carthamus tinclorius; it contains two 
colouring matters, a yellow, which is of no value, and a beautiful but fugi- 
tive red used in silk dying, which is named carthamin or carthamic acid. 
The yellow matter is soluble in water, the red insoluble in water but soluble 
in alkalies. They are separated by adding an acid to an alkaline infusion of 
safflower, which throws down the carthamin, and afterwards passing clean 
cotton yarn through the liquid; in these circumstances, the yarn takes up the 
carthamin entirely and is then washed with water. The pure carthamin is 
afterwards stript from the cotton by an alkali and the solution is employed to 
dye silk by acidulating with citric acid, and then passing the silk through the 
liquid in the usual way by means of a winch. 

The pigment rouge contains precipitated carthamin intimately mixed with 
finely divided talc, 

According to Doebereiner, carthamin has an acid reaction; it is but slightly 
soluble in alcohol or ether. Soda saturated with carthamin is said to crystallize 
in fine colourless needles having a silky lustre, and becoming instantly red 
when an acid is added, 

* An outline of the process of Turkey red dyeing as practised at Glasgow is given by 
Dr. Thomson, in his Organic Chemistry, Vegetables, p. 396. For this and other dying pro- 
cesses, see also Leuch's Traite complet de§ Matieres Tinctoriales. 



BREZILIN. 629 



HEMATOXYLIN. 

This is the colouring matter of logwood, the wood of the Hsematoxylon 
campeachianum; it was named Hematin by M. Chevreul,* who first distin- 
guished it. It is sometimes so abundant as to exist in the wood in large crys- 
tals. The rasped or chopped wood is exhausted by means of water of a tem- 
perature between 122° and 131°, the solution evaporated to dryness by a wa- 
ter bath, the residue lixiviated with alcohol of 0.843. density, and the filtered 
solution distilled to a syrup, from which after the addition of a little water the 
hematoxylin is gradually deposited. 

It crystallizes in reddish yellow scales, soluble in 1000 times their weight 
of water, dissolving easily in alcohol and ether. Acids in small quantity 
make it yellow, in large quantity red. The alkaline bases impart to a solution 
of hematoxylin a violet, purple or blue colour. Its decoction is deprived of 
colour by sulphuretted hydrogen (which has the same action on litmus,) and 
by nascent hydrogen; much of the hematoxylin probably exists in this state in 
the wood and acquires colour in the course of its application as a dye. Cloth 
impregnated with alumina is dyed black in a decoction of logwood, and of ft 
fine brown in a mixture of logwood and madder. It enters into the materials 
for dying hats and broad cloth black; the effect of an acid in staining them red 
is due to its presence. By dry distillation hematoxylin yields ammonia, 
proving that it contains nitrogen. 



BREZILIX. 

This name has been applied by Chevreul to the colouring matter of Brazil 
wood, which comes to this country from Brazil and Pernambuco, and is the 
wood of several species of Ccesalpina. It is obtained by similar processes 
with the preceding colouring matters. 

Brezilin crystallizes in orange prisms, soluble in water and alcohol. Acids 
give it a yellow colour; with citric acid the yellow is particularly fine. When 
neutralized with alkali it becomes again of a line red, but with an excess of 
alkali violet or blue. In the tree it is nearly colourless, owing to the presence 
of free acid, and its fine red colour does not appear till all the acid which it 
naturally contains is saturated. This saturation is generally effected by sprink- 
ling the ground wood with a solution of carbonate of soda, when its colour is " 
said to be raised. A very minute quantity of alkali gives an infusion of Brazil 
wood a violet colour, so that it is a delicate test of alkalinity. Alum and the 
acetate of alumina throw down from it an abundant carmine precipitate, while 
the liquid retains the same colour; these compounds form the basis of common 
red ink. For some years past brazil-wood has been nearly superseded in this 
country by a wood imported from Africa, and named camwood by dyers, 
which is richer and gives a finer colour than any of the varieties of Brazil 
wood. It is also not so much affected by alkalies, nor so liable to assume a 
violet shade; and the yellow colouring matter with which it is mixed gives 
the red a more lively appearance (Dr. Thomson.) But the colour of these 
and all other red woods has little permanence and does not produce fast 
colours. 

* Ann. de Chim. et de Phys., I. 81, p. 128. 
53* 



630 NEUTRAL COLOURING MATTERS. 



BERBERIN. 

This is a crystalline substance of a fine yellow colour derived by the MM. 
Buchner from the bark of barbery root, Berberis vulgaris.* The root is ex- 
hausted by means of boiling water, the decoction concentrated to the consist- 
ence of a soft extract, and this digested repeatedly in alcohol of 0.844, so long 
as the liquid acquires a bitter taste. These tinctures are filtered, a considera- 
ble portion of alcohol distilled off, and the residue left in an open vessel to 
crystallize in a cool place. It forms fine prisms of a clear yellow colour* 
without odour, but having an intensely bitter taste. It is not fusible without 
decomposition. It is sparingly soluble in cold water, largely soluble in hot 
water, soluble in alcohol, forms compounds with bases, and precipitates rea- 
dily all metallic salts. Its composition is expressed by C 33 H 1S N0 12 . Ber- 
berin answers very well as a dye stuff, and gives a fixed yellow on cotton 
cloth without any mordant. It forms also a powerful tonic. 



QUERCITRIN. 

The yellow colouring matter of quercitron bark has lately been examined 
by M. Bolley.t It was obtained from a decoction of the bark clarified by al- 
bumen, and having its tannin precipitated by isinglass, evaporated to an extract 
and treated as usual with strong alcohol. It requires about 400 parts of boiling 
water for solution, but dissolves in 4 or 5 parts of absolute alcohol. It is de- 
posited in little cauliflower-looking masses, which by a magnifying power of 
10 times are seen to be composed of small crystals. It yields by dry distilla- 
tion a yellow liquid; which soon solidifies as a clear yellow mass; this Chev- 
reul considered as unaltered quercitrin. As it restores the colour of reddened 
litmus paper, and combines with and neutralizes bases, M. Bolley considers 
it an acid and names it Quercitronic acid. The formula of the crystallized 
acid, which agrees with analysis, is HO-f-C 16 H 8 9 , of the salt of lead PbO 
-f C t 6 H 3 9 . Herm. TrommsdorfT found polychrome to have the same com- 
position, and represented it by the same formula halved.^ 



* Journal de Pharmacie, t. 17, p. 40 and t. 21, pp. 309, 408, 
t Liebig's Annalen, xxxvii, 101. X Ibid, xiv, 205, 



OXALIC ACID. 631 



CHAPTER VIII. 



ACIDS. 



SECTION I. 



ACIDS SUPPOSED TO CONTAIN CARBONIC OXIDE. 

Carbonic acid, and chlorocarbonic acid, may be considered as combinations 
of carbonic oxide, as they are formed by the union of that radical with oxygen 
and chlorine. Carbonic oxide also unites with potassium, and by the decom- 
position of this compound, croconic and rhodizonic acids are produced. 
Oxalic and mellitic acids also appear from their composition to contain the 
same radical. 



OXALIC ACID. 

Formula of the hydrated acid, HO,C 2 3 -f2HO. This acid, discovered 
by Scheele in 1776, exists in the form of an acid salt of potash, in a great 
number of plants, particularly in the species of Oxalis and Rumex; combined 
with lime it also forms a part of several lichens. Oxalate of lime occurs like- 
wise as a mineral, Humboldite, and forms the basis of a species of urinary 
calculus. This acid is also produced by the oxidation of carbon in combina- 
tion, in a variety of circumstances, being the general product of the oxidation 
of organic substances by nitric acid, hypermanganate of potash, and by fused 
potash. Those matters which contain oxygen and hydrogen in the propor- 
tion of water, furnish the largest quantity of oxalic acid. 

This acid has been derived in quantity from lichens, but it is usually pre- 
pared by acting upon 1 part of sugar, or better, starch, by 5 parts of nitric- 
acid, of 1.42, diluted with ten parts of water at a gentle heat till no gas is 
evolved, and evaporating to crystallize. The crystals must be drained, and 
crystallized a second time, as they are apt to retain a portion of nitric acid. 

It forms long, four-sided, oblique prisms, with dihedral summits, or termi- 
nated by a single face. These crystals contain three atoms of water, one of 
which is basic, and the other two constitutional, or water of crystallization. 
The latter two may be expelled at a temperature above 212°, and the proto- 
hydrate rises at the same time in vapour, and condenses as a w r oolly sublimate. 
Heated in a retort, the hydrated acid undergoes decomposition about 311°, 
and is converted into carbonic oxide, carbonic acid, and formic acid, without 
leaving any fixed residue. Nitric acid, with heat, converts oxalic acid into 



632 ACIDS DERIVED FROM CARBONIC OXIDE. 

water and carbonic acid. When heated with sulphuric acid, oxalic acid yields 
equal volumes of carbonic oxide and carbonic acid; C 2 3 being equivalent to 
CO-f-C0 2 , (page 227.) No charring, nor evolution of any other gas occurs, 
so that the action of concentrated sulphuric acid affords the means of recog- 
nising oxalic acid or any oxalate. Crystallized oxalic acid is soluble in 8 
parts of water, at 59°, in its own weight of boiling water, and in 4 parts of 
alcohol, at 59°. 

Oxalates. — With potash, and with ammonia, oxalic acid forms neutral oxa- 
lates, binoxalates, and quadroxalates. Oxalate of potash, KO,C 2 3 -f-HO, 
contains 1 atom of water of crystallization, which it loses a little above 212°; 
it crystallizes generally in prisms of six unequal sides, terminated by oblique 
dihedral summits; these crystals are soluble in 3 parts of water, insoluble in 
alcohol. Binoxalate of potash, KO,C 2 3 -fHO,C 2 3 -f 2HO, is sold under 
the name of salt of sorrel; it crystallizes in oblique, diaphanous rhomboidal 
prisms, which are soluble in 40 parts of cold water, 6 parts of hot water, and 
insoluble in alcohol. Quadroxalate of potash, KO,C 2 3 -j-HO,C 2 3 -j-2(HO, 
C 2 3 -f2HO,) crystallizes in oblique octohedrons, of which two angles are 
truncated. This salt appears to be a compound of 1 atom of binoxalate of 
potash, with 2 atoms of hydrated oxalic acid; the 4 atoms of water of crystal- 
lization, of the last mentioned constituent escape when the salt is heated to 
262°, (page 141.) Oxalate of soda, NaO,C 2 3 , is the only anhydrous alka- 
line oxalate, and is the least soluble of the salts of soda. There is also a bi- 
noxalate of soda. The oxalates of ammonia correspond in number and com- 
position with the salts of potash. The neutral oxalate of ammonia, which is 
formed by neutralizing oxalic acid with carbonate of ammonia, is much used 
as a reagent, particularly to separate lime from magnesia, and generally to pre- 
cipitate lime. It is less soluble than oxalic acid. When distilled in a glass 
retort, by a heat gradually increased, oxalate of ammonia affords a dirty white 
sublimate of oxamide, C 2 2 -fNH 2 (page 291,) together with ammonia, car- 
bonic acid, carbonic oxide, and cyanogen. 

Oxalate of lime, CaO,C 2 3 -f-2HO is thrown down as a brilliant white pre- 
cipitate, remarkable for its insolubility. It is insoluble in acetic acid, but soluble 
in nitric and hydrochloric acids. It leaves, when heated to incipient redness by 
a spirit lamp, a white residue of carbonate of lime, from which the proportion 
of oxalic acid, or of lime, may be inferred. The oxalates of magnesia, zinc, 
and manganese, have the same composition as the oxalate of lime. The first 
mentioned possesses a small degree of solubility, the others are insoluble. Oxa- 
late of copper forms a double salt with oxalate of ammonia, which corresponds 
in composition with the binoxalate of ammonia. Oxalate ofbarytes is expressed 
by BaO,C 2 3 -f HO; it is quite insoluble in water. Oxalate of silver is an 
insoluble white powder, which is anhydrous. (Phil. Trans. 1827, p. 47.) 

The double oxalates of chromium, and the aluminous class have already 
been described (pages 363, 394, and 423.) 



RHODIZONIC ACID. 

Formula of the acid supposed anhydrous : C 7 7 . Of the salt of potash, 3KO 
-f C 7 7 ; of the salt of lead 3PbO-f C 7 7 , (Thaulow.) 

This body, which derives its name from the red colour of its salts, was first 
observed by L. Gmelin, and recognised as a new acid by Heller. Potassium, 
gently heated in carbonic oxide, absorbs that gas with avidity, fusing of a green 
tint, and spreading over the sides of the vessel ; afterwards the oxicarburet 
becomes black and porous. Allowed to cool, it is dissolved with water, when 
a violent disengagement of combustible gases occurs, and a red solution is 



MELLITIC ACID. 633 

formed, containing rhodizonate of potash. The same oxicarburet of potassium 
is formed in large quantity, as an accidental product in the preparation of potas- 
sium from carbonate of potash and charcoal, being found as a black mass in the 
neck of the retort, or in the receiver with the potassium. The salt from the 
oxicarburet may be deprived of the excess of caustic potash by alcohol, in which 
the rhodizonate of potash is insoluble. 

Rhodizonic acid is apt to undergo decomposition in being liberated from its 
salts, and has not been obtained in a state of purity. All its salts are red, and 
in the dry state have a metallic lustre, and reflect green. Its potash salt under- 
goes a remarkable decomposition when its solution is heated, being converted 
into free potash, oxalate of potash, and croconate of potash: . 

3KO-f C 7 7 =KO and KO-j-C 2 3 and KO+C 5 4 . 



CROCONIC ACID. 

Formula of the acid supposed anhydrous, C s 4 . 

This acid derives its name from the saffron-colour of its salts ; it was dis- 
covered by L. Gmelin. The croconate of potash is deposited in long yellow 
and brilliant needles from a solution of rhodizonate of potash, which has been 
decomposed by ebullition. The acid may be obtained free, by decomposing 
croconate of potash by hydrofluosilicic acid, and evaporating to dryness. It is 
strongly acid, crystallizes of a yellow colour easily, and is soluble in alcohol. 

Croconate of potash, K0,C 5 4 -f 2HO, crystallizes in long orange prisms of 
6 or 8 sides, having a nitrous taste ; loses its 2 atoms of water at a moderate 
heat and becomes lemon yellow. It is insoluble in alcohol, in common with 
all the salts of this acid except the croconate of ammonia which is soluble in al- 
cohol. 

Croconate of lead, PbO,C 5 4 +HO, precipitates in golden yellow micaceous 
plates, when a hot and dilute solution of acetate of lead is added to a solution of 
croconate of potash containing acetic acid. 

Hydrated croconic acid has been considered as a hydracid H-|-C 5 5 ,that is, 
a compound of hydrogen, and a salt-radical ; a constitution which is analogous, 
being assigned to mellitic acid. 

The gas evolved when oxicarburet of potassium is dissolved in water is not 
pure hydrogen, but contains carbon, and is distinguished, according to Mr. E. 
Davy, from all the other carburets of hydrogen, by the property it possesses of 
inflaming at the ordinary temperature and depositing carbon, when mixed with 
an equal volume of chlorine. 



MELLITIC ACID. 

Formula of the crystallized acid: H,C 4 4 , or HO-f C 4 3 of the mellitates 
dried at 212°, M,C 4 4 +H0, or MO,C 4 3 +HO. 

This acid was discovered by Klaproth in a rare mineral, ?nellite, which is the 
mellitate of allumina. The free acid is best obtained, according to Wcehler, by 
decomposing the mellitate of lead by sulphuretted hydrogen ; it is a white crys- 
talline powder, soluble in water and alcohol ; from the last of which it crystal- 
lizes by slow evaporation in needles radiating from a centre. The dry acid is 
not altered by a temperature of 572° (300° centig.,) nor is it decomposed by 
boiling nitric or sulphuric acid. 

Mellitates. — Potash soda and ammonia form acid besides neutral mellitates. 
Nitrate of potash forms a remarkable double salt with bimellitate of potash 



634 MECONIC ACID. 

KO,NO^-f 4(HO,M-f KO,M)-f 6HO, described by Woehler. It is remarkable 
that the nitrates particularly give rise to combinations in such proportions. 
Neutral mellitate of ammonia undergoes a remarkable decomposition by heat, 
which has been lately investigated by Woehler. Heated for some time be- 
tween 302° and 320°, it loses ammonia, and is transformed into a pale yellow 
powder, which water decomposes into two substances, one of which, paramide, 
is white and insoluble and the other a soluble ammoniacal salt, of which the acid 
is named euchronic (from £v%poor, of a fine colour.) The composition of paramide 
is C 8 HN0 4 ; it appears to be formed from 2 atoms of mellitate of ammonia, 
C 8 H 8 N 2 8 , by the loss of 1 atom of ammonia and 4 atoms of water. By boil- 
ing with water, particularly under pressure at 392° (200° centig.,) it is converted 
into acid mellitate of ammonia. 

* Euchronic acid, 2HO,C 12 NO fi +2HO, is separated from the above acid 
ammoniacal salt by nitric or hydrochloric acid. It crystallizes in very small, 
colourless, rhomboidal prisms, which have a strong acid taste, and dissolve with 
difficulty ; they lose 2HO at 392°. It fuses and is decomposed above 536°. 
When crystallized euchronic acid is heated to 392°, in a glass tube hermetically 
sealed, with a quantity of water insufficient to dissolve it, a complete solution is 
obtained, in which, however, the euchronic acid is converted into acid mellitate 
of ammonia. Euchronic acid is distinguished from all other organic compounds 
by the way in which it comports itself with metallic zinc. A slip of zinc dipped 
in a solution of this acid, immediately becomes of a magnificent blue colour at 
its surface ; this colour becomes at the boiling point nearly as intense as that of 
indigo. Washed and dried, it forms a black mass which contains no zinc. 
When slightly heated, even upon paper, it becomes immediately completely 
white, and is changed anew into euchronic acid. M. Woehler applies the name 
euchrone to the blue compound, and considers that the action of zinc in its 
formation is a deoxidating one, euchrone being an inferior degree of oxidation 
of the radical of euchronic acid, or that radical itself; but from want of material 
this singular and most interesting body was not fully investigated. (Ann. de 
Chim. &c. 3 ser. ii, 78.) 

Mellitate of silver undergoes a particular decomposition at 356°, losing an 
atom of water, and becoming Ag,C 4 4 . 

Mellitate of allumina, native mellite or honeystone, is composed of A1 2 3 , 
3C 4 JH.-T- 18HO, according to Woehler. It crystallizes in regular octahedrons, 
of a honey-yellow colour; is insoluble in cold water, and decomposed by boil- 
ing water. 



SECTION II. 



MECONIC ACID AND ITS CONGENERS. 

Meconic acid, 3HO,C 14 HO tl -f6HO, is a tribasic acid, which crystallizes 
with 6 atoms of water of crystallization. It is found only in opium, of which 
it is the characteristic acid; it is named from pcwm, the poppy. It is best ob- 
tained by decomposing meconate of potash dissolved in 16 to 20 parts of hot 
water with 2 or 3 parts of pure hydrochloric acid, and crystallizes on cooling. 
The solutions in this process must neither be boiled, nor filtered through paper, 
as the latter may contain iron. (Robiquet.) It crystallizes in pearly plates, 
which are soft to the touch, and possess an acid and astringent taste. It is 
sparingly soluble in cold water, but very soluble in hot water ; it is equally 
soluble in alcohol. Salts of the peroxide of iron produce a deep red solution 



TANNIC ACID. 635 

with meconic acid, without occasioning any precipitate. Chloride of mercury- 
does not destroy the colour of this solution (Parnell,) a property by which me- 
conic acid may be distinguished from the persulphocyanide of iron, which is 
also red, but becomes yellow when chloride of mercury or gold is added to it. 

A concentrated solution of meconic acid becomes yellow, when boiled, and 
then deep brown, and there are formed carbonic acid, oxalic acid, comenic 
acid, and a dark brown matter. Boiling dilute sulphuric acid, or hydrochloric 
acid, converts it with effervescence into carbonic acid and comenic acid. 

The meconates contain all 3 atoms of base, one of which is generally water. 
Meconate of lead contains 2 atoms of oxide of lead ; it is an insoluble white 
powder, which is thrown down from a solution of opium by acetate or subacetate 
of lead. After being washed, it is diffused through water and decomposed by 
a stream of sulphuretted hydrogen, to liberate the meconic acid, which may 
then be indicated by a persalt of iron; becoming of a wine-red colour. 

Comenic acid, 2HO,C 12 H 2 O s , a bibasic acid, which crystallizes in very hard 
crusts or crystalline grains, with nothing more than its basic water. It is 
formed, as already stated, on boiling a solution of meconic acid with a pretty 
strong acid ; also by heating dry meconic acid to 392°, when carbonic acid is 
disengaged till the temperature rises to 446°, when the meconic acid is found 
to be entirely converted into comenic acid. In this transformation, the former 
hydrated acid loses 2 atoms of water and 2 atoms of carbonic acid: C 14 H 4 
O 14 =C 12 H 2 8 and H 2 2 and C 2 4 . 

Comenic acid dissolves in 16 parts of boiling water; its solution decomposes 
the alkaline carbonates, and reddens salts of peroxide of iron. At 572°, it is 
decomposed and resolved into water, carbonic acid and pyromeconic acid. 
The comenates contain all two atoms of base, one of which is occasionally 
water. 

Pyromeconic acid, HO,C 10 H 3 O 5 , a monobasic acid, which presents itself as 
a colourless sublimate, composed of brilliant flattened plates, when crystallized 
comenic acid is submitted to dry distillation: C, 2 H 4 O 10 =C 10 H 3 O 5 and HO 
and C 2 4 . Its taste is styptic, with a bitter after-taste ; it fuses between 248° and 
2,57° into an oily liquid, and sublimes without leaving any residue. It is very 
soluble both in water and alcohol. It reduces a solution of gold, and communi- 
cates a red colour to solutions of peroxide of iron. Its salt of lead is a white 
precipitate, of the composition, PbO,C 10 H 3 O 5k 



SECTION III. 



TANNIC ACID AND BODIES ALLIED TO IT. 

The formula of tannic acid or tannin dried at 212° is 3H04-CJ 8 H 5 9 : it is 
a tribasic acid. 

Tannic acid occurs in the bark of all the varieties of Q,uercus and many 
other trees, and in gall-nuts, from which it is procured in greatest purity. It is 
prepared, after Pelouze, in a percolator or apparatus of displacement, fig. 127, 
the lower opening of which is closed by a plug of cotton, and the vessel entirely 
filled with broken gall-nuts, which are more suitable for the experiment than 
the powder of gall-nuts. Over the gall-nuts as much aqueous ether is poured 
as the vessel will contain, and the mixture left to digest for several hours. The 
liquid is then permitted to run off into the caraffe below, by loosening the stopper 
above and admitting air. It is found to divide into two liquids, of which the 



636 



TANNIC ACID AND BODIES ALLIED TO IT. 



Fig. 127. denser syrupy and yellowish one, is a very concentrated solution of 
tannic acid in water, and the lighter, which is coloured green, an 
ethereal solution of gallic acid and other matters. Additions of ether 
are made to the gall-nuts, so long as two different liquids flow from 
the lower orifice. The aqueous ether employed is obtained by 
agitating common ether with water. If the gall-nuts be moistened 
with water before the addition of the ether, the solution of tannin 
which comes off is highly coloured ; but if the gall-nuts be merely 
exposed to steam, and washed in the percolator with anhydrous 
ether, the process succeeds equally well as with the aqueous ether. 

By the evaporation of the solution of tannin, a yellow light mass 
is generally obtained, which is purified by solution in water, and 
evaporation in vacuo over sulphuric acid. It then forms a mass 
colourless or slightly yellow, which is not crystalline but resembles 
dried gum, and becomes somewhat deeper in tint in humid air, but 
is not otherwise altered. It is dissolved easily by water and in 
large quantity; the taste of the solution is purely astringent with- 
out bitterness, it reddens vegetable blues, and decomposes alkaline 
carbonates with effervescence. Tannic acid is soluble in aqueous 
alcohol, but only very slightly soluble in ether. Its solution is 
affected by air, particularly at a high temperature, oxygen being 
absorbed and an equal volume of carbonic acid evolved, while 
the tannic acid is transformed into gallic and ellagic. acids. But the so- 
lution of tannic acid keeps without change in close vessels. A mode- 
rately strong solution of tannic acid gives with sulphuric, hydrochloric, 
phosphoric, arsenic or boracic acid, a thick white precipitate, which is a com- 
pound of the two acids mixed, and is very soluble in pure water and in 
alcohol. When the solution of tannic acid is precipitated hot by sulphuric 
acid, a resinous mass is formed, which dissolves in dilute sulphuric acid at 
the point of ebullition, of a deep tint, and after being boiled for some minutes is 
converted, without any evolution, of gas, into gallic acid, which crystallizes on 
the cooling of the solution. Tannic acid boiled in an excess of caustic alkali, 
undergoes the same transformation. 

Tannic acid precipitates animal gelatine entirely from solution in thick 
flocks, which adhere and form a viscid elastic mass when the acid is in excess; 
this precipitate dissolves in the supernatant liquid at the boiling point. It is 
known as tanno gelatin, and contains about half its weight of tannin. Tannin 
is also absorbed from solution by the fresh skin of animals, which is then 
tanned or converted into leather, and ceases to be soluble in water or to be 
putrescible. Tannic acid also precipitates a solution of starch and of albumen, 
and is capable of combining with animal fibrin. 

Tannates. — The neutral tannate of potash or ammonia appears as a thick 
precipitate, when a moderately dilute solution of tannic acid is treated with 
that alkali or its carbonate; the precipitate is very soluble in an excess of 
alkali. Tannates of barytes, strontian, lime, and magnesia are very sparingly 
soluble. Salts of protoxide of iron undergo no alteration when mixed with a 
solution of tannic acid, but if exposed to air become soon of a deep bluish- 
black colour. Tannate of peroxide of iron is a black pulverulent precipitate, 
Fe 2 3 ,C 1 8 H 5 9 -f 9HO (Pelouze,) formed on adding persulphate of iron to 
a solution of tannic acid; it is the basis of writing ink. A good black ink is 
prepared from bruised Alleppo galls 6 ounces, copperas (sulphate of iron) 4 
ounces, gum arabic 4 ounces, water 6 pints. The galls are boiled in the 
water, the other ingredients then added, and the whole kept in a wooden 
or glass vessel and occasionally shaken. In two months strain, and pour 
off the ink into glass bottles to be well corked. To prevent mould, add 



GALLIC ACID. 637 

one grain of corrosive sublimate or three drops of creosote to each pint of 
ink. (Brande's Manual, p. 1105.) Tartar emetic gives a white precipi- 
tate with tannic acid, the tannate of antimony, Sb0 3 -f 3C 1 8 H 5 9 . Tannic 
acid forms sparingly soluble white precipitates with most of the organic 
bases. 

GALLIC ACID. 

Formula of the crystallized acid, 2HO,C 7 H0 3 -fHO; of the acid dried at 
212°; 2HO,C 7 H0 3 . Of one gallate of lead dried at 212°; HO,PbO,2C.H0 3 
-f HO; the last atom of water is lost at 320°. Of another gallate of lead: 
2PbO,C 7 H0 3 . Of acid gallate of ammonia, the composition is expressed bv 
NH 4 0,C 7 H0 3 -f2HO,C 7 H0 3 ; itloses nothing at 212°. These are the only 
sails of gallic acid of which the composition is certainly known, and they are 
not sufficient to determine whether or not gallic acid is bibasic. 

The metamorphosis of tannic acid into gallic acid, under the influence of 
boiling dilute sulphuric acid has already been adverted to. The same change 
occurs in an aqueous extract of gallnuts exposed to air for several months. By 
the absorption of 8 atoms of oxygen, 1 atom of hydrated tannic acid might be 
converted into 2 atoms of hydrated gallic acid, 4 atoms of carbonic acid, and 2 
atoms of water: C 18 H 8 12 and 8 =2C 7 H 3 5 and 4C0 2 and 2HO. Much 
ellagic acid is also formed in the transformation of the tannin of gallnuts, in the 
air. To prepare gallic acid, a strong extract of gallnuts in cold water may be 
precipitated in the cold by sulphuric acid ; the thick mass be mixed with dilute 
sulphuric acid, expressed while still humid, and introduced in this state into a 
mixture of sulphuric acid with two parts of water at the boiling temperature. 
The liquid is boiled for some minutes and then allowed to cool; crystals 
of gallic acid are deposited which may be purified by crystallizing again 
from water, converting the new product, which is still coloured by means 
of acetate of lead into an insoluble gallate of lead, which last is washed, then 
diffused through water, and decomposed by a stream of sulphuretted hydro- 
gen gas; the sulphuret of lead, which is then formed, assists in carrying down 
the colouring matter. 

Gallic acid crystallizes on cooling from a hot solution, in thin, silky needles. 
It requires 100 parts of cold water to dissolve it, but is soluble in 3 parts of 
boiling water. It is also very soluble in alcohol, and to a small extent in ether. 
When pure it does not precipitate a solution of gelatine. The aqueous solution 
of this acid may be kept apart from air without change, but with access of ox- 
ygen it undergoes decomposition, a brown matter being deposited, while car- 
bonic acid is evolved and the surface becomes covered with mouldiness. This 
decomposition is greatly promoted by the presence of a mineral acid, or of an 
alkali in the solution. With salts of peroxide of iron gallic acid assumes a deep 
blue tint; the black precipitate which falls, left in contact with gallic acid, is 
gradually reduced to the state of protoxide, but not when a salt of the ferroso- 
ferric oxide has been employed in its formation. 

When crystallized gallic acid is dissolved in concentrated sulphuric acid, and 
the solution heated, it assumes a crimson tint at a temperature above 284°. If 
allowed to cool in this state, and cold water afterwards added, an abundant 
precipitate is formed of a reddish brown colour and crystalline aspect, which 
appears to be gallic acid that has lost an atom of water, its composition after 
drying being C 7 H 2 4 (Robiquet.) It is insoluble in water, but dissolves easily 
in alkalies, and has some analogy, according to Robiquet, to the colouring mat- 
ter of madder, it is decomposed by dry distillation, giving small cinnabar-red 
prismatic crystals. 

All the gallates are remarkable for the facility with which they absorb oxygen, 
54 



638 TANNIC ACID AND BODIES ALLIED TO IT. 

when in contact with an excess of alkali ; carbonic acid is then formed and a 
brown matter insoluble in water. In a mineral water alkaline from the pre- 
sence of lime or magnesia, an addition of gallic acid causes the liquid gradually 
to become turbid from the formation of a black precipitate, although no iron be 
present, owing to the decomposition of the gallic acid itself 

Pyro gallic acid C 6 H 3 3 ,orC 8 H 4 4 (the equivalent being doubtful,) is pre- 
pared by heating briskly either tannic or gallic acid, previously well dried, in a 
retort by means of a spirit-lamp till coloured empyreumatic products come over. 
The pyrogallic acid is obtained as a crystalline sublimate, which may be puri- 
fied by a second sublimation at a gentle heat. It forms white plates or needles, 
fuses at 239°, boils at 410°, and sublimes without alteration. It does not red- 
den litmus ; its taste is bitter and slightly astringent. It dissolves in 21 parts of 
water at 55°.4 (13° centig. ;) the solution absorbs oxygen and deposits a brown 
powder. It is equally soluble in alcohol and ether. When heated briskly 
above 482° (250° centig.,) pyrogallic acid blackens, and is converted into water 
end metagallic acid. 

Pyrogallate of had, a white precipitate formed on adding a solution of py- 
rogallic acid to acetate of lead, is PbO,C 6 H 3 3 , according to Berzelius, and 
also Pelouze, but PbO,C 8 H 4 4 according to the later analysis of R. C. Camp- 
bell. 

Metagallic acid, melangallic acid (Berzelius.) The formula of the anhy- 
drous acid is C 6 H 2 2 (Pelouze;) its probable atomic weight: HO,C 12 H 3 3 . 
This body remains as a fixed residue in the retort when gallic acid or tannic 
acid is heated by an oil bath to 482°, till all the volatile products escape. It 
is then dissolved in a solution of alkali and precipitated by an acid to obtain it 
in a state of purity. It is a black powder, insoluble in water, which forms 
soluble compounds with alkalies of a deep black colour. 

Tannic and gallic acids, although differing so much in composition, afford 
the same products when decomposed by heat. This is explained by sup- 
posing tannic acid a compound of gallic and pyrogallic acids. In fact 3 atoms 
of tannic acid contain the elements of 6 atoms of gallic acid, and 2 atoms of 
pyrogallic acid. 

3(C 1 ,H,0„)-6(C 7 H 1 0,)+2(C,H,0 J .) 

Ellagic acid. — The gallic acid which forms in an infusion of gailnuts ex- 
posed to air, is always accompanied by a gray powder, which being insoluble, 
may be purified by boiling water; it is the acid in question. Ellagic acid dis- 
solves in alkalies and is precipitated by acids. According to Pelouze it pos- 
sesses the same composition as dried gallic acid, C 7 H 3 0j; between 212° and 
248°, it loses an atom of water and becomes C 7 H 2 4 . 

Catechu, the brown dried extract of the Acacia or Mimosa catechu contains 
a large quantity of tannic acid differing little from the 'tannic acid of gallnuts, 
which may be extracted by cold water. The portion insoluble in cold water, 
contains a particular principle catechin, C ]5 H 6 6 (Swanberg.) Two acids 
are produced when catechin with alkalies or alkaline carbonates absorbs 
oxygen from the air, and forms black solutions with the former and red with 
the latter; which have been named japonic mid, HO-f-C, 2 H 4 4 , and rubinic 
acid, HO,C 18 H 6 9 (Swanberg.) 



CITRIC ACID. 639 



SECTION IV. 



CITRIC ACID AND THE PRODUCTS OF ITS DECOMPOSITION. 

Formula of citrate of silver, 3AgO + Cj 2 H 5 1V Of the crystals of citric 
acid formed on the cooling of a solution saturated at 212°, 3HO,C 12 H 5 11 
-f-HO, which may be named hydrate A; this hydrate loses no weight and 
preserves its transparency at 212°. It is the type upon which most of the 
citrates are formed. Of the crystals formed by the spontaneous evaporation 
of a solution saturated in the cold, the formula is 3HO,C l2 H 5 1 1 -f2HO; of 
which the two atoms of water of crystallization are lost at 212°. 

Citric acid was discovered by Scheele; it exists in a considerable variety of 
plants, but is procured only in quantity from the orange and lemon and from 
gooseberries. The acid juice of these fruits is neutralized by a known weight 
of carbonate of lime; the insoluble citrate of lime washed, and then decom- 
posed by a quantity of oil of vitriol equal in weight to the carbonate of lime 
used, diluted with 5 parts of water. The acid liquid is separated by filtration 
from the insoluble sulphate of lime; and the citric acid crystallized with a 
slight excess of sulphuric acid present, which is observed to favour the crys- 
tallization, while it is impeded by citrate of lime in solution. 

Citric acid crystallizes in regular rhomboidal prisms, 
(fig. 128) terminated by four faces, has an agreeable acid Fig. 128 . 

taste, and is soluble in an equal weight of water forming 
a thick syrup. A dilute solution of citric acid in water 
does not keep, but becomes covered with mouldiness. 
When pure, citric acid dissolves completely in alcohol, 
without residue, and does not give a precipitate with lime- 
water. But when a few drops of the acid are added to 
the latter in excess, the clear liquid obtained becomes tur- 
bid when heated, from the deposition of a white basic 
citrate of lime, 3080,0, 2 H 5 0, , -fCaOJIO, which dissolves in acids with- 
out effervescence. Citric acid is commonly distinguished by that property. 
Hydrate A of citric acid, which contains 4 atoms of water fuses at 266°, and 
loses nothing, although hydrate B, which contains 5H0, loses 2H0 at 212°. 
When the temperature of 302° is exceeded the acid of both hydrates under- 
goes decomposition. When 1 part of crystallized citric acid is gently heated 
with 4 parts of oil of vitriol, a considerable quantity of carbonic oxide is 
evolved, and acetic acid is formed. When fused with an excess of hydrate 
of potash, citric acid is decomposed into oxalic and acetic acids; 1 atom of 
citric acid containing the elements of 2 atoms of acetic acid, 2 atoms of oxalic 
acid and 2 atoms of water. 

Citrates. — The neutral salts of citric aeid, besides 3 atoms of fixed base, 
carry along with them the atom of water of acid hydrate A; which water how- 
ever they either abandon at the ordinary temperature, like the citrate of silver. 
or at a high temperature. In certain subcitrates this atom of water is replaced 
by an atom of metallic oxide, such as lime or oxide of lead. The composition 
of these salts has received considerable attention. The following are the formulae 
of the most remarkable citrates: 

Citrates of potash: three salts exist containing as base respectively, 3K0 ; 




640 ORGANIC ACIDS. 

2KO-f-HO;andKO+2HO. Citrates of. so da: salt .tf,3NaO,C 12 H 5 O n + 11 HO 
(Berzelius;) loses 7HO at 212°, and the remaining 4HO between 374° and 
392° (190° and 200° centig.) Salt B, 2NaO,HO,C 12 H 5 11 . Salt C, NaO, 
2HO,C 12 H 5 11 . Citrate of barytes, 3 BaCC^H^O^+ZHO (Berzelius;) 
loses 6HO at 302° and becomes anhydrous at 374 c . Another citrate of barytes 
appears to be a compound of the preceding salt, with 2BaO,HO,C 12 H 5 O i:i , its 
empyrical formula being 2C 19 H 5 O n -f 5BaO-}-8HO. Citrate of lime, 3CaO, 
C 2l U s 11 +4HO (Berzelius;) it loses 3HO at 212°, and the remaining HO 
at a higher temperature. The subcitrate of lime lately mentioned loses HO at 
212°. Citrates of lead: salt A, SPbO.C^H^n+HO. Salt B, 2PbO.HO. 
c i2 H 5 11 +2HO. Salt C, 3PbO,C 12 H 5 11 +3PbO. SaltD, 3PbO,C 12 H 5 
O^+PbO.HO. Citrate of copper, 3Cu0,C lo H s 11 + CuO. Citrate of silver, 
SAgO^^HjO^+HO; loses HO between 68° and 77°. Citrate of antimony 
and potash, Sb0 3 ,C 12 H s 11 -f-3KO,C 12 H ? 11 +-5HO (Thaulow;) it crys- 
tallizes in prisms of a brilliant whiteness which lose their whole water of crys- 
tallization at 212°. Citrate of e%/3EO,C 12 H 5 O ir (Liebig's Traite, ii, 45.) 

Aconitic acid, HO-r-C 4 H 2 3 . — When crystallized citric acid is heated, it 
fuses, gives off water, but undergoes no essential change till inflammable gases 
are disengaged, and afterwards an acid liquid which condenses in oily striae. 
with carbonic acid gas. These appearances indicate two stages in the dis- 
tillation, and if the process be interrupted when the disengagement of water 
and inflammable vapour ceases, the fixed residue in the retort contains no citric 
acid, but a new acid produced by its decomposition, which proves to be the 
same with the acid from the Aconitum napellus and Eqidsetumjluviatile, and 
which was already known under the names of aconitic and equisetic acid. 
This acid is soluble in ether, which citric acid is not. It is also readily con- 
verted into aconitic ether, by the action of dry hydrochloric acid upon its so- 
lution in alcohol, and is precipitated by water, while citric acid not being etheri- 
fied by this process remains in the liquor. Aconitic ether is easily decomposed 
by caustic potash, and the acid may be derived from the potash salt. Aconitic 
acid forms only small confused crystals. When briskly distilled it affords the 
two following isomeric acids, which sublime (see page 487.) 

Jtaconic acid, HO-fC 5 H 2 3 ; known also as pyrocitric acid and citricic 
acid. It crystallizes in rhomboidal tables, is soluble in 17 parts of water at 50°, 
in 10 at 68°; soluble also in alcohol and ether. 

Citraconic acid (hydrated,) HO-f C 5 H o 3 ; distinguished also as citribic acid 
by M. Baup. It is obtained anhydrous by distillation as an oily limpid liquid, 
C 5 H 2 3 , which distils at £12° without decomposition. 



SECTION V. 



TARTARIC AND PARATARTARIC ACIDS AND THE PRODUCTS OF 
THEIR DECOMPOSITION. 



TARTARIC ACID. 

Formula of the crystallized acid, 2HO-f C 8 H 4 O l0 ; a bibasic acid. 

This acid, which in common with so many others was first prepared by 



TARTARIC ACID. 641 

Scheele, exists in many fruits, and also as tartrate of lime in several roots, but is 
prepared only from the juice of the grape, which contains tartaric acid in the form 
of tartar or bitartrate of potash. The last salt precipitates during the fermen- 
tation of wine, owing to its insolubility in alcohol ; in the crude state, it is known 
as argol, and is highly coloured, when purified, as cream of tartar. To procure 
tartaric acid, cream of tartar is dissolved in boiling water and neutralized with 
carbonate of lime, which throws down one-half of the tartaric acid as an insoluble 
tartrate of lime ; the other half of the acid contained in the neutral tartrate of 
potash, is precipitated by a solution of chloride of calcium. The tartrate of 
lime is decomposed by an equivalent quantity of sulphuric acid, and the tartaric 
acid separated from the insoluble sulphate of lime by filtration; 3 parts of oil of 
vitriol are usually taken for 5 parts of cream of tartar. The acid solution is 
evaporated in leaden vessels by a gentle heat, during which process some sul- 
phate of lime is deposited. A syrupy solution of tartaric acid left in a warm 
place yields crystals which are oblique prisms of a rhombic base, terminated by 

Fig. 129. Fig. 130. 





dihedral summits and truncated on the longitudinal edges, or hexagonal prisms 
terminated by three faces of truncation ; but the two parallel faces are generally 
more developed than the others, so as to give the crystals the appearance of 
tables. The crystals are persistent in air, of a strongly acid and agreeable 
taste, dissolve in 1 h, parts of cold water and in less hot water, and are equally 
soluble in alcohol. The aqueous solution of tartaric acid and its salts undergoes 
decomposition, and becomes covered with mouldiness. When the crystallized 
acid is heated, it loses water and produces a series of new compounds. Treated 
at a high temperature with a strong solution of hydrate of potash, tartaric acid 
is entirely converted into acetate and oxalate of potash ; one atom of crystallized 
tartaric acid actually containing the elements of 1 atom of hydrated acetic acid 
and two atoms of hydrated oxalic acid: 

2HO+C 8 H 4 O 10 =HO,C 4 H 3 O 3 and 2(HO,C 2 3 .) 

A solution of tartaric acid does not disturb solutions of chloride of barium 
and chloride of calcium, but produces a white precipitate in barytes and lime- 
water, and in acetate of lead. A solution of tartaric acid is also used in pre- 
cipitating potash from its salts, when not very dilute, the bitartrate of potash 
falling down, upon agitation, as a granular precipitate, which is sparingly soluble 
in water, but ^dissolves readily in hydrochloric acid. The addition of tartaric 
acid to many metallic solutions, prevents their precipitation by alkalies. 

Tartrates. — According as one or both atoms of water in tartaric acid are 
replaced by a metallic oxide, an acid or neutral tartrate is formed, and when 
the 2 atoms of metallic oxide are different, a double tartrate. 

Neutral tartrate of potash, 2KO,C s U^O 10 is anhydrous, and soluble in an 

54* 



642 



ORGANIC ACIDS. 



equal weight of cold water.* Acid tartrate of potash (bitartrate,) HO.KO,C 8 
H 4 O 10 is also anhydrous, soluble in 18 parts of boiling water, and in 184 parts 
of water at 08° ; it is insoluble in alcohol, f Purified tartar, when heated alone, 
gives a carbonaceous mixture (black flux,) and when deflagrated with 2 parts 
of nitre, it leaves white carbonate of potash (white flux.) Tartrate of potash 
and soda, or rochelle salt, KO.NaO,C 8 H 4 O 10 -J-iOHO (Schulze,) is formed by 
neutralizing acid tartrate of potash with carbonate of soda, is soluble in half its 
weight of cold water and persistent in air.J It crystallizes with two equivalents 
of the tartrate of potash and boracic acid, and forms a double salt, which is 
anhydrous. Neutral tartrate of ammonia, 2NH 4 O,C 8 H 4 O 10 -f2HO (Dulk.) 
Acid tartrate of ammonia resembles acid tartrate of potash. A hot solution of 
this salt dissolves a large quantity of arsenious acid, and yields, by evaporation, 
large and transparent crystals of a salt of two bases, NH 4 O,AsO 3 ,C 8 H 4 O 10 , 
analogous in composition to tartrate of potash and antimony. Tartrate of 
potash and boracic acid, KO.BO 3 ,C 8 H 4 O 10 (Duflos,) is a white uncrystalline 
mass, very soluble in water, obtained by dissolving a mixture of 47 & parts of 
cream of tartar (1 atom,) and 15^ parts of crystallized boracic acid (1 atom,) 
by means of hot water. Heated in a dry condition to 482° (250° centig.,) this salt 
loses 2HO, like tartrate of antimony and potash, at the expense of the elements of 
the acid, the empyrical formula of the salt becoming C 8 H 2 8 ,KO,B0 3 (Soubeiran 
and Capitaine.) Tartrate of potash and peroxide of iron (page 394,) is a phar- 
maceutical preparation; its composition when dried at 212° is KO.Fe 2 3 ,C 8 H 4 
0, , (S. and C.) Tartrate of antimony is a salt, crystallizing with difficulty, of 
which the composition is unknown. Three double tartrates of antimony and 
potash are known: (1.) Tartar emetic (page 441,) the formula of which, dried 
at 212°, is KO.SbO 3 ,C 8 H 4 O 10 , and heated to 392° (200° centig.,) KO.Sb0 3 C 8 
H 2 8 . (2.) Tartar emetic combines with 3 atoms of the acid tartrate of pot- 
ash, and forms a crystallizable double salt, when the mixture of these two salts 
is kept constantly boiling in the preparation of tartar emetic (Knapp.) (3.) A 
salt KO.SbO^Cgl^Oj -f 7HO (Knapp,) formed by dissolving together 9 parts 
of tartar emetic, and 4 parts of crystallized tartaric acid, which is very soluble 



by-means of cream of tartar. The excess of acid combines with potassa to form the neutral 
tartrate. Tartrate of potassa crystallizes generally in irregular hexagonal prisms, derived 
from the right rhombic prism, (fig. 131,) which are slightly deliquescent and with a bitter 
saline taste. R. B.] 

[t Acid tartrate of potassa is deposited in an impure state on the inside of wine casks^ 
constituting crude tartar or argol. Argol is purified by solution in hot water from which 
the acid tartrate crystallizes on cooling in white crystalline crust. The crystals are hard, 
gritty and but slowly soluble in water, with a slightly acid taste. R. B.] 

[t Tartrate of soda and potassa forms large and transparent crystals, (fig. 132 and 133,} 



Fig. 131, 



Fig. 132. 



Fig. 133. 




jjSL 


1? 


~\ 


<s 


71 M 


y 


f 9 


M. 


\ 




— 







/ 


h 


/,-\ 


/ 

i 




sS. 


P 


! 




ff 


{/ 



belonging to right rhombic prisms, but frequently split longitudinally through their axis. 
Their taste is saline and bitter, soluble in two and a half parts of cold water and slightly 
efflorescent. R. B.] 



ACTION OF HEAT UPON TARTARIC ACID. 643 

and crystallizable. Tartrate of antimony and lead, PbO,Sb0 3 ,C 8 H 4 0j (Du- 
mas,) the white precipitate which falls on adding a salt of lead to a solution of 
tartar emetic, dried at 212°. Heated to 392°, it loses 2HO, like tartar emetic. 
Action of heat upon tartaric acid. — Tartaric acid fuses between 266° and 
284°, and becomes brown at 320°. By the action of heat it loses first one 
fourth, then one half, and finally the whole of the water of its hydrate (Fremy,) 
forming two new acids, the relation of which to tartaric will be best seen 
by doubling the formula of the latter: 



Anhydrous tartaric acid . . C 1fi H Q 
Tart relic acid . 
Tartralic acid . 
Crystallized tartaric acid . 



C l6 H 8 O 30 + 2HO 

C 16 H 8 O 20 3HO 

C 1G H 8 20 +4HO 



When the solutions of the modified acids are boiled, they are quickly eon- 
verted into ordinary tartaric acid.* Representing anhydrous tartaric acid by 
C 4 H 2 5 , we have then, for the modified acids, the following formulae (Lie- 
bigO 

2(C 4 H 2 5 )-j-2HO . . crystallized tartaric acid. 
3(C 4 H 2 5 )+2HO . . tartralic acid. 
4(C 4 H 2 5 )-f-2HO . . tartrelic acid. 

The salts of tartralic and tartrelic acids with alkaline bases are not crystal- 
lizable. Anhydrous tartaric acid is produced by keeping the crystallized tar- 
taric acid for some time in an oil bath, at 302° (150° centig.;) it is insoluble 
in cold water. 

Tartaric acid yields the two following acids by its destructive distillation: 

Liquid pyrotarlaric acid, HO,C 6 H 3 5 , which forms a monobasic ether 
and other salts. 

Solid pyrotarlraric acid, HO,C 5 H 3 3 (Pelouze,) is formed only in small 
quantity by the distillation of tartaric acid, but in larger quantity by the dis- 
tillation of acid tartrate of potash (Weniselos.) 



PARATARTARIC (RACEMIC) ACID. 



Liebig assigns to this acid, dried at 212°, the formula HO -f-C 4 H 2 5 , which 
contains half the number of atoms in tartaric acid, and considers the former as 
a monobasic acid, while tartaric acid is bibasic. By this difference, the iso- 
merism of these two acids (page 129,) is accounted for. Crystallized para- 
tartaric acid contains an additional atom of water, and is represented bv HO, 
4 H 2 5 +HO. 

Paratartaric acid was discovered by Mr. Kestner, of Thann, and particu- 
larly studied by John, by Gay-Lussac and Berzelius. It forms no double 
salt of potash and soda, analogous to Rochelle salt, and is probably on that 
account monobasic. Paratartaric acid is contained in the cream of tartar of 
the wines of the Vosges, and perhaps other localities, and is separated by 
neutralizing that salt with corbonate of soda, and crystallizing out the tartrate 
of potash and soda. The mother liquor is precipitated by chloride of calcium, 

* Fremy ; Ann. d: Chim. ct de Phys. t. 68, p. 353. 



644 ORGANIC ACIDS. 

and the mixed tartrate and paratartrate of lime decomposed by sulphuric acid; 
on concentrating the paratartaric acid crystallizes before the tartaric, being 
considerably less soluble. 

Paratartaric acid crystallizes in oblique prisms, of a rhombic base, which 
effloresce in dry air. It is a more powerful acid than tartaric, decomposing 
nitrate and sulphate of lime and chloride of calcium, with precipitation of 
paratartrate of lime. Hence paratartaric acid was first mistaken for oxalic 
acid. The paratartrate of lime so formed, dissolves in hydrochloric acid, and 
is precipitated by ammonia; 

Paratartrates. — These salts are identical in composition with the tartrates 
of the same base, but only a few of them have been examined. Paratartrate 
of lead is an insoluble white powder. Paratartrate of antimony and potash is 
prepared in the same way as tartar emetic, and has the same composition, but 
differs in crystalline form, being in four-sided prisms, of a rhombic base, or 
in needles grouped about a centre. Paratartaric acid has little disposition to 
form double salts. 

According to the observations of Fremy, crystallized paratartaric acid loses 
water when heated, and gives rise to two new and peculiar acids, corresponding 
in composition with tartralic and tartrelic acids. At a still higher temperature, 
it gives rise to a body which is identical in properties with anhydrous tartaric 
acid. It gives also by dry distillation the same two pyrogen acids as tartaric 
acid. 



SECTION VI. 



MALIC ACID. 

Formula of the hydrated acid; 2HO-f-C 8 H 4 3 . Malic acid is bibasic 

(Hagen.) 

This is the acid of apples, from which it derives its name, but is of frequent 
occurrence in other acidulous fruits and vegetable juices, where it is accom- 
panied by citric and tartaric acids. It is generally prepared from the berries 
of the mountain ash (Sorbus acuparia.) The fruit is collected in August, 
while scarcely red and before it is ripe. It is bruised in an iron mortar, the 
juice expressed, filtered through linen, and treated in a basin of copper with 
a thin milk of lime till the mixture commences to change colour. An excess 
of lime occasions a deep green colouration, but the liquid ought to have a 
slight acid reaction, and to retain a reddish-brown colour. When now made 
to boil, a large quantity of a neutral malateof lime precipitates, crystalline and 
granular, which may be taken out as it collects, by means of a colander. After 
this is deposited, a new portion of milk of lime may be added, with the same 
precautions, and a fresh portion of malate of lime is obtained. This salt is 
washed cold, and introduced while still humid into a boiling mixture of 1 part 
of nitric acid and 10 parts of water, so as to dissolve it. A concentrated solu- 
tion deposites on cooling a large crop of colourless and regular crystals, of the 
acid malate of lime. The addition of acetate of lead to the purified acid ma- 
late of lime, throws down a curdy white precipitate, which contains lime, but 
on allowing it to digest at a moderate heat in an excess of acetate of lead, the 
lime is abandoned, and crystals form in four-sided prismatic needles* grouped 



KINIC ACID. 645 

about a common centre, and possessing a silky lustre, which are neutral ma- 
late of lead, containing 6 atoms of water of crystallization. The acid is now 
obtained by decomposing the malate of lead diffused through water, by a 
stream of sulphuretted hydrogen, the sulphuret of lead separated by filtration, 
and the liquid evaporated, first by the naked fire, and afterwards by a water- 
bath, to the consistence of a syrup. (Liebig.) 

The hydrated acid forms granular crusts, of which the crystallization is 
confused, which are deliquescent. Its solution is very acid; it reduces the 
salts of gold; the dry acid dissolves entirely in alcohol. The crystallized 
acid fuses at 266° or 184° (130° or 140° centig.,) but when kept for some 
time at that temperature, crystalline plates form in it, and gradually increase 
in quantity; these me fumaric, acid, which is sparingly soluble in cold water. 
By dry distillation, malic acid affords water and afterwards a volatile and crys- 
tallizable acid, named maleic acid by Pelouze. • 

Malates. — Malic acid forms both neutral and acid salts with the alkaline 
and magnesian bases, the second atom of base in the acid salts being water. 
The malate of peroxide of iron is the only one which dissolves in alcohol.* 

Maleic acid (hydrated,) 2HO-fC 3 H 2 3 . This acid comes over on the 
brisk distillation of malic acid. It crystallizes in plates or in oblique prisms 
of a rhombic base, is very soluble in water, alcohol and ether, its taste is acid 
and disagreeable. Distilled by a sharp heat it is decomposed, and resolved 
into water and a white volatile matter, anhydrous maleic acid, fusible at 
134°. 6, and boiling at 349°. There exist both a neutral and acid maleate of 
silver, the first containing 2 atoms of oxide of silver, and the last, 1 atom of 
oxide of silver with 1 atom of water as base, so that maleic acid is certainly 
bibasic. 

Fumaric acid, HO-f-C 4 H0 3 ; a monobasic acid, produced by heating malic 
acid, and also existing in fumitory (Fumaria officinalis,) and in Iceland moss. 
The same acid is formed when the malates of an alkaline base are exposed to 
a high temperature. Fumaric acid thus appears to be related to malic acid, 
as pyrophosphoric acid is to phosphoric acid; but Dr. Hagen did not succeed 
in transforming fumaric acid again into malic, by boiling a solution of the for- 
mer. Fumaric acid crystallizes in fine micaceous plates, soluble in 200 
parts of cold water; it is more soluble in hot water and also in alcohol. It 
crystallizes from boiling nitric acid without change. Fumaric acid may be 
sublimed from a spatula, in the open air, without leaving any residue, but is 
decomposed in a great measure when distilled in a retort. A volatile/i/wia- 
ric ether was formed by Hagen; and by digesting the latter with aqueous am- 
monia, fumaramide, C 4 H0 2 -f-NH 2 , which is an amorphous powder, of bril 
liant whiteness, almost insoluble in cold water and in alcohol. 



SECTION VII. 



KINIC OR QUINIC ACID. 

The formula of neutral kinate of silver is AgO-f-C 14 H, l O l , ; of neutral ki- 
nate of lime, CaO+C l4 H 11 1 15 from which it is inferred that the formula of 

* Dr. Hagen on Malic acid ; Memoirs of the Chemical Society of Loudon, vol. i, p. 28. 



646 OILY ACIDS. 

anhydrous kinic acid is C 14 H X ^ r The formula of the crystallized acid is 
C 7 H 6 6 , or C 14 H 12 O l2 =HO+C 14 H 11 11 . But the kinates of lead and 
copper appear to belong to another class, of which the acid is bibasic, and its 
hydrate 2HO-fC 7 H 4 4 ; the formula of the kinate of lead being 2PbO-f C 7 
H 4 4 , and the formula of the basic kinate of copper, CuO,HO-f C 7 H 4 q 4 (Wos- 
kresensky.) 

Kinic acid was discovered, in 1790, by Hoffmann. It exists as kinate of lime 
in the bark of all the quinquinas, and according to BerzeJius, accompanies gal- 
lic acid in the labernum of many trees. In preparing quinine and cinchonine, 
by boiling the bark of quinquina with hydrochloric or sulphuric acid, and pre- 
cipitating the alkali from the extract by an excess of lime, the kinate of lime re- 
mains dissolved, and is deposited from the solution evaporated to a syrupy con- 
sistence in the state of crystals. The salt is decomposed by heating gently for 
several hours a mixture of 65 parts of it, with 1 part of concentrated sulphuric 
acid diluted with 10 parts of water. The supernatant liquid is drawn off from 
the precipitated sulphate of lime, alcohol added to it so as to throw down the sul- 
phate of lime remaining in solution ; and finally, the clear solution is evaporated 
by a moderate heat to a syrupy consistence, and left to itself. The kinic acid 
crystallizes in voluminous crystals derived from a prism of rhombic base, 
greatly resembling tartaric acid ; they are persistent in air, (Liebig's Traite, 
ii, 122.) 

Kinic acid is soluble in 2 parts of boiling water ; it is also soluble in alcohol. 
By dry distillation it yields a volatile crystalline acid, of which little is known. 
Kinic and gallic acids appear to be related ; indeed gallic acid, which is C 7 H 3 
5 , may be considered as a kinic acid C 7 H 4 4 , in which 1 equivalent of hydro- 
gen is replaced by 1 equivalent of oxygen (Liebig.) 

Kinates. — All the kinates are soluble in water, with the exception of the ki- 
nate of lead containing 2 atoms of oxide of lead ; alcohol precipitates them from 
their aqueous solutions. 

Kinoi'le is a product of the calcination of a kinate by a gentle heat, and of the 
action of peroxide of manganese and sulphuric acid upon crystallized kinic 
acid. It is a remarkable neutral substance, of a golden yellow colour and high 
lustre, heavier than water, fusing and volatilizing without decomposition at 212° 
(Woskresensky.) 



SECTION VIII. 



VOLATILE ACIDS OF BUTTER. 

Butyric acid, H0,C 8 H 5 i0 3 (Chevreul.) This is an oily limpid liquid, 
having the odour of rancid butter and a nauseous and ethereal taste. Its den- 
sity is 0.9765 at 77° ; it evaporates easily in the. open air, and boils above 212°. 
By distillation butyric acid gives butyrone, C 6 H 6 (Kraues,) the formula of 
butyric acid being supposed C 7 H 6 3 (Loewig.) 

Caproic acid, HO-f-C, 2 H 9 3 (Chevreul,) is an oily limpid liquid, having the 
odour of sweat and a nauseous taste, with a sweetish after-taste of apples. Its 
density is 0.922 at 71.°8, it evaporates in open air, boils above 212°, is solu- 
ble in 96 parts of water at 44°.6. It is miscible with alcohol, ether and 
oils. 

Capric acid, H0-fC l8 H l4 3 (Chevreul,) when liquid, greatly resembles 



VOLATILE ACIDS OF BUTTER. 647 

caproic acid in physical properties. When agitated at 52°. 7 it forms a mass of 
fine needles, which become entirely liquid at 64°. 4. It has the same odour as 
caproic acid, with that also of the goat. It is dissolved by alcohol in all pro- 
portions, and is soluble in 6 parts of water at 68°. 

When butter is melted with water, buttermilk, cheese and other impurities 
are separated from it, and the pure oil rises to the surface. It consists of mar- 
garine, oleine, butyrine, caprone, and caprine. The three latter are in small 
quantity, but it is to them, that the peculiar pleasant smell and taste of fresh 
butter are owing. They are compounds of oxide of glyceryl (page 596) with 
butyric, caproic and capric acids. 

Hircic acid, was discovered by Chevreul in the fat of the goat; its composi- 
tion is unknown* 

Phocenic or delphinic acid, HO-J-C ]0 H 7 O 3 (Chevreul;) another volatile 
acid contained in train oil or seal oil, and in the berries of Viburnum opuhts. 
Phocenic acid is a colourless liquid which burns like a volatile oil; its taste is 
nauseous and ethereal, its density 0.932 at 82°. 4, its boiling point above 212°; 
it dissolves in 18 parts of water at 86°. 

All these volatile acids are obtained in the same way. The fat oil which 
they accompany is saponified by an alkali, and the soap decomposed by an 
excess of tartaric acid, in which the volatile acids are soluble, and may thus 
be separated from the fat insoluble acids. The volatile acid is then converted 
into a salt of barytes by adding barytes-water to it, and thus precipitated. 
The barytic acid is again decomposed by phosphoric or sulphuric acid, and 
the volatile acid thus set at liberty is rectified by the heat of a water-bath; it 
is then purified completely from water by means of fused chloride of calcium. 
These volatile acids form but a small proportion of the butter and oil in which 
they are found. 

Cevrtdic acid exists in the fat extracted by ether from the seeds of Veratrum 
sctbadilla. It forms by distillation a sublimate of white needles of a silky 
lustre, fusible at 68° (Pelletier and Caventou.) It is named also aabtidillic 
acid, 

Verafric acid (dried at 212°) HO + C I3 H 9 7 , is obtained by exhausting 
the seeds of cevadilla by alcohol and sulphuric acid, and neutralizing the alco- 
holic extract by hydrate of lime; veratrine and other products precipitate, but 
veratric acid remains in solution combined with lime, and is obtained by de- 
composing its salt of lime with hydrochloric acid. Veratric acid forms short 
thin quadrangular prisms, colourless and having a slightly acid taste. Its so- 
lubility in cold water is small, but it is more soluble in hot water, dissolves 
easily in hot alcohol and crystallizes on cooling; it is insoluble in ether. The 
crystals lose water at 212°, and become then of a dull white. They fuse at 
a high temperature into a colourless liquid, and sublime without residue. 
Fuming nitric acid and concentrated sulphuric acid have no destructive action 
on veratric acid (Merck.) The alkaline veratrates are crystallizable, and very 
soluble in water and alcohol; the salts of lead and silver are insoluble in water, 
but soluble in alcohol. Vrratric ether, EO-fC 18 H 9 7 (Dr. Will,) is a crys- 
talline radiated, very friable mass, of density 114.1, fusing at 107°. 6 (42° 
centig.,) and imperfectly volatile. 

Crotonic acid, termed also Iatrophic acid, is derived from croton oil, the 
fat oil of the seeds of Croton tig/ium, in the same way as the preceding acid. 
It is solid, very volatile and highly poisonous (Pelletier and Caventou.) 



648 OILY ACIDS. 



SECTION V. 



OILY ACIDS OF BUTTER OF COCOA, BUTTER OF NUTMEGS, AND 

PALM OIL. 

Cocinic acid, termed also Cocostearic acid, HO-f C 27 H 26 O g (Bromeis) is 
the crystallizable acid of the butter of the cocoa-nut. This butter is obtained 
by expressing the dry fruit between hot plates; it is white and possesses the 
consistence of fat, and is distinguished from other fatty bodies by its great 
solubility in alcohol. 

The mode of preparing cocinic and all the other oily acids is similar. The 
butter of cocoa is boiled with a solution of an alkali, and thus saponified; the 
soap is then decomposed by a mineral acid, and the concrete fat acids which 
appear are expressed repeatedly between folds of blotting paper, till the latter 
no longer absorbs liquid matter. The expressed solid matter is saponified 
anew with soda, the soap dissolved in water, and separated by dissolving com- 
mon salt in the water; the soap thus prepared is again decomposed by tartaric 
acid. Finally the fat acid thus obtained is purified by crystallizing it repeat- 
edly from alcohol till its point of fusion becomes fixed (Liebig.) Cocinic 
acid is inodorous, of a brilliant white, fuses at 95°, and forms on cooling an 
amorphous diaphanous mass, like porcelain, is insoluble in water. It may be 
distilled without change. The corinates of alkaline bases considerably resem- 
ble the soaps of the other oily acids. 

Sericic or Myristic arid, HO-f-C 2 8 H 2 7 3 (Playfair.) This acid is obtained 
from the solid portion of the butter of nutmegs, the fruit of Myristica moschata, 
in which it is combined with glycerine. This solid portion dissolves completely 
in 4 parts of boiling alcohol, by which it may be easily distinguished from other 
soluble fat bodies, and gives on the cooling of the liquid, the sericate of glyceryl 
in thin silky needles. 

Sericic acid, which was discovered by Dr. Playfair, crystallizes in white 
brilliant plates, of a silky lustre, (hence the name, sericic acid;) it fuses between 
118°. 4, and 120.°2 (48° and 49° centig.,) and on cooling becomes a mass, 
having a very distinct crystalline structure. It is very soluble in alcohol and 
ether, insoluble in water. It is decomposed by dry distillation, and violently 
attacked by nitric acid. Sericates of alkaline bases are distinguished from 
other soaps by crystallizing from alcohol; their solutions do not become viscid 
and thready by concentration, nor are they disturbed by the addition of much 
water (Playfair.) Sericic ether is an oily, colourless liquid, of density 0.864. 
Sericine, or sericate of glyceryl, contains as base oxide of glyceryl minus 2HO, 
or C 6 tt 5 3 ; its formula being C ll8 H ll3 15 «±4(C, 8 H ay 3 )+C e H J 03. 

Palmitic acid, HO+C 32 H 31 3 (Fremy, Stenhouse.) A soap of the palm 
oil of commerce yields when decomposed by an acid, a mixture of palmitic 
and oleic acids; which mixture, dissolved in boiling alcohol, gives crystals of 
palmitic acid on cooling. Purified by repeated crystallization from alcohol, 
palmitic acid forms brilliant plates, w 7 hich completely resemble those of mar- 
garic acid, and have the same point of fusion, 140° ; it is insoluble in water. It 
dissolves in alkaline carbonates, and forms a transparent emulsion. After 
being heated to 572° (300° centig.,) palmitic acid does not crystallize from alco- 



margaric and stearic acids. 649 

hoi in leaflets, but in mammillated masses, which, however, have precisely the 
same composition (Fremy.) Palmitic acid distils with very little alteration. 
Chlorine decomposes the acid when heated, and yields several chlorinated pro* 
ducts, which are less fluid, and acid, but do not combine with bases without 
losing their chlorine. Palmitate of glerceryl or palmitine, when pure is crys- 
talline, and of brilliant whiteness, is very slightly soluble in boiling alcohol, but 
dissolves in boiling ether in all proportions, and is deposited, on cooling, in ex- 
tremely small crystals. From the analysis of Dr. Stenhouse, palmitine is repre- 
sented by C 35 H 33 4 , which is anhydrous palmitic acid C 32 H 31 3 plus 
C 3 H 2 0; the last formula expressing half an equivalent of anhydrous oxide of 
gleyceryl, C 6 H 7 5 , from which 3HO have been subtracted.* 

Ethalic acid (page 598,) termed also cetylic acid, has absolutely the same 
composition as palmitic acid. 



MARGARIC AND STEARIC ACIDS. 

Margaric acid, or Margarylic acid, 2HO-f C 68 H 6S 6 =2HO+2(C 34 H 33 
4-0 3 ;) in the last formula C 34 H 33 represents a radical margaryl (Liebig.) 
This acid forms the principal part of the stearopten, or solid portion of human 
fat and vegetable fixed oils; it is also produced by the dry distillation of ox and 
mutton suet, and of stearic acid. It is most easily obtained in a state of purity, 
by boiling for some minutes stearic acid (the matter composing stearine 
candles,) with an equal weight of nitric acid, of density 1.273 (32° Baume.) 
The mixture is then left to itself, and after expressing the product, which has 
become concrete on cooling, between folds of blotting paper, it is crystallized 
several times successively from alcohol, till its point of fusion remains constant 
at 140° (60° centig.) It may also be obtained by adding acetate of lead to the 
solution of a soap of olive oil, or of human fat; on treating the precipitate which 
falls, by cold or hot ether, margarate of lead remains in a state of purity, being 
insoluble in that menstruum. This salt gives margaric acid, when heated with 
a dilute mineral acid. (Liebig's Traite.) Margaric acid was so named by 
Chevreul from its pearly lustre; in external aspect it greatly resembles stearic 
acid, but is more fusible, the last acid fusing between 158° and 167° (70° and 
75° centig.) 

Margarates. — In the formation of salts of margaric acid, sometimes both its 
atoms of water, and sometimes only one is replaced by another base. The 
ether of margaric acid, which contains 2 atoms of oxide of ethyl (Varrentrapp,) 
is obtained by saturating with hydrochloric acid gas an alcoholic solution of 
margaric acid, and withdrawing the excess of hydrochloric acid by washing the 
product with water. It fuses at 71°. 6, is decomposed by alkalies and their car- 
bonates, and also by dry distillation. A mixed soap of oleate and margarate of 
potash or soda, such as that of olive oil, when dissolved in about eight times its 
weight of hot water, and the solution afterwards diluted by fifty times its bulk 
of water, allows an acid margarate of potash or soda to precipitate, which may 
be purified from a little oleate with which it is contaminated by repeated crys- 
tallization from alcohol. This salt contains 1 atom of water, and 1 atom of 
potash as base. Both the acid and neutral margarates of potash crystallize 
from an alcoholic solution in plates, which have less lustre than the correspond- 
ing stearates. Margarine, or the margarate of glyceryl, has not been analyzed 
in a state of purity. The solid matter which is formed in olive oil when cold, 
is a combination of margarate and oleate of glyceryl, according to Pelouze and 
Boudet. 

* Phil. Mag. 3rd series, xviii. 186. 
55 



650 OILY ACIDS. 

Stearic acid, hypomargarylic acid, 2H04C 68 H 66 5 ==2HO-f-2(C 34 tl3 3 ) 
-f0 5 . — This acid was discovered by Chevreul, combined with oxide of glyceryl 
in animal and vegetable fats and in the bile of many animals. It may be 
obtained pure by crystallizing the stearic acid of commerce from alcohol, till its 
point of fusion is between 158° and 167°. The latter substance, which forms 
the stearine candles of commerce, is obtained by saponifying tallow with hydrate 
of lime, to get rid of its oxide of glyceryl which being set free dissolves in water, 
and decomposing the insoluble soap of lime with dilute and boiling sulphuric 
acid. The oleic acid is separated from the stearic acid by submitting the latter 
to pressure between hot metallic plates. The cake thus obtained is said to 
contain not more than traces of margaric and oleic acids. Mixed stearic and 
oleic acids may also be separated by solution in boiling alcohol, from which the 
stearic acid crystallizes out, and may be purified by successive crystallizations 
from alcohol. 

Stearic acid crystallizes by cooling in white brilliant needles, soft to the touch* 
pulverisable and insoluble in water. When fused and cast in a mould its sur- 
face is rough from crystalline granulation, but if a minute quantity of finely 
pulverized talc (French white) be mixed with the melted acid, it then solidifies 
with a perfectly smooth and glossy surface like that of wax. Arsenious acid 
was improperly used at one time to produce the effect described in stearine 
candles. Stearic acid fuses at 167°, and solidifies at 158° (Chevreul;) its den- 
sity when solid is 1.01, in the liquid condition 0.854. It is tasteless and inodo- 
rous, fused by heat or dissolved in alcohol it reddens litmus ; it dissolves in its 
own weight of ether of density 0.727, when heated in air it burns like wax. 
Stearic acid is decomposed by dry distillation, and resolved into margaric acid 
and oxide of margaryl. Nitric acid with heat decomposes it producing first 
margaric acid, and afterwards suberic and succinic acids. Stearic acid is dis- 
solved entirely by sulphuric acid with a gentle heat, without colouration, and is 
precipitated on the addition of water in the form of white flocks. It may thus 
be separated from sulphate of glyceryl, and in a great measure from oleic acid. 
Stearates. — Stearic acid is bibasic and forms two classes of salts in which 
one or both of its basic atoms of water are replaced by a metallic oxide. In 
the cold, stearic acid only decomposes the alkaline carbonates partially, so as to 
produce a bistearate and bicarbonate, but with heat it decomposes the same 
carbonates completely. The neutral stearates of alkaline bases dissolve without 
alteration in 10 or 20 parts of hot water, but the addition of a large quantity of 
water causes decomposition, and an acid stearate precipitates while the liquid 
becomes strongly alkaline; the cooling of a hot solution of a stearate in a small 
quantity of water is attended with the same decomposition, and causes the 
whole mass to assume a gelatinous consistence. The acid stearate of potash 
contains HO-f-KO as base; obtained by precipitation of the neutral stearate in 
solution by 1000 parts of cold water, and crystallized from alcohol it forms 
white pearly plates. Boiling water still farther decomposes this stearate, 1000 
parts of the former producing with the latter a turbid and viscid liquid, which 
becomes liquid and transparent at 167°, and deposits pearly plates between 
138°.2 and 78°.8 (59° to 26° centig. ;) 3 atoms of the acid salt are then resolved 
into 1 atom of the neutral stearate of potash (containing 2KO as base) which 
remains in solution, and into a bistearate of potash (containing KO-f3HO as 
base to 2 atoms of acid,) which remains in suspension in the liquid. Again, by 
the cooling of the solution of the neutral stearate of potash, a portion of the 
former acid stearate of potash is deposited, and half of the alkaline base remains 
in solution. The precipitate is therefore a mixture of bistearate and acid stearate 
of potash. If exposed again to boiling water it ends by being converted 
entirely into bistearate. The solutions of the stearates of alkaline bases are 



DRY DISTILLATION OF MARGARIC AND STEARIC ACIDS. 651 

precipitated by salts of all the other metallic oxides, insoluble stearates being 
formed. 

Stearine, or the acid stearate of oxide of glyceryl is the essential part of all 
kinds of suet; it may be obtained by fusing purified mutton suet by a water 
bath, dissolving it in 8 or 10 times its volume of ether, allowing the solution 
to cool, which becomes a thick mass, and washing the expressed solid matter 
with ether. It forms white pearly plates, fuses at 140° or 143°. 6 (60° or 62° 
centig.,) and on cooling again forms a solid pulverizable mass which is not 
crystalline. It dissolves in 6 or 7 parts of boiling alcohol. This stearate in 
combination with the oleate of glyceryl' forms the solid portion of the butter 
of cacao. According to the analysis of Liebig and Felouse, stearine may be 
represented by C 6 H 7 5 HO,C 68 H 66 5 -f-HO, or by ! atom of hypomar- 
garylic acid combined with 1 atom of oxide of glyceryl and 1 atom of water 
as bases, with an additional atom of water of crystallization. 



PRODUCTS OF THE DRY DISTILLATION OF MARGARIC AND STEARIC 

ACIDS. 

Stearic acid distilled in a vessel about two thirds filled with the acid, yields 
first a white solid product, which fixes at 156°. 2 (69° centig.,) and is a mix- 
ture of margaric acid fusible at 140°, of a crystalline neutral body margarone fu- 
sible at 170°. 6, and of a liquid hydrocarbon in small quantity. The last half 
of the distilled product is generally softer and accompanied with inflammable 
gases; and towards the end the residue blackens and assumes the consistence 
of tar. When stearic acid is distilled with one fourth of its weight of quick- 
lime, a soft buttery mass is obtained, consisting in a great measure of the li- 
quid hydrocarbon and margarone. The products of the distillation of mar- 
garic acid are similar. (Redtenbacher and Varrentrapp.) 

Margarone, C 33 H 33 0, was discovered by Bussy. It is formed by the dry 
distillation of margaric and stearic acids alone or mixed with quicklime; it may 
be freed from adhering margaric acid by caustic ley in which margarone is in- 
soluble, and purified by crystallization from alcohol. It is a white very friable 
pearly mass, and becomes electrical by friction. It is volatilized completely 
from a slip of platinum, but when distilled in a retort it leaves a residue of 
charcoal. It is soluble in 50 parts of alcohol of 0.837, and in 65 parts of ab- 
solute alcohol, and crystallizes upon the cooling of these solutions. Marga- 
rone is also soluble in ether, concentrated acetic acid, oil of turpentine and the 
liquid fats. Obtained from the distillation of stearic acid and lime, the point 
of fusion of margarone may rise so high as 18^>°.8 (86° centig.) after repeated 
crystallization, it must be then a different substance. From the analyses of 
margarone fusing at 170°. 6 by Bussy, Redtenbacher and Varrentrapp, which 
agree, it follows that margarone is produced when margaric acid loses the ele- 
ments of 1 atom of carbonic acid. Margarone is also produced in the distil- 
lation of stearic acid, and it .is supposed possible by M. Liebig that the car- 
bonic acid may come from the decomposition of the margarone, 2 atoms of 
hydrated stearic acid, which, indicating C 34 H 33 by R, would be R 4 O 10 + 
4HO, are resolved into — 

3R+90+3HO = Margaric acid, 
R-f 0+ HO = Oxide of margaryl. 

Two atoms of oxide of margaryl (a hypothetical compound) would contain 
the elements of a hydrocarbon C 66 H 66 , of 1 atom carbonic acid C0 3 and 1 
atom of carbon C. 



652 . OILY ACIDS. 



The matter fusible at 186°.8, which Bussy named slearone may from his 
analysis be represented by 2R-f 0. 



ACID PRODUCTS OF THE ACTION OF NITRIC ACID ON MARGARIC AND 

STEARIC ACIDS. 

When stearic acid is heated with an equal volume of nitric acid of 1.284, 
an abundant disengagement of deutoxide and peroxide of nitrogen takes place 
as soon as the mixture boils. If the mixture is then allowed to cool the stearic 
acid separates apparently unaltered, but really converted entirely into margaric 
acid, while the nitric acid contains no foreign substance in determinable quan- 
tity. By the prolonged action of the boiling acid on margaric acid, the latter is 
gradually but completely dissolved, and the more readily if the nitric acid be 
renewed from time to time; the solution then contains suberic acid, succinic 
acid and an oily substance soluble in nitric acid. (Bromeis.) 

Suberic acid, HO-J-C 8 H 6 Q 3 .— Brugnatelli first obtained this acid by the 
action of nitric acid upon cork (page 518.) It is prepared by evaporating the 
solution of stearic or margaric acid in nitric acid to one half and allowing it to 
rest; the solution in 24 hours becomes a semi-solid mass, which is thrown 
into a funnel to drain, and washed with cold water. When expressed and 
crystallized several times it forms pure suberic acid. Suberic acid when hu- 
mid fuses between 122° and 129°. 2 (50 to 54° centig.,) but when dried in air 
or in vacuo, between 244°.4 and 248° (118 to 120° centig.;) it is distilled 
without alteration. Suberic acid is sparingly soluble in cold water, but dissolves 
in 1.87 parts of boiling water, in 0.87 of boiling alcohol, also in 10 parts of 
cold and 6 parts of boiling ether. Suberate of lime distilled with an excess 
of quick-lime gives among other products a colourless liquid, which boils 
at 374°, and remains liquid at 10°.4 ( — 12° centig.,) of which the compo- 
sition is expressed by C 8 H 7 0. 

Succinic acid, HO + C 4 H 2 3 ; and when sublimed HO+2C 4 H 2 3 . 
This acid has long been derived from the distillation of amber (page 614) and 
exists according to several observers in the resin of some Conifer as. The 
mother liquor which remains after the separation of suberic acid in the pro- 
cess described above, contains succinic acid soiled with suberic acid. The 
solution with the washings of the suberic is evaporated to crystallization, the 
product dried and treated with ether in the cold, which easily dissolves sube- 
ric acid while it leaves the succinic acid behind in a great measure. The latter 
may be purified completely by sublimation. 

The crystals of succinic acid are colourless and inodorous, of density 1.50, 
have a somewhat acrid taste, and sublime without decomposition. This acid 
may be obtained quite anhydrous by several distillations, and then condenses 
as drops in the receiver. The hydrated acid dissolves in 2 parts of boiling 
and 5 parts of cold water; it is equally soluble in alcohol and ether. Hy- 
drated succinic acid sublimes at 284°; fuses at .356° losing one half of its 
water, and boils at 455°. This acid is not sensibly affected by chlorine or 
nitric acid; added to potash in fusion it gives oxalic acid. Hydrated succinic 
acid absorbs the vapour of anhydrous sulphuric acid, and the compound losing 
the elements of one atom of water forms a new acid, of which the salt of lead is 
expressed by 4 PbO + C 8 H 2 S 2 0, . 

Succinates. — The constitution of this class of salts is still doubtful. Ac- 
cording to Fehling the acid is really tribasic, 3HO+ C 8 H. { 5 ; the basic salt 
of lead dried at 428° being 3PbO-f C 5 H 3 5 . In the salt of silver and other 
succinates only two atoms of metallic oxide are found, the third atom of base 
being water. Neutral succinate of ammonia is much used to separate per- 



OLEIC ACID. 653 

oxide of iron from oxide of manganese and other metallic oxides; both the 
reagent and metallic solution must be exempt from free acid, as otherwise the 
succinate of iron will dissolve in the washings. The formula of succinamide 
is NH 2 -r-C 4 H 2 2 , of bisuccin amide NH 2 + C 8 H 3 4 . The last compound 
when dissolved in water assumes 2HO, and forms fine rhomboidal crystals; 
the solution of these crystals has no action upon metallic salts, and therefore 
does not contain succinic acid. 



SECTION II. 



OLEIC ACID AND ACIDS RELATED TO IT. 

This acid has been less successfully investigated than stearic acid, and is- 
probably a mixture of two different principles as it is generally obtained. It 
forms the essential part of the fat oils which are not drying, such as oil of olives 
and oil of almonds, from the last of which it is most advantageously prepared, 
and it is found in less considerable quantity in tallow, solid fats, human bile 
and old cheese. The acid derived from a soap of the fat oil of sweet almonds 
is mixed with its weight of pulverized oxide of lead, and after the mixture is 
digested on a water-bath for several hours, twice its bulk of ether is added to 
it, and the whole left to itself for 24 hours. There is thus formed margarate 
of lead which is insoluble, with an acid oleate of the same base, which is 
soluble in ether. The ethereal solution is then decomposed by dilute hydro- 
chloric acid, which sets at liberty the oleic acid; the last coming to the sur- 
face of the mixture with the ether, and forming an oily limpid stratum. The 
ether is expelled by evaporation, and the oleic acid saponified by an alkali. 
The soap is purified by dissolving it in water and separating it by means of 
common salt; these operations being several times repeated. At last, when 
the soap is colourless, it is dissolved in water and decomposed by tartaric acid; 
the oleic acid thus liberated is washed with boiling water, and dried by the 
water-bath (Liebig's Traite, ii.) It may be prepared by the same process 
from the liquid product obtained in the manufacture of stearine candles. The 
formula for oleic acid established by M. Varrentrapp is C 44 H 39 4 . 

Oleic acid forms an oil which is colourless or of a yellowish tint, has a very 
weak odour, an acrid taste, reddens litmus strongly, is lighter than water, and 
becomes a mass composed of crystalline needles a few degrees above the freezing 
point of water. It is insoluble in water, but mixes with alcohol of 0.822 in all 
proportions. Sulphuric acid colours oleic acid. Nitric acid w r ith oleic gives 
suberic acid, among other products, but no oxalic acid. Peroxide of nitrogen 
or nitrate of suboxide of mercury transforms oleic acid into ela'idic acid. 

Oleates. — Oleic acid decomposes the alkaline carbonates ; its compounds are 
soft, have the appearance of soap and dissolve better in alcohol than in water. 
Oleine, the oleate of oxide of glyceryl, forms the greater portion of the fat oils 
and of most of the solid fats found in nature. It is mixed in these with marga- 
rine or stearine, either of which is deposited in the solid state, when the oil is 
exposed to great cold, the oleine may then be separated by expression of the solid 
matter, although never in a state of purity. According to Pelouze and Boudet 
there are two species of oleine, the liquid portion of such fats as are not drying 
but disposed to become rancid, differing from the liquid portion of the drying 
oils, in solubility, and particularly in the transformation which it undergoes under 
the influence of hyponitric acid into elaidine and elaidie acid, while the oleine of 
drying oils undergoes no sensible alteration in the same circumstances. The 
neutral oleate of potash is deliquescent in a damp atmosphere, dissolves com- 

55* 



654 OILY ACIDS. 

pletely in 4 parts of water, forming a viscid syrup, and is decomposed by a 
greater excess of water and resolved into potash and an acid oleate of potash. 
The latter salt is insoluble in water, but dissolves easily in hot or cold alcohol. 
Oleate of soda dissolves in 10 parts of water at 89°.6. Oleate of lead is soluble 
in ether. 

Sebacic acid, HO-fC 10 H 8 O 3 . Oleic acid from both the drying and non- 
drying oils, from tallow and every other source, affords among the products of 
its dry distillation a matter which becomes concrete on cooling and is sebacic 
acid, easily recognised by its solubility in water and its property of giving a 
white precipitate with a salt of lead. This acid is prepared by washing with 
boiling water the solid and liquid products of the distillation of oleic acid or any 
of the fats which contain oleic acid, so long as the solution gives crystals on 
cooling. These crystals are washed with cold water, and crystallized repeat- 
edly from boiling water till they are colourless and free from empyreumatic 
pdour. 

Sebacic acid greatly resembles benzoic acid in appearance, and crystallizes 
in white very light plates or needles of a pearly lustre ; it reddens litmus and 
has an acid taste, loses nothing at 212°, fuses at 260.°6, and sublimes at a higher 
temperature without alteration. It is but sparingly soluble in cold water, but 
dissolves easily in boiling water and also in alcohol and ether. 

Sebates. — The solution of sebacic acid throws down white precipitates from 
salts of silver and lead. The sebates of the alkaline bases are very soluble. 
Sebacic ether has been formed in the usual way, by transmitting a stream of 
hydrochloric acid gas through an alcoholic solution of sebacic acid. 

Elaidic acid, C 72 H 6 6 5 . When a non-drying oil is mixed with nitrate of 
suboxide of mercury or with peroxide of nitrogen, it gradually becomes solid. 
This change is due to the transformation of the oleic acid of the oil into elaidic 
acid, which remains in combination with oxide of glyceryl, forming elai'dine 
or the elaVdate of glyceryl, which is solid and crystalline at the usual tempera- 
ture. When nitrate of mercury is used in this experiment a portion of the 
mercury is reduced. To prepare elaidic acid, peroxide of nitrogen produced 
by the action of nitric acid on starch is carried through oleic acid free from 
margaric acid, in a vessel surrounded by cold water. The oleic acid after a time 
concretes into a mass composed of considerable leaflets, which is washed with 
boiling water, then dissolved in an equal bulk of alcohol and left to crystallize. 
Pearly crystals in tables are obtained, which are expressed between folds of 
blotting paper and crystallized several times from alcohol (Meyer.) Elaidic 
acid forms thin leaflets of a silvery lustre, considerably resembling benzoic acid. 
This acid is insoluble in water, sparingly soluble in ether, but highly soluble in 
alcohol, particularly when hot ; the alcoholic solution reddens litmus strongly. 
Elaidic acid appears to distil without change. It decomposes alkaline carbo- 
nates and forms salts which dissolve in 6 or 8 parts of water, producing a 
transparent very thick emulsion. These salts may be crystallized from alcohol. 

Oleic acid, when treated with nitric acid, gives rise to a series of acid pro- 
ducts, discovered by Laurent, many of whose results have since been con- 
firmed by Bromeis. These are, in addition to suberic acid, azelaic acid, HO 
-f-C 10 H 8 O 4 , an acid isomeric with suberic acid, and closely resembling it; 
pimelic acid, HO-f C 7 H 5 3 , which crystallizes in white hard grains; adipic 
acid, HO-f C 6 H 4 3 (Laurent,) or 2H0-f-C 14 H 9 7 (Bromeis;) lipic acid* 
when crystallized, HO + C 5 H 3 4 , when sublimed CjH 3 4 ; azoleic acid,, 
C, 3 H 13 4 . 

When oleic or elaidic acid is heated to dryness in a silver capsule with three 
times its bulk of strong potash ley, the mass being continually stirred till it 
becomes dry, and heated till the potash begins to fuse, the materials swell 
considerably, and much hydrogen gas is evolved. The yellowish-browR 



ACIDS OF CASTOR OIL. 655 

saline mass contains a new fat acid, besides much acetic acid. This acid, 
which is the same from both oleic and elaYdic acid, crystallizes when sepa- 
rated in thin needles of brilliant whiteness, fusible at 143°.6 (62° centig.) It 
has been studied by M. Varrentrapp, who represents it by HO+ C 32 H 3o Q 3 ; 
which differs only from palmitic and ethalic acids by containing an atom less 
of hydrogen. 

ACIDS OF CASTOR OIL. 

Castor oil differs considerably from the other fixed oils, particularly by its 
solubility in alcohol. A soap of this oil, when decomposed by a mineral acid 
gives a solid and a liquid oily acid. The first is termed margaritic acid by 
Bussy and Lecanu; it fuses at 266°; the second is named ricinic acid. 

Nitric acid gives with castor oil an acid, named cenanthylic acid by Mr. 
Tilley, from its relation in cenanthic acid. The formula of (enanthylic acid 
is HO + C 14 H 13 3 (Tilley.) According to Bromeis, cenanthylic acid is. 
identical with the azoleic acid of Laurent. 

Castor oil solidifies with nitrate of suboxide of mercury, or with peroxide 
of nitrogen, and forms a yellow transparent mass like wax. The mass washed 
with water and dissolved in boiling alcohol furnishes palmine in confused crys- 
talline grains. Alkalies saponify palmine like elaYdine, disengaging glycerin, 
and combining with palmic acid. This acid, when pure, crystallizes in white 
silky needles, grouped about a common centre, is fusible at 122°, and dis- 
solves with facility in alcohol and ether. Palmine and palmic acid are also 
formed by the action of sulphurous acid gas on castor oil. 



ACIDS FORMED BY THE ACTION OF SULPHURIC ACID ON THE 

FAT OILS. 

When sulphuric acid is added in small proportion to fat oils, its action is 
limited to the abstraction of their glycerin, with which it combines and forms 
sulphoglyceric acid (page 597,) while the oily acids are set at liberty. Such 
is the reaction that occurs when tallow or hog's lard is mixed with half its 
weight of sulphuric acid. But when the proportion of sulphuric acid is in- 
creased, particular compounds of that acid with the oily acids are produced, 
which dissolve in water. The compound^ thus formed by acting upon olive 
oil with concentrated sulphuric acid have been carefully studied by M. 
Fremy.* 

Oleic acid and concentrated sulphuric acid combine directly, and form sul- 
pholeic acid, a double acid. Pure margaric acid dissolves in sulphuric acid, 
but does not form a stable compound, for it is separated by water without 
having undergone any alteration; but when mixed with a certain quantity of 
oleic acid, both oily acids combine with sulphuric acid, and sulphomargaric 
acid is formed with sulpholeic acid. These two compounds are equally 
formed, together with sulphate of glycerin, when half a volume of concen- 
trated sulphuric acid is cautiously added by small quantities, to olive oil, any 
elevation of temperature being guarded against. If then mixed with twice its 
volume of cold water, and left at rest for twenty-four hours, the sulpholeic 
and sulphomargaric acids being insoluble in dilute sulphuric come in the form 
of a syrup to the surface of the liquor, while the sulphate of glycerin remains 

* Ann. de Chim. et de Phys. t. kv, p. 113. 



656 VEGETO-ALKALIES. 

in the strongly acid liquid below. After the mixture of sulpholeic and sul- 
phomargaric acids is washed with a little water, it is dissolved entirely in a 
large quantity of water. The solution has an acid and fatty taste, with a bit- 
ter after-taste, may be neutralized by an alkali without decomposition, and 
the salt thus formed occasions in metallic solutions precipitates insoluble in 
water, and slightly soluble in alcohol. 

Left to itself, the mixture of sulpholeic and sulphomargaric acid undergoes 
decomposition; when the solution is made to boil, the decomposition is instan- 
taneous. The sulphuric acid then separates from the elements of the oleic 
and margaric acids, and these last are themselves transformed into new acids; 
the margaric acid yielding metamargaric acid and hydromargaritic acid, the 
oleic acid, metoleic acid and hydroleic acid. A compound of hydromargaritic 
and metamargaric acid, which has the properties of a single acid, has been 
named hydromargaric acid, by Fremy. These compounds are oily bodies 
insoluble in water, of which those related to margaric acid are solid, and 
those related to oleic acid liquid at ordinary temperatures. These acids have 
been also examined by Varrentrapp and by Mr. Miller, but their composition 
is still involved in considerable uncertainty. 

When metoleic and hydroleic acids are distilled, they are decomposed and 
resolved into two hydrocarbons of the olefiant gas type; elaene. } C 18 H 18 , a 
white substance, boiling at 230°, and oleene, C, 2 H 12 , a colourless ethereal 
liquid. Elaene combines with chlorine, with the evolution of hydrochloric 
acid, and forms an oily compound (Fremy.) 



ACROLEINE. 

Oils and fats boil at a high temperature, giving off carbonic acid with a 
little inflammable gas, and a substance possessed of a most pungent odour, 
which attacks the eyes most painfully, and is named acroleine. The pure 
oily acids do not yield this substance, but only their compounds with oxide 
of glyceryl, proving that the acroleine comes from the glycerin. It is, indeed, 
produced in large quantity by the distillation of pure glycerin. Hence the 
occurrence of acroleine among the products of the distillation of a fat or oil is 
a sure and delicate test of the presence of glycerin in the oil. 

Acroleine is unknown in a state of purity. It absorbs oxygen with great 
rapidity from the air and becomes acid. Its solution is decomposed even in 
close vessels, and yields a tasteless, inodorous, and very indifferent white 
solid, not resembling fat, and insoluble in all menstrua yet tried. No com- 
pound of acroleine has been formed from which it can again be obtained* 
(Liebig.) 



CHAPTER IX.. 



VEGETO-ALKALIES. 



In the class of organic bases are included a number of bodies containing 
nitrogen, which have the properties of the basic or metallic oxides, and form 



VEGETO-ALKALTES. 657 

salts with acids. These salts perfectly resemble salts of metallic oxides; the 
acids which they contain continue to be affected by the usual reagents, sul- 
phate of morphine and sulphate of soda being equally precipitated by chloride 
of barium, and the organic bases themselves are liberated by stronger bases. 
Oxide of ethyl and oxide of methyl are likewise bases, but in salts of these, 
acids have their properties disguised, and can no longer be transferred to other 
bases such as the metallic oxides, by double decomposition; the compounds 
of the last mentioned bases with acids diverge, therefore, widely in their pro- 
perties from common salts. The present class of organic bases are princi- 
pally derived from plants, and are known as the vegeto-alkalies. The solu- 
tions in water of such of them as are soluble in that liquid, and their solutions 
in alcohol restore the blue colour of reddened litmus and render yellow tur- 
meric paper brown; they are therefore unequivocally alkaline. The following 
organic bases appear to be allied to the class of vegeto-alkalies, ammeline. 
melamine, aniline or crystalline, urea, with certain bases still problematical 
which Unverdorben derived from volatile animal oil (oil of Dippel,) namely, 
odorine, ammoline and animine. 

The investigation of this class of bodies was commenced by Derosne, who in 
1803 observed narcotine, and by Sertuerner, who, in 1817, recognised in mor- 
phine from opium the first vegetable base. These chemists, were followed by 
others, particularly Robiquet and MM. Pelletier and Caventou, who in cinchona 
bark, nux vomica, and other vegetable matters found organic bases, in which 
the medicinal virtues of the plants resided. The analogy of these bases to me- 
tallic oxides and their valuable applications in medicine have rendered the class 
a favourite study with both chemists and pharmacians. The method generally 
pursued in the preparation of such of these bases as, like morphine, are insoluble 
in water, consists in treating the vegetable substance containing the base with 
a dilute acid which forms a soluble salt with the base. This solution is concen- 
trated by evaporation, and slightly supersaturated with a soluble alkali, ammo- 
nia, hydrate of lime, magnesia or carbonate of soda, by which the vegetable 
base is precipitated coloured and in an impure condition. To free it from 
foreign matters, the base or a salt of it is crystallized from alcohol, or if neither 
the base nor its salt is not much more soluble in hot than in cold alcohol, and 
therefore does not crystallize well from that liquid, the salt is rendered wmite by 
treatment with animal charcoal and repeated crystallization, and the pure base 
finally precipitated by means of carbonate of soda. 

The extraction of bases which are soluble in water and volatile such as coni- 
cine, is more difficult. The leaves, flowers, root, or seeds which contain the 
volatile base are submitted to distillation with a weak solution of caustic alkali. 
The water which distils over is found to be saturated with the organic base, and 
generally contains besides a quantity of ammonia resulting from the decompo- 
sition of a portion of the former. The distilled water is fully neutralized with 
dilute sulphuric acid, mixed in a concentrated state with caustic alkali, and the 
whole digested in a close vessel with ether, which last solvent takes up the 
liberated vegetable base and the ammonia. The ethereal solution being then 
distilled by the heat of a water-bath, the ether and ammonia escape, and the 
vegetable base is left pure in the retort. 

Ammonia is a true type of the organic bases in general containing nitrogen. 
Morphine, quinine, and other members of the class unite directly with hydro- 
chloric acid, as ammonia does, without the separation of water. An atom of 
water likewise enters into the composition of all their salts containing an oxygen 
acid, as in the corresponding salts of ammonia. This will appear on comparing 
together the following formulae, in which morphine C 35 H 20 NO 6 appears 
exactly equivalent to ammonia NH 3 : 



658 VEGET0-ALKAL1ES. 

Hydrochlorate of ammonia, NH 3 +HC1. 

Hydrochlorate of morphine, C 35 H 2 , NO 6 -f HC1. 

Sulphate of ammonia NH 3 -fHO,S0 3 

Sulphate of morphine C 3 5 H 2 NO 6 +HO,S0 3 

Urea even does not form an exception to this rule, but combines directly with 
hydrochloric acid, according to the observation of Hagen. The hydrochlorates 
of the vegetable bases also resemble sal-ammoniac in forming a crystallizable 
double salt with one atom of bichloride of platinum, and with two atoms of 
chloride of mercury, the last corresponding with sal-alembroth. This similarity 
in properties favours the idea that these bases may have a constitution analogous 
to that of ammonia or be amides of an unknown radical, as ammonia is the 
amide of hydrogen. The amides derived from most acids are neutral sub- 
stances, it is true, such as oxamide, NH 2 -{-C 2 2 , succinamide NH 2 -f-C 4 H 9 2 , 
fumaramide, NH 2 -fC 4 H0 2 and benzamide NH 2 -|-C 14 H 5 2 . Urea, however, 
which contains two atoms of amidogen, as it is represented by Dumas, 2NH 2 
-f C 2 2 has a basic character; and melamine is strongly basic, which may be 
represented as Cy»-f-3NH 2 , as cyanuric acid is Cy 3 -f0 3 (Liebig.) But 
although this view of the constitution of vegeto-alkalies is not improbable it 
must be admitted that the radicals which are thus supposed- to be in combina- 
tion with amidogen, in the vegetable bases, have not been transferred from that 
to any other radical, much less isolated. 

Chlorine transmitted through water containing a vegetable base in suspension 
quickly produces hydrochloric acid, and forms a hydrochlorate of the base, 
which is soluble in the water. This salt is decomposed by the continued appli- 
cation of chlorine, generally with a change of colour in the liquid to yellow or 
red, and the formation of a precipitate. The precipitate from the salts of strych- 
nine has been found to contain both chlorine and nitrogen. Quinine and cin- 
chonine salts become with chlorine yellow, rose-red, and then violet-red, while 
a red resinous matter precipitates, which in the air becomes brown, hard, and 
pulverizable. But the nature of the changes which chlorine produces upon these 
bases remains still to be investigated. The action of iodine is more definite. 
According to Pelletier, 2 parts of strychnine and 1 part of iodine dissolved in 
boiling alcohol, give a precipitate on cooling, of yellow crystalline spangles, 
resembling mosaic gold, and hydriodate of strychnine crystallizes out from the 
liquor when concentrated by evaporation. The precipitate appears to contain 
1 i equivalent of iodine. The precipitate produced in brucine, treated with tinc- 
ture of iodine in the same way is yellow; quinine and cinchonine give saffron 
plates by evaporation of the liquid. The vegetable alkalies are recovered 
unaltered from these precipitates, when they are treated with a dilute acid, 
iodine being then liberated or by the action of a solution of caustic potash or 
soda, and then iodide of potassium or sodium is produced at the same time. 
The substance thrown down by the action of iodine upon morphine is of a brown 
colour and differs in nature from the other products as morphine can in no way 
be revived from it. The hydrogen of the hydriodic acid formed with the other 
alkalies appears to come from the water, but to be derived in the last case from 
the decomposition of the vegetable base itself. 

Little is known of the action of acids upon the vegetable bases, with the excep- 
tion of some observations of change of colour which have been made. Thus 
brucine with a slight excess of nitric acid becomes blood-red, while the colour 
of pure strychnine is not changed by the same treatment, so that the presence 
of brucine in strychnine can in this way be detected. Nitric and iodic acids 
colour morphine, and its salts rose-red. Other bases, such as urea and melamine 
are decomposed by the stronger acids ; urea being converted by the action of 



VEGETO-ALKALIES. 659 

concentrated sulphuric acid into carbonic acid and ammonia, by the assumption 
of two atoms of water ; and melamine into cyanuric acid and ammonia, by the 
assumption of three atoms of water. Thebaine also, exposed to dry hydro- 
chloric acid gas, is resolved into sal-ammoniac and a resinous substance having 
acid properties (Kane;) but the other vegetable bases are not found to undergo 
similar decompositions when exposed to acids. 

Curious relations in composition exist between some of the vegetable bases; 
thus cinchonine and quinine appear only to differ from each other, in the latter 
containing an atom of oxygen more than the former : 

Cinchonine C 20 H 12 NO 

Quinine. „ C 20 H 12 NO 3 

Another base, aricine, of which the composition is less certainly determined 
belongs properly to the same group, containing an atom more of oxygen than 
quinine, that is, C 2 H : 2 NO 3 (Pelletier.) These three bases are found together 
in the quinquinas. 

Codeine and morphine, which are found together in opium, appear to have a 
similar relation in composition to each other : 

Codeine > C 3s H 20 NO 5 , 

Morphine > C 35 H 20 NCV 

Narcotine from opium and chelidonine, a base likewise from the family of 
Papaveracez, appear to be related : 

Chelidonine ..... C 40 H 20 N 3 O 6 (Will.,) 
Narcotine C 4l1 H 20 NO l2 (Liebig.) 

The chelidonine contains 2 atoms of nitrogen more than the narcotine, while 
the latter contains 6 atoms of oxygen instead of this nitrogen ; these being equi- 
valent quantities, it will be remembered of the elements in question. Or, by 
adding 2 atoms of ammonia to narcotine and substracting therefrom 6 atoms of 
water, chelidonine would be produced (Liebig.) Attempts, however, which 
have been made to convert one of these bases into the other have not been suc- 
cessful. But the composition assigned above to narcotine is by no means cer- 
tain. The formula for the same base deduced by M. Regnault from his analysis 
is C 44 H 53 NO, 3 ; and that deducible from the atomic weight of its double salt 
with bichloride of platinum is C 43 H 24 N0 15 (Liebig.) 

According to the formula which M. Liebig is inclined to adopt for the two 
bases strychnine and brucine, which also occur together, the latter contains 2 
atoms of water and one atom of oxygen more than the former: 

Strychnine .... C 44 H 2 3N,i0 5 , 

Brucine C^H^N^Oe (Liebig.) 

To the same bases M. Regnault assigns formulae which are somewhat dif- 
ferent, but which are equally compatible with the atomic weight of these 
alkalies as observed in their bichloride of platinum compounds: 

Strychnine C 44 H 23 N 2 4 , 

Brucine C 44 H2 5 N 2 7 , (Regnault.) 

These formulae indicate the same difference of composition between strych- 



660 



VEGETO-ALKALIES. 



nine and brucine, as do the preceding formulas for the same compounds. The 
composition of thebaine from opium, according to the analysis of Dr. Kane is 
expressed by C 25 H 14 N0 3 . The composition of jervine, a base discovered 
by M. Simon in the root of Veratrum album, and carefully analyzed by Dr. 
WillisC 60 H 45 N 2 O 5 . 

Several other organic bases have been analyzed, but those of which the 
composition has been already stated are perhaps the only ones, for which we 
have data to construct formulas of any considerable degree of probability. 
The numerical results of the best analyses which have been made of the re- 
maining bases are given by M. Liebig, as follows:* 





ARICINE. 


ATROPINE. 


CONICINE. 


CORYDALINE. 




Pelletier. 


Liebig. 


Liebig. 


Dr. Dobereiner. 


Carbon 


71.0 


70.98 


66.91 


63.05 


Hydrogen . 


7.0 


7.83 


12.00 


6.83 


Nitrogen. . 


8.0 


4.83 


12.81 


4.32 


Oxygen. . 


14.0 


16.36 


8.28 


25.80 




100.0 


100.00 


100.00 


100.00 




DELPHININE, 

Couerbe. 


EMETINE. 
Pelletier. 


NARCEINE. 




Pelletier. 


Couerbe. 


Carbon. 


76.69 


64.57 


54.73 


57.02 


Hydrogen. . 


8.89 


7.17 


6.52 


6.64 


Nitrogen. 


5.93 


4.30 


4.33 


4.76 


Oxygen. 


7.49 


22.96 


34.42 


31.58 




100.00 


100.00 


100.00 


100-00 




PSEUDOMORPHINE. 


SABADALLINE. 


.:; SOLANINE. 






Pelletier. 


Couerbe. 


Blanchet. 


Carbon. 


. . . 


52.74 


64.18 


62.11 


Hydrogen. . 


. 


5.81 


6.88 


8.92 


Nitrogen. 


. 


4.08 


7.95 


1.64 


Oxygen. 




37.37 


20.99 


27.33 




100.00 


100.00 


100.00 




VERATRINE. 


MENISPERMINE. 

Pellet and Couerbe. 


STAPHISAINE. 




Couerbe. 


Dumas and Pellet. 


Couerbe. 


Carbon 


70.48 


66.75 


71.89 


73.57 


Hydrogen. . 


7.67 


8.54 


8.01 


8.71 


Nitrogen. . 


5.43 


5.04 


9.57 


5.78 


Oxygen. 


16.42 


19.64 


10.53 


11.94 



100.00 



100.00 



100.00 



100.00 



MORPHIA AND THE OTHER BASES IN OPIUM. 

When incisions are made in the heads of the white poppy, (Papaver som- 
niferum) a milky juice exudes, which is allowed to dry by evaporation on 
the plant, then scraped off and collected, it forms opium. This drug has 



* HandwOrterbuch der Reinen und Angewandten Chimie, b. i, 709. 



MORPHINE. 661 

been minutely examined, and several vegetable bases derived from it. Its 
narcotic and anodyne properties are chiefly due to morphine, which is also 
the base that opium contains in largest proportion. 

Morphine or morphia, C 35 H tJ0 NO 6 . — Much soluble matter is extracted 
from opium when treated repeatedly in a divided state with water. Most of 
the narcotine, however, remains in the residuum, from which it may be ex^ 
tracted by dilute hydrochloric acid, or by boiling alcohol or ether. If the 
aqueous solution be greatly concentrated by evaporation, and mixed with a 
strictly neutral solution of chloride of calcium, a brown impure precipitate of 
meconate of lime is thrown down, while the bases are converted into hydro- 
chlorates. The liquid being filtered may be made distinctly acid with hydro- 
chloric acid, then digested, in order to discolour it, with pure animal charcoal 
previously deprived of all phosphate of lime by an acid, filtered again and 
evaporated for crystallization. A radiated crystalline mass is deposited which 
consists of hydrochlorate of morphine in combination with hydrochlorate of 
codeine. This mass may be drained and expressed, then dissolved in hot 
water, and precipitated by ammonia, which throws down the morphine, while 
the codeine remains in solution. By farther concentration of the liquid an 
additional quantity of morphine is deposited; when afterwards an excess of 
caustic potash is added to the liquid, what remains of the morphine is retained 
in solution, and the codeine precipitated. Thebaine, narcotine, <fcc, remain 
in the former brown mother-liquor, which afforded the crystallized double 
salt of hydrochlorate of morphine and codeine. 

Morphine may be prepared, without reference to the other bases in opium, 
by various processes, of which the following appears to be the best. The 
opium is macerated thrice in succession, each time with three parts of cold 
water, and the mass after each digestion strongly expressed. The liquids are 
united, raised to the boiling point, and mixed with an equal bulk of milk of 
lime, the latter containing a quantity of hydrate of lime equal to about one 
fourth of the weight of the dry opium employed. After boiling for a few 
minutes the mixture is strained through linen; all the narcotine, meconic acid, 
&c, remain in the lime precipitate, while all the morphine is contained in the 
solution in combination with lime. This solution is greatly concentrated by 
evaporation, then filtered, heated to the boiling point and pounded sal-ammo- 
niac is thrown into it, in about the proportion of 1 ounce of sal-ammoniac to 
1 pound of opium. The caustic lime is thus converted into chloride of cal- 
cium, the morphine loses its solvent, and is precipitated in small crystalline 
needles. Opium yields upon an average a sixteenth of its weight of morphine. 
(Mohr.) 

Morphine as precipitated by ammonia forms a white pulverulent mass, but 
when crystallized from alcohol it assumes the form of small colourless brilliant 
prisms. It requires 1000 times its weight of water to dissolve it, but tastes 
sensibly bitter, and has an alkaline action. Morphine is scarcely soluble in 
ether, but dissolves in 40 times its weight of cold and in 30 times its weight 
of boiling alcohol; it is very soluble in caustic alkali. It is fusible by heat, 
with the loss of water of crystallization, and on solidifying again forms a 
crystalline mass. Morphine and its salts strike a deep blue colour with the 
solution of a persalt of iron made as nearly neutral as possible; they likewise 
decompose iodic acid and liberate iodine, which may then be detected by solu- 
tion of starch. 

Hydrochlorate of morphine crystallizes in needles or feathery crystals, 

which require from 15 to 20 times their weight of cold water to dissolve them, 

but dissolve in less than their own weight of boiling water. This, which 13 

perhaps the most valuable of the salts of morphine for medical use, is prepared 

56 



662 VEGETOALKALIES. 

directly from opium.* Sulphate of morphine is highly soluble, and crystal- 
lizes like the hydrochlorate. Bisvlphate of morphine has been formed. Acetate 
of morphine crystallizes with difficulty and is apt to lose a portion of its acid 
even when kept in crystals; it is much employed in medicine. Birneconate of 
morphine is a crystallizable salt, in which one of the three atoms of water of 
meconic acid, is replaced by morphine; this salt also is prepared for medical 
use; morphine is supposed to exist in opium in combination with meconic acid. 
The latter acid can easily be detected by re-agents (page 634;) and being found 
in no other vegetable matter but opium, meconic acid is the substance looked 
for in testing for opium, of which it is an infallible index. 

2. Narcotine, C 48 H 24 N0 15 , the first crystalline substance derived from 
opium, is remarkable for its solubility in ether, by means of which it may be 
dissolved out of opium. It forms colourless brilliant prisms, is tasteless, in- 
soluble in water and caustic alkali, soluble in alcohol. Its solution has no alka- 
line reaction, but narcotine dissolves in acids; its salts do not crystallize. 

3. Codeine, C 35 H 20 NO 5 , is remarkable for its solubility in water, being so- 
luble in about 2 parts of boiling water, also in alcohol and ether. It has a 
weak taste, alkaline reaction, and fuses by the heat of boiling water. 

4. Thebaine or paramorphine, C 25 H 14 N0 3 , is crystallizable, has an alka- 
line reaction and sharp taste. 

5. Narceine, a weak base which exists in opium in a very small proportion. 
Two other bases, pseudomorphine and porphyroxine have been discovered in 
certain species of opium. Opium also contains a neutral substance meconine 
in minute quantity, of which the elements are carbon, oxygen and hydrogen 
only. 



QUININE AND CINCHONINE. 

Peruvian bark owes its febrifuge qualities to these bases, which it contains in 
combination with tannic and kinie acids. Quinine is most abundant in yellow 
bark, usually considered as the bark of the Cinchona cordifolia, while cincho- 
nine prevails in the gray (pale) bark considered as the bark of the Cinchona 
nitida or of the Cinchona condaminea. 

The ground bark is boiled in water acidulated with hydrochloric acid, the 
filtered solution mixed with an excess of milk of lime, the precipitate washed, 
expressed and dried. From this precipitate, which contains quinine, cinchonine, 
tannate of lime and other matters, the two bases are dissolved out by boiling 
alcohol ; the solution which is strongly coloured is filtered, neutralized with di- 
lute sulphuric acid and the alcohol distilled off. Sulphate of quinine crystallizes 
on cooling, and is obtained colourless by treatment with animal charcoal and 
repeated crystallization. The sulphate of cinchonine may be obtained from 
the coloured mother liquor. Both bases may be isolated by precipitating a so- 
lution of their salts in water, by means of ammonia. (Woehler.) 

Quinine, C 20 H 12 NO 2 . — This base is precipitated by ammonia in white 
flocks, which are not crystalline, and is crystallized even from solution in alcohol 
with difficulty; but from hot alcohol containing a little ammonia quinine is de- 
posited in fine needles. It is in the state of a hydrate, which fuses about 302° 
and loses the whole of its water. Quinine is very bitter, alkaline, soluble in 200 
parts of boiling water, and highly soluble in alcohol. Most of the salts of this 

* By the process invented by Dr. Robertson and improved by Dr. W. Gregory ; Edin- 
burgh, Medical and Surgical Journal, Nos. 107 and 111, also Jour, de Phar., xix. 156. 



STRYCHNINE AND BRUCINE. 663 

base are crystallizable, intensely bitter and are precipitated by alkalies, bichlo- 
ride of platinum and oxalic acid. 

Subsulphate of quinine, the ordinary sulphate of quinine of the shops, crys- 
tallizes in tufts composed of fine needles, which are very light, slightly flexible 
and have a pearly lustre. It requires 740 parts of water to dissolve it at 55°, 
but only 30 parts at 212° ; it is very soluble in dilute sulphuric acid. It fuses 
with the appearance of wax, and loses 1 1 1 per cent, or 6 atoms of water. The 
crystallized salt contains 2 atoms of quinine and 8 atoms of water to 1 atom of 
sulphuric acid. Neutral sulphate of quinine is formed by adding a little sul- 
phuric acid to a solution of the sub-sulphate ; it crystallizes well in rectangular 
prisms with rectangular or square bases, is soluble in 1 1 parts of water at 55°, 
and fuses in its water of crystallization at 212°. It reddens vegetable blues, 
although its taste is not perceptibly sour but strongly bitter ; it contains 8HO. 

Cinchonine, C 20 H 12 NO. — This base crystallizes readily from alcohol in 
brilliant prisms. It requires 2500 times its weight of boiling water to dissolve 
it, and is less soluble in cold water. It is but slightly soluble in cold ether ; in 
its other properties it resembles quinine. Neutral sulphate of cinchonine crys- 
tallizes also in large octohedral crystals of a rhomboidal base, having a mother 
of pearl lustre ; it contains 8 atoms of water. 



STRYCHNINE AND BRUCINE. 

These alkalies are derived from the Nux vomica class of plants, and particu- 
larly from the seeds of S try clmos nux vomica, and St. Ignatius' bean, the fruit 
of Strychnos ignafia, To extract them, powdered nux vomica is boiled re- 
peatedly in water, the infusion is concentrated to a syrup and mixed with hy- 
drate of lime in the proportion of 2 ounces of quicklime to 1 pound of the nux 
vomica. The two bases are contained in the insoluble portion of the mass, 
which is dried and exposed to boiling alcohol. On evaporating the alcoholic 
solution strychnine crystallizes first, while the brucine and a portion of strych- 
nine remain in the mother liquor. To complete the separation, the bases in 
the mother liquor are neutralized by greatly diluted nitric acid, and the nitrate 
of strychnine crystallized out, while the salt of brucine remains still in solution 
being much later of crystallizing. From the salts, purified as usual by animal 
charcoal, and dissolved in water, the bases may be precipitated by ammonia. 

Strychnine or strychnia, C 44 H 2; ,N 2 4 ; as obtained from the evaporation 
of its alcoholic solution it assumes the form of minute colourless octahedrons, 
eomposed of two four-sided pyramids, between which a four-sided prism is 
sometimes interposed. It is soluble in 2500 parts of boiling and in 6667 parts 
of cold water; but the last solution, weak as it is, has an intensely bitter taste. 
It is insoluble in absolute alcohol and ether, but sensibly soluble in aqueous 
alcohol; not fusible. Strychnine acts with great energy on the animal eco- 
nomy, inducing tetanus. Its poisonous action is best counteracted by an in- 
fusion of gallnuts or warm tea. The salts of strychnine are generally crys- 
tallizable. 

Brucine, C 44 H 25 N 2 7 . — This alkali was first discovered in 1819 by Pel- 
letier and Caventou in the bark of Brucia a.ntidy sent erica. Brucine greatly 
resembles strychnine in its properties, acts in the same way on the animal 
economy but is much less poisonous. It is more soluble in water, and is 
strongly reddened by nitric acid, while pure strychnine is not. 



664 VEGETO-ALKALIES. 



VERATRINE. 

This alkali is found in the seeds of different species of Veratrum, particu- 
larly of Veratrum album or white hellebore, and Veratrum sabadilla, in 
which it exists combined with veratic acid, (page 647.) It is extracted by a 
process similar to that for strychnine. Veratrine has the aspect of a resin, is 
friable and gives a white powder; it cannot be crystallized. It is nearly inso- 
luble in water, but dissolves in alcohol and ether. Its taste is excessively 
acrid and not bitter; with sulphuric acid it becomes yellow, red, and at last 
violet. "Veratrine occasions violent irritation in any mucous membrane to 
which it is applied, and is highly poisonous. Few of its salts except the hy- 
drochlorate and sulphate are crystallizable; they are not precipitated by bichlo- 
ride of platinum. 

Sabadilline is a crystallizable base which accompanies veratrine in the seeds 
of Veratrum sabadilla. Jervine is another base found in the root of Veratrum 
album. 



CONIC1NE. 

This base is also termed conia and coneine; its formula is C 12 H 14 NO. It 
exists in all parts of hemlock, Coniitm maculatum. It is volatile and is ob- 
tained by the distillation of the plant or its seed with a solution of caustic al- 
kali, in the manner formerly indicated. It is a colourless oily liquid, of den- 
sity 0.89, boiling at 302°; its odour is strong and penetrating, recalling at once 
that of hemlock and tobacco. The taste of conicine is acrid and corrosive, 
and it occasions death almost as rapidly as hydrocyanic acid. It is soluble in 
100 parts of water, alkaline, miscible with alcohol' and ether. With sulphuric, 
phosphoric, nitric and oxalic acids it forms salts, which crystallize well. So- 
lutions of both conicine and its salts undergo decomposition when air is ad- 
mitted to them, and become biown with formation of ammonia. 

The following organic bases are well established, besides those already 
enumerated. 

Aconirine, in several species of aconitum. 

J] Heine, in a variety of cinchona bark. 

Atropine, in all parts of Atropa belladonna. This base is soluble in water, 
and is readily decomposed when in solution by heat; it crystallizes in small 
white prisms. Its taste is most disagreeably bitter and acrid. In a state of 
solution, and particularly when in combination with acids, it is easily decom- 
posed with the formation of ammonia. It is highly poisonous, and in the 
most minute proportion possesses the power to dilate the pupil of the eye. 
The formula for atropine is C 34 H 8 N0 6 . 

Che/idonine and ehelerythrine in Chelidonium majus. 

Colchicine in Colchicum autumnale. 

Corydaline in the root of Corydalis bulbosa and fabacea. 

Curarine in the Curara poison of India. 

Daturine in the seeds particularly of Datura stramonium. 

Delphinine in the seeds of Delphinium staphisagria. 

Emetine in ipecacuanha; the root of Cephaelis ipec. It is a white, very 
fusible powder of a feebly bitter taste, sparingly soluble in water, readily so- 
luble in alcohol; it excites vomiting. 

Hyoscyamine in Hyoscyamus nigar and albus. 



CYANOGEN. 665 

Nicotine exists in the leaves and seed of different species of tobacco, namely 
Nicotiana tabacum and Nicotiana rustica. It is soluble in water, has the con- 
sistence of butter and distils at 284°. 

Pelosine in the root of Cissarapelos pareira. 

Solanine in several species of Solanum, and in the first shoots of germi- 
nating potatoes. 

The following bases are not so well known and still problematical: apirine, 
azaridine, blanchinine, buxine, carapine, castine, ehioccine, crotonine, cyna- 
pine, daphnine, digitaline, esenbeckine, eupatorine,euphorbiine, fumarine, glan- 
cine, glaucopicrine, jamaicine, menispermine, peramenispermine, pitayine, 
sanguinarine, staphisaine, surinamine, violine. Besides two bases in Car- 
thagena quinquina bark and in chinova bark. (Liebig.) 



CHAPTER X. 



CYANOGEN AND ITS COMPOUNDS. 

Cyanogen, NC 2 = Cy, which when free, is a gas (page 304,) is remarka- 
ble as an organic radical, and enters as a constituent into a large class of com- 
pounds. It combines directly with hydrogen, forming a hydrogen-acid, with 
the whole of the metals forming salts, and is also obtained in combination with 
oxygen forming several acids, and with chlorine. Cyanogen also appears to 
be a constituent of urea and uric acid, and of the numerous bodies derived 
from the decomposition of the latter. 

Formation of cyanogen. — This compound is always primarily obtained as a 
constituent of ferrocyanide of potassium (page 318.) In order to explain the 
reaction between animal matters and carbonate of potash, when fused together 
at a red heat, which gives rise to that salt, it is necessary to keep in mind the 
following properties of the salt: — When heated to redness in a close vessel, 
ferrocyanide of potassium is decomposed into cyanide of potassium, carburet 
of iron and nitrogen gas; that, is, looking upon the ferrocyanide of potassium 
as a double cyanide, the cyanide of iron is converted into carburet of iron and 
nitrogen gas, while the cyanide of potassium escapes decomposition. The 
cyanides of metals in general which can combine with carbon, are decom- 
posed in the same way as the cyanide of iron; thus the cyanide of silver when 
heated gives at first a little cyanogen, but afterwards it fuses, and glowing 
suddenly, gives nitrogen gas, the carbon remaining in combination with the sil- 
ver. The addition of carbonate of potash to the heated ferrocyanide of potassium 
prevents the decomposition of any cyanogen, (page 319 note,) cyanide of po- 
tassium being then formed, together with oxide of iron; and when charcoal 
forms a third ingredient of the fused mixture, the oxide of iron is reduced to 
the metallic state. Hence ferrocyanide of potassium cannot be supposed 
ready formed in the red-hot mixture of the iron pot in which it is manufac- 
tured, that mixture containing both charcoal and carbonate of potash. 

In the manufacture of this salt, animal substances, such as dried blood, horn, 
hoofs, and bristles; with common pearlashes, are the materials employed. 
The animal matter is used either in its natural state, or it is previously sub- 

56* 



666 CYANOGEN. 

mitted to distillation, as in the preparation of ammonia, and the residual char- 
coal merely employed for the manufacture of the prussiate. The projection 
of animal matter into the melted potash occasions a lively effervescence, from 
the evolution of carbonic acid and some combustible gases. The liquid is 
stirred after each addition of the materials. The usual proportions employed 
are equal parts of pearlashes and animal matter, or ten parts of the former and 
eight parts of carbonized animal matter. Three or four per cent, of iron 
filings are usually added to the mixture. After each addition of animal matter 
the heat is urged until the whole is fused, and the melted material, which is 
of a thick consistence, is not removed from the pot until the charcoal is seen 
to be equally diffused through the whole mass. The mass, after cooling, is 
placed in an iron pan filled with water, the clear liquid after a time drawn off, 
and water boiled several times on the insoluble residue. The liquids are 
evaporated for crystallizing the salt at a temperature not exceeding 203° Fahr. 
The formation of prussiate takes place after the solution of the melted mass, 
by the action of the matters dissolved upon the insoluble residue; for this 
melted mass yields nothing but cyanide of potassium to alcohol; and contains 
no prussiate. In explanation of the formation of cyanide of potassium in the 
melted mass, it is stated by Liebig that metallic potassium readily produces 
that salt w T hen fused with calcined blood, disengaging at the same time a con- 
siderable quantity of charcoal; the proportion of nitrogen to carbon, in cyano- 
gen, being one equivalent of the first to two of the last, while in blood, hair, 
and horn, the proportion is 1 to 6. Now when these animal matters are fused 
at a high temperature with potash, the free charcoal reduces the potash to the 
state of potassium; the latter then acts upon the azotized carbonaceous matter, 
forming cyanogen, with which it unites. A second mode in which cyanide 
of potassium is produced, is when ammoniacal gas is conducted over a mixture 
of carbonate of potash and charcoal at a red heat. This is accounted for by 
the action of ammonia upon charcoal alone at a red heat; the gas is entirely 
converted into hydrocyanic acid and hydrogen (NH 3 and 2C =?= H,NC 2 and 
211.) Now hydrocyanic acid decomposes carbonate of potash at a red heat, 
forming cyanide of potassium. Hence the product of cyanide of potassium 
is most considerable when the animal matter is used in its natural state, and 
not previously carbonized, a fact of which the manufacturers of prussiate of 
potash have long been aware from experience. To account for the subsequent 
conversion of the cyanide of potassium in the process into prussiate, it is ab- 
solutely necessary that iron exist in the fused mass; but it may indifferently be 
in the condition of metallic iron, the protosulphuret or the protoxide of iron. 
The first is readily dissolved by a solution of cyanide of potassium with evo- 
lution of hydrogen gas (3KCy with HO and Fe = 2KCy ,FeCy and KO and H;) 
the second with the formation of sulphuret of potassium, and the third with 
that of caustic potash. When the iron is added in the state of protosulphate 
to a solution of cyanide of potassium, one third of the latter salt becomes 
cyanide of iron (a brown insoluble matter,) which is dissolved by the other 
two-thirds of the alkaline cyanide, and the ferrocyanide formed. These pro- 
cesses are not altered in the slightest degree by mixing caustic potash or its 
carbonate, or the sulphuret of potassium, with the solution of cyanide of po- 
tassium. Much of the iron necessary is derived from the corrosion of the 
iron pot in which the fusion is conducted.* 

* Liebig; Proceedings of the Chem. Soc* of London, vol. i. p. 2. 



CYANOGEN COMPOUNDS. 667 



HYDROCYANIC ACID. 



Syn. Prussic acid; formula, H-f-Cy. This acid was discovered by Scheele* 
and its constitution first ascertained by Gay-Lussac. It may be obtained an- 
hydrous by transmitting dry sulphuretted hydrogen gas over cyanide of mer- 
cury in powder, and contained in a glass tube; sulphuret of mercury being 
formed, and hydrocyanic acid liberated. The vapour of the latter should be 
carefully condensed, by conducting it into a Liebig's condenser charged with 
ice-cold water. It may also be obtained very conveniently by the following pro- 
cess of M. Trautwein. Fifteen parts of ferrocyanide of potassium (page 318,) 
are distilled in a glass retort, at a very gentle heat, with 9 parts of sulphuric 
acid previously diluted with 9 parts of water and cooled, and the product con- 
ducted into a well cooled condenser, containing 5 parts of chloride of calcium 
in coarse fragments. The distillation is stopped as soon as the salt in the 
condenser is entirely covered by fluid; and the latter is poured off and trans- 
ferred into a bottle with a well ground stopper, and secluded from light. 

Hydrocyanic acid is a colourless liquid, of density 0.6967 at 64°, still 
liquid when free from water at — 64°, boiling at 80°; miscible with water, 
alcohol and ether in all proportions. It consists in the state of vapour of 2 
volumes of cyanogen and 2 volumes of hydrogen united without condensa- 
tion; its combining measure is therefore 4 volumes, like that of all other hy- 
drogen-acids; and its theoretical density 943.7, air being 1000. It has a 
peculiar, very penetrating and suffocating odour, resembling that of the dis- 
tilled water of bitter almonds, its taste is very bitter and burning. Hydrocy- 
anic acid is in the highest degree poisonous, and its vapour when inspired, 
produces immediately fatal effects. Its poisonous action is best counteracted 
by the inhalation of air containing chlorine or ammonia. Hydrocyanic acid 
scarcely reddens litmus; its vapour is very inflammable. When pure it easily 
undergoes decomposition, particularly under the influence of light, ammonia 
being formed with a brown precipitate. This decomposition is prevented by 
a slight admixture of any other acid. When potassium is heated in the va- 
pour of hydrocyanic acid, cyanide of potassium is formed, and the hydrogen 
of the acid is disengaged as gas. When its vapour is passed over ignited 
quicklime or barytes, a mixture of cyanide of the metal and cyanate of its ox- 
ide is formed, and pure hydrogen disengaged. Chlorine decomposes hydro- 
cyanic acid, and forms hydrochloric acid and chloride of cyanogen. 

The aqueous solution of hydrocyanic acid may be prepared by precipitating 
potash from cyanide of potassium, by means of tartaric acid, and may in this 
way be obtained at once of a determinate strength and in a good condition for 
preservation (page 320.) But to prepare this acid in considerable quantity 
the following process may be followed, which is that of Gei<jer with the pro- 
portions modified. Eight parts of ferrocyanide of potassium with 7 parts of 
oil of vitriol diluted with 36 parts of water, are slowly distilled nearly to dry- 
ness, the product being transmitted through a Liebig's condenser, and collected 
in a receiver containing at first 8 parts of water. The condensed liquid con- 
tains very uniformly 1.62 parts of hydrocyanic acid, which corresponds with 
one-half of the quantity of cyanogen in the salt, the other half of the cyanogen 
remaining in the residuary insoluble ferrocyanide; the latter is white or yel- 
lowish-white when pure, but is often coloured by prussian blue. In this re- 
action 2 equivalents of ferrocyanide of potassium are decomposed by 6 equi- 
valents of sulphuric acid, which liberate 3 equivalents of hydrocyanic acid. 
The residuary products are an insoluble ferrocyanide of potassium and iron* 
K,Fe-fFeCy 3 (Everitt,) and 3 equivalents of bisulphate of potash; or; 



668 CYANOGEN COMPOUNDS. 

2(K 2 +FeCy 3 )and 6(HO,S0 3 )=K.Fe + FeCy 3 and 3(HO,S0 3 -f KO,S0 3 ) 

and 3HCy. 

If ferrocyanide of potassium be viewed as a double cyanide of iron and po- 
tassium, FeCy-f-2KCy, then the decomposition in the foregoing process is 
limited to the cyanide of potassium of the salt, of which cyanide 3 atoms are 
decomposed out of the four contained in 2 equivalents of the double salt; and 
the residuary insoluble double cyanide is 2FeCy-fKCy.* 

The proportion of hydrocyanic acid in the acid prepared by the preceding 
process may be ascertained by accurately weighing a portion of it, amounting 
to about 100 grains; adding to this portion nitrate of silver in excess, collecting 
the white insoluble precipitate of cyanide of silver which falls on a weighed 
filter, drying and weighing together precipitate and filter. Five parts of the 
precipitate correspond to 1 part of hydrocyanic acid. Or red oxide of mer- 
cury may be used to test the strength of the aqueous acid. A drop or two of 
caustic potash is added to a weighed quantity of the dilute acid, and then a 
known weight of the red oxide of mercury in fine powder is agitated with it. 
The metallic oxide dissolves readily as cyanide of mercury, every 4 parts of 
oxide dissolved corresponding with 1 of anhydrous acid. The hydrocyanic 
acid may then be reduced to any degree of strength desired, by the addition 
of water. 

The dilute acid, when absolutely pure, soon decomposes, becoming brown 
and then black, but has stability imparted to it by the smallest trace of sul- 
phuric acid; an addition which should be made when it is intended to preserve 
hydrocyanic acid for medical use. The solution has the taste, odour and 
poisonous qualities of the anhydrous acid. 

Hydrocyanic acid may be detected by its odour, or by adding a few drops 
of sulphuric acid to the liquid containing it, and covering the vessel with a 
glass plate having its lower surface moistened by a solution of nitrate of silver. 
The hydrocyanic acid rises from its volatility, and produces a white precipi- 
tate in the nitrate of silver. 

But the most delicate and satisfactory indication of hydrocyanic acid is the 
production of Prussian blue from it, by a process which is known as Scheele's 
test. If the liquid to be examined contains much organic matter, as the con- 
tents of the stomach in a case of poisoning, it is mixed with about one-sixth 
of its bulk of oil of vitriol and distilled. The test is then applied to the dis- 
tilled liquid. 

1. A few drops of protosnlphate of iron are added to the liquid to be tested, 
with a slight excess of caustic potash so as to precipitate the oxide of iron. 

2. The alkaline liquid, after a few minutes' exposure to air, to allow of the 
formation of some peroxide of iron, is made acid by the addition of hydro- 
chloric acid, when Prussian blue is formed and precipitates. 

Hydrocyanic acid does not decompose carbonates, and may therefore be 
purified from other acids by distilling it from chalk. But the acid so distilled 
cannot be preserved without adding a trace of a mineral acid to it. 

[* A more economical process is to convert the ferrocyanide into impure cyanide, (page 
819, note,) previous to decomposing it by sulphuric acid. The product is more abundant, 
five atoms of ferrocyanide yields by sulphuric acid only eighteen atoms of hydrocyanic 
acid, while if previously converted into cyanide it will produce twenty-five atoms, and in 
addition the distillation is conducted with more facility. Equal parts of sulphuric acid 
and cyanide of potassium are the best proportions ; the cyanide to be dissolved in its own 
weight and the sulphuric acid to be diluted with three times its weight of water, and 
gradually added to the ?olution of the cyanide. Liebig, Journ.de Ph. andChim. and Am. 
Journ. of Pharm., January, 1843. R. B.] 



669 

Cyanides.— Hydrocyanic acid forms a metallic cyanide and water with red 
oxide of mercury, oxide of silver and other metallic oxides of which the metal 
has a feeble affinity for oxygen. The cyanides of these metals are not de- 
composed by dilute oxygen-acids, and resist for a long time the action of con- 
centrated and boiling nitric acid. But the same cyanides are decomposed very 
easily by sulphuretted hydrogen and hydrochloric acid. The cyanide of mer- 
cury is resolved when heated into metal and cyanogen, a portion of the latter 
remaining in the retort as paracyanogen, a black coaly matter, isomeric with 
cyanogen. Caustic potash is not neutralized by hydrocyanic acid, but re- 
mains strongly alkaline, while the solution retains the odour of the acid. 
Hence it is doubted whether cyanide of potassium is then formed, and rather 
supposed that hydrocyanic acid unites directly with oxide of potassium. But 
the solid cyanide of potassium, when dissolved in water, has the same cha- 
racters as the preceding solution. Cyanide of potassium dissolves the metallic 
cyanides insoluble in water, forming double salts, and then acquires stability. 
Cyanide of potassium is decomposed when heated with a solution of caustic 
potash; the cyanogen of the former salt, uniting with the elements of water, 
is converted into formic acid and ammonia: 

K,NC 2 and 4HO=KO-f C 2 H0 3 and NH 3 . 

The insoluble cyanides of all the non-alkaline metals may be obtained by 
adding hydrocyanic acid to an acetate of the metal. 



DOUBLE CYANIDES. 

The soluble cyanides of potassium and sodium dissolve all the insoluble 
cyanides of the metals proper, and form double compounds, generally crys- 
tallizable, which are not decomposed or modified by alkaline carbonates nor 
metallic chlorides. 

Protncyanide of iron, FeCy, with certain other cyanides, comports itself in 
a peculiar manner with other metallic cyanides and also with hydrocyanic 
acid. The cyanide named in combination with two equivalents of cyanide of 
potassium, FeCy-f 2KCy, forms a neutral salt, ferrocyanide of potassium, 
(page 318,) which is not poisonous, gives no hydrocyanic acid with sulphuric 
acid at the ordinary temperature, while its iron is not precipitated by an alkali 
or alkaline carbonate; for in this compound the properties of both a cyanide 
and salt of iron entirely disappear. If .the potash of this double salt is preci- 
pitated by tartaric acid, a new double cyanide is formed, highly acid and crys- 
tallizable, containing protocyanide of iron with 2 equivalents of hydrocyanic 
acid, FeCy-f 2HCy, known as f err o cyanic acid, oy ferrocyanide of hydrogen. 
On the view of the constitution of these salts proposed by M. Liebig, they 
contain a bibasic salt-radical ferrocyanogen FeCy 3 . in combination, with 2K 
in the first, and with 2H in the second. Ferrocyanide of lead, 2Pb,FeCy 3 , 
is a white precipitate with a shade of yellow, formed on adding ferrocyanide 
of potassium to a salt of lead. Ferrocyanide of copper, Cu 2 ,FeCy 3 , a reddish- 
brown precipitate, insoluble in dilute acids, formed on adding ferrocyanide of 
potassium to a salt of black oxide of copper. Sesquiferrocyanide of iron or 
Prussia?! blue, Fe 4 ,3FeCy,, is precipitated on adding the same soluble ferro- 
cyanide to a persalt of iron (page 393.) With a protosalt of iron, a geeenish- 
white precipitate is produced, which according to Berzelius, is a double ferro- 
cyanide of potassium and iron, K.Fe 3 ,2FeCy 3 (page 388.) 

Sesquicyanide of iron, Fe 2 Cy 3 , in combination with other cyanides, forms 



670 CYANOGEN COMPOUNDS. 

another class of compounds, analogous to the preceding. With 3 equivalents 
of cyanide of potassium, (Fe 2 Cy 3 + 3KCy,) it forms the red prussiate of pot- 
ash, or ferricyanide of potassium, K 3 ,Fe 2 Cy 6 (page 319.) With 3 equiva- 
lents of hydrocyanic acid, Fe 2 Cy 3 -f-3HCfy, it forms ferricyanic acid or ferri- 
cyanide of hydrogen, H 3 ,Fe 2 Cy 6 ; it is obtained by decomposing the insoluble 
ferricyanide of lead by sulphuretted hydrogen. The ferricyanide of potassium 
produces with a protosalt of iron, ferricyanide of iron, Fe 3 ,Fe 2 Cy 6 , a beauti- 
ful variety of Prussian blue (page 388.) The same alkaline ferricyanide does 
not disturb a persalt of iron. 

Sesquicyanide of cobalt, Co 2 Cy 3 , forms with other cyanides a class of 
double salts strictly analogous to the immediately preceding class, and which 
are represented as compounds of a tribasic salt-radical, cobalticyanogen, Co 2 
Cy 3 , or as cobalticyanides. Cobalti cyanide of potassium, K 3 ,Co 2 Cy 3 was dis- 
covered by L. Gmelin, and is prepared by heating slightly a mixture of pro- 
toxide of cobalt, or its carbonate, with a solution of potash supersaturated with 
hydrocyanic acid ; hydrogen is disengaged with a slight effervescence, and the 
solution when evaporated, furnishes the salt in question in reddish-yellow crys- 
tals, which require to be purified by a second crystallization. It is isomorphous 
with ferricyanide of potassium. 

Sesquicyanide of manganese, Mn 2 Cy 3 , appears also to form with other 
cyanides a similar class of salts (page 374.) 

Sesquicyanide of chromium, Cr 2 Cy 3 , appears to exist in a class of double 
cyanides of the same type. 

Chromo cyanide of potassium, K 3 ,Cr 2 Cy 6 , is formed when a mixture of 
hydrated oxide of chromium with a solution of hydrate of potash to which an 
excess of hydrocyanic acid has been added, is allowed to evaporate spontane- 
ously in air. The liquid acquires a reddish-brown colour, and deposits yellow 
crystals, which have a similar form and composition with ferricyanide or 
cobalticyanide of potassium. (Bceckmann.) 

Bicyanide of platinum, PtCy 2 , is considered by Liebig as existing, as a 
radical, in a series of platinum compounds, discovered by M. Doebereiner. 
This salt-radical is monobasic. Platinocyanide of potassium, K,PtCy 2 -f 3HO, 
is formed on exposing to a heat approaching redness a mixture of equal parts 
of platinum sponge and dried ferrocyanide of potassium. A solution of the 
heated mass affords first, when evaporated, crystals of ferrocyanide of potas- 
sium, and then of platinocyanide of potassium. The latter crystallizes in thin 
elongated rhomboidal prisms, which are blue by reflected and yellow by transmit- 
ted light. Its solution does not precipitate nitrate of lead, but nearly all the other 
metallic salts. Plafinocyanic acid or platinocyanide of hydrogen, H,PtCy 2 
is obtained by decomposing the platinocyanide of mercury suspended in water 
by a stream of sulphuretted hydrogen gas. It crystallizes in a confused mass, 
of which the faces reflect a copper lustre ; its solution is strongly acid. 



COMPOUNDS OF CYANOGEN WITH OXYGEN. 

Cyanogen forms the three following isomeric acid compounds with oxygen: 

Cvanic acid . . . HO,Cy O, 
Fulminic acid . . 2HO,Cy 2 2 , 
Cyanuric acid . . 3HO,Cy 3 3 . 

Cyanic acid, HO-f-CyO. This acid is formed when cyanogen gas is dis- 
solved in a solution of caustic potash, or passed over carbonate of potash heated 
to redness ; also when ferrocyanide of potassium in a fine powder is ignited in 



UREA OR NORMAL CVANATE OF AMMONIA. 671 

a shallow iron vessel, with stirring and exposure to air at a low red heat. It 
does not exist except in combination. The hydrated acid was prepared by 
Wcehler by distilling dry cyanuric acid, and collecting the product in a receiver 
surrounded by ice. 

It is a transparent very volatile liquid of a pungent odour, highly corrosive, 
miscible with water. Soon after its preparation this liquid spontaneously 
undergoes a very extraordinary change : it is converted with the evolution of 
heat into a white solid matter, cyamelide, having the same composition in 100 
parts, but insoluble in water and dilute acids, dissolved by caustic alkali, with 
the formation of ammonia, a cyanate and cyanurate of the alkali. The pro- 
bable formula of cyamelide is NH-|-C 2 2 (Lie big.) Cyanic acid in solution 
reddens litmus at first, but is soon transformed into bicarbonate of ammonia, 
by uniting with the elements of 2 atoms of water : 

HO+C 2 NO and 2HO=NH 3 ,C 2 4 . 

Cyanates. — The alkaline cyanates are soluble, all the others are insoluble. 
They are recognised by the decomposition of their acid, which occurs soon 
after it is liberated by another acid. Ammonia forms two compounds with 
cyanic acid ; one which contains more ammonia than belongs to a neutral salt 
is produced when the acid vapour and dry ammoniacal gas are mixed together, 
and forms a white woolly crystalline substance. This cyanate affords ammo- 
nia when treated by an alkali, and its acid undergoes the usual decomposition 
when liberated by another acid. But if heated, either dry or in solution, it 
loses a little ammonia, still retaining, however, the elements of a neutral cyanate, 
and is transformed into urea, a change the more remarkable that urea is a sub- 
stance belonging to the animal economy. 

Urea or anormal cyanate if ammonia, C 2 2 N 2 H l =C 2 2 -f 2NH 2 (Dumas.) 
This substance, discovered by Vauquelin and Fourcroy in urine, was obtained 
from cyanic acid and ammonia by Wcehler, and is the first peculiarly organic 
product which was formed artificially. It exists in the form of lactate of urea 
in human urine, and combined with hippuric acid in the urine of the cow and 
elephant (Cap and Henry.) Urea combines with most acids without neutrali- 
zing them, and is a feeble base. 

The following is an advantageous process for urea from human urine, with- 
out the use of alcohol. Fresh urine is evaporated in a water-bath to about ^ 
or J f of it volume, allowed to cool and filtered. Oxalic acid is taken in the pro- 
portion of about half an ounce to each pint of urine employed, dissolved in twice 
its weight of hot water, and the solution slowly added with continual agitation 
to the concentrated urine ; a large production of a buff-coloured precipitate re- 
sults, which is oxalate of urea. The impure oxalate, when quite cold, is col- 
lected on a large calico filter, slightly washed with a cold solution of oxalic 
acid, and pressed in the hands as strongly as possible, to get rid of the mother 
liquor containing salts, &c. This solid mass of oxalate of urea is next dissolved 
in hot water in a capacious vessel, and neutralized with chalk (whiting) rubbed 
up with water to a thick cream. So soon as the acid reaction to test-paper 
ceases, the whole may be thrown on a filter to drain, and squeezed to avoid 
unnecessary loss. On digesting the solution with animal charcoal, again filter- 
ing and concentrating, without ebullition, to a small bulk, crystals of urea are 
deposited on cooling ; these have a brownish colour and disagreeable smell, but 
by a second solution in warm water, with the addition of a little more bone- 
black and filtration, the substance is obtained snow-white and inodorous. The 
urea obtained in this manner burns without sensible ash, and its solution is not 
troubled by a salt of lime. In the latter part of the evaporation of the first im- 



672 CYANOGEN COMPOUNDS. 

pure solution of urea filtered from the oxalate of lime, insoluble oxalate of lime 
separates in crusts upon the surface, which must be removed by filtration. 

Or, nitrate of urea may be formed by adding to the concentrated urine in a 
shallow basin an equal bulk of nitric acid of 1.42, taking care by the gradual 
mixing of the acid and placing the basin in cold water, to prevent any consi- 
derable elevation of temperature. This precaution is necessary, for the urine 
contains chlorides, which when decomposed by the action of nitric acid and 
heat, produce chlorine and nitrous acid, bodies which react injuriously upon 
urea. The impure nitrate of urea which crystallizes is washed several times 
with dilute nitric acid, and then dried by placing it upon a clean porous brick 
or tile, which imbibes the acid liquor. It is redissolved and discoloured by 
means of animal charcoal, crystallized again, and the solution of colourless ni- 
trate of urea treated with carbonate of barytes or carbonate of potash till per- 
fectly neutralized. The nitrate of barytes or nitrate of potash crystallizes 
first from the concentrated solution at a low temperature, and the urea after- 
wards from the mother liquor of those crystals. The urea may be purified 
from any adhering salt by solution in alcohol and crystallization from that 
liquid. 

Urea may also be prepared in large quantity by decomposing the insoluble 
cyanate of lead with ammonia or its carbonate. 

Urea crystallizes in colourless, flattened, four-sided prisms, is soluble in its 
own weight of cold water, in 4 or 5 parts of cold alcohol, and in 2 parts of boil- 
ing alcohol ; it fuses at 248°. 

The taste of its aqueous solution is cooling, like that of nitre, acrid and bitter. 
It is persistent in dry air, but deliquesces in damp air. At a high temperature 
it undergoes decomposition and produces ammonia, cyanate of ammonia, and 
solid cyanuric acid. Alkalies give no indication of ammonia, in a cold solution 
of urea, nor is cyanic acid precipitated from it by the metallic salts. The latter 
acid, however, is revived when a solution of urea is evaporated with nitrate of 
silver, cyanate of silver being deposited in a crystalline state, and nitrate of am- 
monia remains in solution. When urea is dissolved in fused potash or in con- 
centrated and boiling sulphuric acid it assumes the elements of 2 atoms of water, 
and is converted into carbonic acid and ammonia. 

Nitrate of urea is soluble in 8 parts of cold water. It consists of single equi- 
valents of urea, nitric acid and water. (Regnault.) 

Oxalate of urea crystallizes in long thin prisms, which are much less soluble 
in water than the nitrate, and have an acid taste. This salt also contains an 
atom of water. From the oxalate of urea, compounds of urea with other acids 
may be obtained, by precipitating the oxalic acid with a neutral salt of lime of the 
other acid, and thus the hippurate, lactate, sulphate, &c. have been formed and 
crystallized by MM. Cap and Henry * 



[* Cyanate of pntassa. This salt may be prepared by fusing the cyanide of potassium 
in a crucible, and adding powdered litharge in small portions at a time. The cyanide of 
potassium (KCy) unites with the oxygen of the oxide of lead, and forms cyanate of potassa 
(KO,CyO) while the lead being reduced to the metallic state is fused into a button. The 
fused mass is cyanate nearly pure, and may be rendered perfectly so by solution in alcohol 
and crystallization. 

Urea may he produced by mixing this salt with sulphate of ammonia dissolved in water, 
and then acting on the tnass by boiling alcohol. The urea formed by the reaction between 
cyanic acid arid ammonia is dissolved out by the alcohol, leaving behind the sulphate of 
potassa, and is deposited in crystals on the cooling of the solution. Liebig Journ.de China, 
et de Phys. and Am. Journ. of Pharm. Jan. 1843, R. B.] 



CYANURIC ACID. 673 



FULMINIC ACID. 

Formula of the acid supposed anhydrous: C 4 N 2 2 =Cy 3 2 . 

Fulminic acid exists in certain fulminating compounds of silver and mercury^ 
discovered by Mr. Howard, but its true nature was first ascertained by Gay- 
Lussac and Liebig. The acid is Dibasic; it undergoes decomposition when se- 
parated from bases by a stronger acid, into hydrocyanic acid and other products. 
Fulminic acid is formed by the action of an excess of nitric acid and alcohol 
upon nitrate of silver or nitrate of suboxide of mercury. A variety of products 
result from the mutual action of nitric acid and alcohol, including nitrous 
acid ; 2 atoms of which with 1 atom of ether are resolved, in contact with oxide 
of silver or mercury, into water and fulminic acid, the last combining with the 
metallic oxide : 

Nitrous ncid. Ether. Fulminic acid. 

N a 6 and C 4 H.O=C 4 N 2 2 and 5HO. 

Fulminate of silver is also immediately formed and precipitated on transmitting 
the vapour of nitrous acid through a saturated solution of nitrate of silver 
in alcohol. 

Fulminates. — The salt of suboxide of mercury is prepared by dissolving 1 
part of mercury in 12 parts of nitric acid of 1.36, by a gentle heat ; then adding 
11 parts of alcohol of 0.848, and heating by a water-bath. A violent reaction 
soon occurs, with the escape of nitrous ether vapour, and precipitation of metallic 
mercury; and soon fulminate of mercury is deposited in white opaque granular 
crystals, which may be washed when cool, and dried at the ordinary tempera- 
ture. This salt crystallizes from boiling water in fine silky needles, and may 
thus be deprived of the free mercury with which it is accompanied. Fulminate 
of mercury detonates violently by percussion, or when rubbed between hard 
bodies ; in the flame of a Candle it deflagrates with a feeble explosion. Mixed 
intimately with 6 times its weight of saltpetre, it forms percussion powder, which 
is introduced in the state of a paste with water, into the copper capsules used with 
fire-arms. Fulminate of silver is prepared like the salt of mercury, but with 
about twice as much alcohol. It detonates even more violently by percussion 
than the salt of mercury, and also by heat. This fulminate is deprived of only 
half its base by an alkali, and a salt formed containing 1 atom of alkali and 1 
atom of oxide of silver as bases. Nitric acid throws down an acid fulminate 
of silver, containing an atom of water as the second base ; it is crystallizable 
and more soluble than the neutral salt. The action of hydrochloric acid upon 
fulminate of silver is attended with the formation of an acid containing chlorine, 
chlorocyanhy trie acid t of which the probable composition is H 3 -f C 2 NC1 5 (Gay- 
Lussac and Liebig.) 



CYANURIC ACID. 

Formula of the acid crystallized from water: 3HO,Cy 3 3 -f4HO. 

Cyanuric acid was discovered by Scheele and examined by Serullas, but its 

true constitution was first ascertained by Liebig and Washier. It is formed in 

a variety of circumstances ; in the decomposition of urea by heat, the distillation 

of uric acid, in the decomposition of the solid chloride of cyanogen by heat, &c, 

57 



674 CYANOGEN COMPOUNDS. 

M. Liebig recommends its preparation from Melam. A portion of melam is 
gently warmed in a little strong sulphuric acid until dissolved ; the acid liquid 
is poured into about 30 parts of water, and boiled in a flask, with the occasional 
addition of water for four or five days, till the liquid no longer gives a precipi- 
tate of ammelide with ammonia. By evaporation the fluid gives brown crys- 
tals of cyanuric acid, which may be made colourless by repeated crystallization, 
or when this fails by dissolving in concentrated sulphuric acid and precipitating 
by water. The white precipitate by water gives colourless crystals of cyanuric 
acid from a solution in boiling water. In this process, melam on dissolving in 
sulphuric acid is transformed into ammonia and ammelide, and the last in con- 
tact with the acid diluted with water is resolved into ammonia and cyanuric 
acid, as expressed in the following equations : 

Melam. Water. Ammeline. Ammonia. 

C 18 N n H 9 and 6HO=C 12 N 9 H 8 6 and 2NH 3 . 

Ammeline. Cyanuric acid. Ammonia. 
C 12 N 9 H 9 6 =C 12 N 6 6 and3NH s . 

Cyanuric acid has a feeble acid taste, is slightly soluble in cold water and 
dissolves in 24 parts of boiling water. The crystals from water are oblique 
prisms of a rhombic base ; they contain 4HO, which they lose in air at the 
ordinary temperature. Cyanuric acid is obtained anhydrous and crystallized, 
from a concentrated and boiling solution in nitric or hydrochloric acid. One 
atom of cyanuric acid is decomposed by dry distillation and resolved into 3 
atoms of hydrated cyanic acid, of which it contains the elements. It dissolves 
with the aid of heat in the concentrated mineral acids, without decomposition, 
but is decomposed by continued boiling with the formation of carbonic acid 
and ammonia. 

Cyanurates. — In these salts the three atoms, of water of the hydrate of cy- 
anuric acid are replaced in whole or in part by metallic oxides. They are all 
completely decomposed, and their acid liberated by nitric and hydrochloric acids. 

Gaseous chloride of cyanogen, CyCl, is most conveniently prepared by pass- 
ing chlorine in excess into an aqueoas solution of hydrocyanic acid, and ex- 
pelling the chloride of cyanogen by a gentle heat. It is a gas at the ordinary 
temperature having an insupportable, penetrating odour, and provoking tears. 
At 0° Fahr., it crystallizes in long needles like spiculac of ice. It undergoes a 
metamorphosis if confined liquid in a tube, and deposites the solid isomeric 
chloride of cyanogen (Persoz.) It combines with ammonia, as CyCl-f 2NH 3 . 

Solid chloride of cyanogen, Cy* CI,, corresponds in constitution with cyanuric 
acid ; it is formed when a mixture of dry chlorine and hydrocyanic acid is ex- 
posed to the direct rays of the sun. It is white and sublimes in diaphanous 
needles. When digested in hot water, it is resolved into hydrochloric and cya- 
nuric acids. It combines also with ammonia, as Cy 3 Cl^-f 3NH 3 . 

Bromide of cyanogen, CyBr, crystallizes in cubes, but is gaseous at 59°. 

Iodide of cyanogen, Cyl, forms snowy flocks, white and crystalline, which 
volatalizeat 113°. 



SULHPOCYANOGEN. 

Its formula as it exists in combination is CyS 2 ; or it is the bisulphuret of 
cyanogen. 



MELLON, CYANILIC ACID. 675 

When chlorine is transmitted into a strong solution of sulphocyanide of po- 
tassium, a solid matter of a fine yellow colour is precipitated which was con- 
sidered as sulphocyanogen, but has been shown, by Mr. Parnell, to be different, 
and named meta-sulphocyanogen. Sulphocyanogen, as it exists in the sulpho- 
cyanide has not yet been isolated. 

Hydro sulpha cyanic acid, H-fCyS 2 is obtained by decomposing the basic 
sulphocyanide of lead by dilute sulphuric acid, and completing the decompo- 
sition by sulphuretted hydrogen. It is a colourless liquid of a sour taste, which 
spontaneously resolves itself in air into several products. It has not been ob- 
tained anhydrous. It colours red the solution of a persalt of iron ; it is not 
poisonous. 

Sulphocyanides. — The preparation of sulphocyanide of potassium has already 
been described (page 320.) The neutral sulphocyanide of lead is deposited in 
yellow opaque and brilliant crystals, on mixing concentrated solutions of acetate 
of lead and sulphocyanide of potassium. The basic sulphocyanide, Pb,CyS 2 
-f PbO, on throwing the neutral salt into boiling water, or on adding the tribasic 
acetate of lead to sulphocyanide of potassium. It is a yellowish white crystalline 
powder, insoluble in water. 



PRODUCTS OF THE DECOMPOSITION OF SULPHOCYANOGEN. 

Met asulpho cyanogen, C 12 N 6 S 12 H,0 (Parnell.) This is the yellow sub- 
stance precipitated by the action of chlorine on sulphocyanide of potassium in 
solution, with formation of chloride of potassium. It is also formed by the 
action of nitric acid upon the same salt. Metasulphocyanogen dissolves entirely 
in a solution of caustic potash. An acid added to this solution throws down a 
lemon yellow precipitate, with a small quantity of a black matter, which has 
not been fully examined. The yellow substance is the hydrothiocyanic acid 
of Mr. Parnell, of which the probable formula is C 10 N 5 S 12 H 6 Osi^^Cy-Sj 3 
-f2HO. The neutral thiocyanides contain 4 atoms of metal in the place of 
H 4 , and when insoluble are yellow, while the thiocyanides combined with 
metallic oxides are black.* 

Mellon, C 6 N 4 (page 304.) This is the fixed residue which remains as a 
yellow powder, on heating dry metasulphocyanogen to low redness in a glass 
flask, sulphur and bisulphuret of carbon being volatilized at the same time. It 
was discovered by M. Liebig, who supposed 4 atoms of sulphocyanogen 
(C S N 4 S S ) to be resolved into 1 atom of mellon (C 6 N 4 ) 4 atoms of sulphur 
(4S) and 2 atoms of bisulphuret of carbon (C 2 S 4 .) But Mr. Parnell has ob- 
served the appearance in the decomposition of metasulphocyanogen, of water, 
sulphuretted hydrogen, and hydrosulphocyanic acid, in addition to the products 
above. He supposes three equivalents of metasulphocyanogen to be resolved 
into four of mellon, C 24 N 16 ; two of hydrosulphocyanic acid, S 4 C 4 N 2 H 2 ; four 
of sulphuretted hydrogen H 4 S 4 ; eight of bisulphuret of carbon, C 3 S 16 ; twelve 
of sulphur S 12 , and three of water H 3 3 . 

Mellon is insoluble in water, alcohol, and dilute acids ; is decomposed at a 
bright red heat into three volumes of cyanogen and 1 volume of nitrogen. It 
is a salt-radical, combining directly with potassium, with ignition and formation 
otmellonide of potassium ; with hydrogen it forms hydromellonic acid. 

Cyanilic acid,' C 6 N 3 H 3 6 (Liebig.) Mellon is decomposed by the pro- 
longed action of boiling nitric acid, with disengagement of gas, and the liquid 
yields on evaporation, colourless, anhydrous octohedrons of cyanilic acid, which 
has the same composition as cyanuric acid, and also crystallizes from water 

* Philosoph. Mag. 3rd Series, vol. 17, p. 249. 



676 CYANOGEN COMPOUNDS. 

with 4HO. The nitric acid after its action on mellon contains ammonia ; it is 
the only acid which causes mellon to undergo this transformation. 

Boiling potash ley dissolves mellon with evolution of ammonia and formation 
of a salt in white needles, which has not been sufficiently examined. 

HydrO'persulphocyanic acid, CyS 3 H (Woskresensky ;) a yellow matter in- 
soluble in water, formed when sulphocyanide of potassium heated to fusion is 
exposed to a stream of dry hydrochloric acid. It is soluble in boiling alcohol. 

Melam, C l2 N M H 9 (Liebig,) one of the products of the decomposition by 
heat of sulphocyanide of ammonium. It is most conveniently prepared by 
heating a mixture of dry sulphocyanide of potassium with twice its weight of 
sal-ammoniac in a porcelain basin, above 350° or 400°, by a charcoal chauffer. 
Ammonia, sulphuretted hydrogen and bisulphuret of carbon go off, and melam 
remains mixed with chloride of potassium, from which it may be separated by 
washing with pure water. Melam is a grayish white powder, not crystalline, 
insoluble in water, alcohol, and ether. It is decomposed by heat into mellon 
and ammonia. 

Melamine, C 6 N 6 H 6 (Liebig;) a salifiable base formed by dissolving melam 
in 1 part of hydrate of potash dissolved in 20 parts of water ; the mixture being 
kept in ebullition till the turbid liquor becomes perfectly clear. One atom of 
melam with 2 atoms of water are then resolved into 1 atom of melamine 
and 1 atom of ammeline. Melamine is deposited from the concentrated solu- 
tion on cooling in anhydrous rhomboidal octohedrons, transparent, colourless 
or tinged slightly yellow. It is very slightly soluble in cold water, dissolves to 
a greater extent in boiling water, but its solution is very slowly effected ; it is 
neutral to test paper, insoluble in alcohol and ether. When dry melamine is 
strongly heated, the greater portion of it sublimes without decomposition 
Melamine forms erystaJlizable salts on combining with dilute acids. 

SJmmeline, C 6 N 5 H 5 2 (Liebig.) The alkaline solution above, from which 
melamine crystallizes, still contains ammeline dissolved in caustic potash, from 
Which it is obtained, on neutralizing with acetic acid, as a gelatinous white pre- 
cipitate, this is washed and then redissolved in dilute nitric acid; the solution 
gives by evaporation crystals of pure nitrate of ammeline, from which, dissolved 
in water, pure ammeline is precipitated by carbonate of ammonia. It may also 
be obtained by dissolving melam in dilute and boiling hydrochloric acid. 

Ammeline forms very fine brilliant silky needles; is insoluble in water, alco- 
hol, and ether, but dissolves in caustic alkalies. Ammeline is a feeble base 
and combines only with the more powerful acids. Its salts are crystalline, 
have an acid reaction, and water precipitates ammeline from them. 

Ammelide, C 12 N 9 H 9 6 (Liebig,) is a product of the decomposition of 
melam, melamine, and ammeline by concentrated acids. The solution is 
treated with alcohol, and the precipitate of ammelide washed with cold water. 
It may be purified by solution in nitric acid and precipitation by carbonate of 
ammonia. It is a white powder insoluble in water, alcohol, and ether; solu- 
ble in alkalies and the stronger acids. It forms a crystalline compound with 
nitric acid, which is decomposed by water. When long boiled in dilute nitric 
or sulphuric acid, ammelide is completely decomposed and converted into 
ammonia and cyanuric acid. 

Hydro sulphur eta of cyanogen. — Dry sulphuretted hydrogen and cyanogen 
do not combine when mixed together over mercury, but if a drop of water is 
added, the gases are condensed in the water, which affords 'thin yellow crys- 
tals by evaporation, observed by Gay-Lussac, of which the composition is 
C 4 N 2 H 3 S 3 ; or an allantoin, in which the oxygen is replaced by sulphur 
(Vcelckel.) When a stream of sulphuretted hydrogen is conducted into an 
alcoholic solution of cyanogen, the liquid soon becomes yellow, and deposites 
Hue Qrangerred crystals, when artificially cooled, discovered by Wcehler, of 



URIC ACID. 677 

which the composition is CoNHS-f H$; its compound with lead C 2 NHS + 
PbS (Vcelckel.) 

Sulphocyanhydric acid and sulphuretted hydrogen. — A compound acid of 
these acids was obtained by Zeise, as one of the products of the reaction be- 
tween gaseous ammonia and the bisulphuret of carbon in alcohol. Its empi- 
rical formula is CyS 3 H 2 . 



URIC ACID AND THE PRODUCTS OF ITS DECOMPOSITION. 

These form a well-defined class of compounds, which appear from their 
analysis to contain cyanogen and carbonic oxide. M. Liebig connects the 
different members of the class by supposing them to contain a compound radi- 
cal in common, urile, which is itself a combination of 2 atoms of cyanogen 
and 4 atoms of carbonic oxide. Urile, 2Cy-f4CO=C 3 N 2 4 , being indi*> 
cated by Ul, then the compounds are represented by the formulae: — 

Empyrical 
Rationale formulae. formulae. 

2U1+ 1 atom urea =Uric acid =C , N 4 H 4 S 

2Ul + 2 + 4HO =Alloxan = C 8 N„H 4 O l0 

2U1 + +5HO ==Alloxantin = C 8 N^H 5 O l0 

2U1 + 1 atom ammonia-f 2HO = Uramile = C 8 N~ 3 H 5 6 



URIC ACID. 

Formula, G, N 4 H 4 O 6 , or 2U1 + (C 2 2 + 2NH 2 .) An acid which exists 
in the urine of all carnivorous animals, and forms the basis of most urinary 
concretions. It forms in combination with ammonia, the white part of the 
excrement of birds; and vast accumulations of that urate exist in the guano, or 
decomposed excrement of aquatic birds, by which many of the small islands 
on the coast of Peru and Chili are covered, and which is used as manure. 

Uric acid is conveniently prepared from the chalk-like excrement of ser- 
pents. The solid urine of the Boa is reduced to fine powder and added to a 
boiling and very dilute solution of potash, sufficient only for the solution of a 
portion, and ebullition continued until the undissolved mass appears quite 
white. 

The whole is then allowed to cool, thrown upon a calico filter, and washed 
until the water passes off very nearly colourless. The washed white mass, 
which consists of urate of potash, is next dissolved in another portion of caustic 
alkali, filtered, and slowly added to an excess of dilute hydrochloric acid main- 
tained in a state of ebullition. The uric acid which precipitates, may be 
washed first by decantation, and afterwards more completely on a filter, and 
is obtained perfectly white. From the brown liquid filtered from the urate of 
potash, an additional quantity of uric acid may be obtained by supersaturation 
with hydrochloric acid, but the product has a brownish colour. 

Uric acid crystallizes in thin scales of a silky lustre and brilliant whiteness, 
is inodorous and insipid, loses nothing at 212°. This acid is nearly insolu- * 
ble in cold water, requiring, according to Prout 10,000 parts of water at 60° 
for solution, and but slightly soluble in hot water; its solution has a feeble 
reddening effect upon litmus.. It is insoluble in alcohol and ether. It dis- 
solves in concentrated sulphuric acid, and is again thrown down on dilution 
with water. It is also more soluble in concentrated hydrochloric acid than in 
water. In nitric acid, uric acid dissolves with lively effervescence, the gases 

57* 



678 CYANOGEN COMPOUNDS. 

disengaged being carbonic acid and nitrogen in equal volumes. The solution 
contains alloxan, alloxantin, urea, parabanic acid and ammonia. The concen- 
trated liquor becomes of a purple-red (from murexide,) when an excess of 
ammonia is added, affording a character by which uric acid may be recog- 
nised. (Liebig.) 

Urates. — Metallic oxides appear to combine with uric acid without dis- 
placing the basic water of the acid which remains in the salt. The urates 
of the alkalies and alkaline earths are sparingly soluble in cold but more 
freely soluble in boiling water. Urate of ammonia dissolves, according to Dr. 
Prout, in 480 parts of water at 60°. Urate of potash forms crystalline scales 
soluble in about 500 parts of cold water, but is much more soluble in boiling 
water, especially if there be an excess of alkali present. All the urates are 
decomposed by acetic acid. Urate of soda forms the principal constituent of 
gouty concretions. 



ALLANTOIC. 

Formula: C 4 N 2 H 3 3 , or Cy,,+3HO (Liebig and Wcjhler.) This is a 
crystalline substance found in the allantoic fluid of the cow, and produced 
artificially by boiling uric acid with the puce-coloured oxide (peroxide) of 
lead. It is deposited from the allantoic fluid of the cow when concentrated 
by a gentle heat to one-fourth of its bulk, upon cooling, in crystals, which are 
treated with animal charcoal and obtained perfectly pure. In the artificial 
process for allantoin, 1 part of uric acid is boiled in 2 parts of water, and the 
puce oxide of lead added in small quantities so long as it changes colour. The 
liquid, filtered boiling, and concentrated by evaporation, deposites allantoin 
in crystals, which are purified by repeated crystallizations. In the formation 
of allantoin, 2 atoms of the puce oxide of lead lose the half of their oxygen, 
which, with 3 atoms of water produces 2 atoms of oxalic acid, 1 atom of al- 
lantoin and 1 atom of urea: 

C 4 4 -f-N 2 C 4 =1 at. Urile ? _ . d 

2PbO-f 2 H 3 3 + 1 at. Urea $ "~ 

2 atoms of oxalate of lead -4- 1 at. of allant. -f- 1 at. of urea. 

Allantoin crystallizes in brilliant colourless prisms derived from a rhombo- 
hedron. It is tasteless, neutral to test paper, soluble in 160 parts of cold and 
in less boiling water. It dissolves in nitric acid; the solution is decomposed 
by ebullition, without the disengagement of ruddy fumes. It also dissolves in 
a hot solution of an alkali or alkaline carbonate, and crystallizes from these 
solutions without change. Allantoin contains the elements of anhydrous oxa- 
late of ammonia, minus 3 atoms of water, which explains its conversion by 
boiling alkalies into oxalic acid and ammonia. A solution of allantoin in 
water at the boiling temperature, to which a few drops of ammonia is added, 
gives a white precipitate with nitiate of silver, of which the composition is 
expressed by C 8 N 4 H 5 5 -f- AgO, that is, 2 atoms of allantoin, C 8 N 4 H 6 6 , 
.in which 1 atom of water is replaced by 1 atom of oxide of silver. Allantoin 
has also been named allantoic acid. 



ALLOXAN. 

Formula, C<,N 2 H 4 0, . It is the erythric acid of Brugnatelli, and was 
discovered by Liebig and Wcehler in the decomposition of uric acid. 



ALLOXAN, ALLOXANIC ACID. 679 

They recommend for its preparation, to add uric acid gradually to nitric 
acid of 1.35, by which it is dissolved with effervescence. " The action must 
be gentle, and, if heat be applied, it must be done cautiously. As soon as 
crystals begin to appear in the warm liquid, no more uric acid is added for 
the present, and the whole is allowed to cool, when it becomes semi-solid 
from the separation of crystals of alloxan. The mass is thrown on a funnel 
stopped with a little asbestos, and, when it has ceased to drop, the acid liquor 
remaining in the crystals is carefully displaced by a little ice-cold water. The 
crystals are purified by solution in water, avoiding a strong heat, and by re- 
crystallization. The acid liquid which has drained from the first crystals is 
again treated as above with uric acid, and in this way one portion of nitric 
acid may be made to yield 4 to 5 crops of crystals of alloxan. The mother- 
liquor finally left is not lost but yields a large quantity of parabanic acid, ox- 
alurate of ammonia, or murexide, if properly treated. By this process Gre- 
gory obtains, from 100 parts of uric acid, 65 parts of anhydrous alloxan equal 
to at least 90 of the hydrated crystals." (Turner's Elem. of Chem. by Liebig 
and Gregory.) 

Alloxan crystallizes in large colourless octohedrons of a rhombic base, having 
considerable lustre ; they contain 6 atoms of water and are efflorescent. A 
saturated hot solution gives alloxan on cooling in oblique rhomboidal prisms, 
which are anhydrous. It is very soluble in water, reddens vegetable colours 
and stains the epidermis purple. It is converted by the action of acids into 
alloxanic acid, and when boiled with an alkali, it is transformed into urea and 
mesoxalic acid. The puce oxide of lead changes it, with the aid of heat, into 
urea and carbonate of lead, mixed with some traces of oxalate of lead.' It is 
transformed into alloxantin by sulphuretted hydrogen, by protochloride of tin, 
or by metallic zinc with hydrochloric acid. An excess of ammonia transforms 
it into mycomelinic acid, nitric acid into parabanic acid, sulphuric acid or hydro- 
chloric acid into alloxantin, sulphurous acid and ammonia into thionurate of 
ammonia, alloxantin and ammonia into murexide (Liebig.) 

Alloxanic acid (supposed anhydrous,) C 4 N 2 H0 4 ; is produced by the meta- 
morphosis of alloxan by caustic alkalies. The anhydrous acid contains the 
elements of half an atom of alloxan minus 1 atom of water. 

Mesoxalic add (hydrated,) 4HO-|-C r ,0 9 H; or rather, 2HO-f-C 3 4 , is one 
of the products of boiling a saturated solution of alloxanate of barytes or stron- 
tian. Also, when a solution of alloxan is poured drop by drop into a boiling 
solution of acetate of lead, a granular very heavy precipitate of mesoxalate of 
lead falls, while nothing remains in the acid liquor but the excess of acetate of 
lead and pure urea. Both this and the preceding acid may be separated and 
crystallized, and are powerful acids. 

Mycomedinic arid, C 1 6 N S H 1 qOj , is formed on adding an excess of ammonia 
to a solution of alloxan, and raising the mixture to the boiling point. It is 
almost insoluble in cold water, and is thrown down as a yellow gelatinous pre- 
cipitate, which becomes a yellow porous powder on drying. 

Parabanic acid, 2HO-fC 6 N 2 4 , is one of the products of the decomposition 
of uric acid or alloxan by nitric acid, discovered by Liebig and Woehler. It is 
prepared by dissolving 1 part of uric acid or alloxan in 8 parts of nitric acid of 
ordinary strength, evaporating the liquor to a syrup, and allowing it to crystal- 
lize. 

It forms thin, transparent, six-sided prisms, of a very sour taste, resembling 
that of oxalic acid. It is very soluble in water and does not effloresce in the 
atmosphere nor b)' heat ; it is partially volatile. 

Oxaluric aicd, HO-|-C 6 N 2 H 3 7 , is formed on adding ammonia to a boiling 
solution of parabanic acid, or on supersaturating with ammonia a solution 
recently prepared of uric acid in nitric acid, which yields by evaporation crys- 



680 CYANOGEN COMPOUNDS. 

tals of oxalurate of ammonia. The acid when separated is a brilliant white 
powder, light and crystalline ; its taste is very sour, and it reddens litmus. Its 
aqueous solution is decomposed completely by ebullition, and resolved into 
oxalic acid and oxalate of urea. It is formed by the combination of the ele- 
ments of parabanic acid with 2 atoms of water. The crystallized acid contains 
the elements of 2 atoms of oxalic acid and of 1 atom of urea, and may be con- 
sidered as uric acid in which the urile is replaced by oxalic acid. (Liebig.) 

Thionuric acid, HO-fC 8 N 3 H 5 6 (S 2 6 ,) is a bibasic acid produced by the 
simultaneous action of sulphurous acid and ammonia upon alloxan. Liberated 
from thionurate of lead by sulphuretted hydrogen, it crystallizes in very thin 
needles, is persistent in air, very soluble in water, and has an acid taste. It 
contains the elements of 1 atom of alloxan, 1 atom of ammonia and 2 atoms of 
sulphurous acid. On heating thionuric acid, 2 atoms of oxygen of the alloxan 
re-unite with 2 atoms of sulphurous acid to form sulphuric acid, while the ele- 
ments of urile, ammonia and water combine and give rise to uramile. 

Uramile, C 8 N 3 H 5 6 , is prepared by adding hydrochloric acid to a saturated 
and boiling solution of thionurate of ammonia, till it is strongly acid ; the heat 
is continued till the liquid begins to become turbid ; it is then allowed to cool for 
crystallization. Uramile crystallizes in thin and hard tufts, or presents itself in 
the form of a brilliant white powder, composed of very thin silky needles. It is 
sparingly soluble in hot water, wholly insoluble in cold water, dissolves in am- 
monia and caustic alkalies, and is again precipitated, without alteration by acids. 
A solution of potash and dilute acids boiled upon uramile, convert it into ura- 
milic acid, disengaging ammonia. The ammoniacal solution of uramile becomes 
purple-red in air, and deposits crystalline needles of a green colour and metallic 
lustre. In contact with oxide of mercury or oxide of silver, it is decomposed by 
ebullition, into murexide, and at the same time reduces the oxides to the me- 
tallic state. 

Urarnilic acid, C 16 N 5 H 10 O 15 , is prepared by dissolving thionurate of am- 
monia in cold water, adding to the saturated solution a small quantity of sul- 
phuric acid, and evaporating by a water-bath ; after a time urarnilic acid, is 
deposited in transparent four-sided prisms of a vitreous lustre, or in silky needles. 
It is soluble in 6 or 8 parts of cold water, and in 3 parts of boiling water ; the 
solution is feebly acid. In the formation of urarnilic acid 2 atoms of uramile 
unite with the elements of 3 atoms of water, yielding up at the same time the 
elements of 1 atom of ammonia. 



ALLOXANTIN. ' 

Formula : CgN^jHsOj . Alloxantin was first observed by Dr. Prout among 
the products of the decomposition of uric acid by nitric acid, and more lately pro- 
duced and studied by MM. Liebig and Wcehler. Several processes are given 
by the latter chemists for its preparation. 1. From uric acid. — One part of 
uric acid is boiled with 32 parts of water, and dilute nitric acid added by small 
portions at a time till the uric acid is completely dissolved, and the liquor evapo- 
rated to two-thirds. In the course of a few days, or sometimes a few hours, 
the alloxantin is deposited in crystals, which are purified by new crystalliza- 
tions. 2. From alloxan. — It is produced in large quantity by carrying a stream 
of sulphuretted hydrogen into a solution of alloxan. Sulphur is first deposited, 
and then the whole becomes a thick mass of crystals of alloxantin, which are 
separated from sulphur by solution in boiling water. The alloxantin crystal- 
lizes by evaporation in a state of purity. 3. On exposing a solution of alloxan 



MUREXIDE. • 681 

to the action of the voltaic battery, oxygen is evolved at the zincoid, and allox- 
antin is deposited on the chloroid in crystalline crusts. 

Alloxantin crystallizes in oblique prisms of four sides, which are colourless 
or slightly yellow, hard and easily reduced to powder ; they become red in air 
impregnated with ammonia and acquire a green metallic lustre. They are not 
altered at 2 12°, but at 302° (150° centig.) lose three atoms of water, are sparingly 
soluble in cold water, more soluble in boiling water ; the solution reddens litmus. 
Alloxantin heated in chlorine- water, or in strong nitric acid, is changed into allox- 
an ; with salts of silver, it produces a black precipitate of metallic silver. It is de- 
composed by alkalies ; barytes-water produces in its solution a violet precipitate, 
which is made colourless by heat, and in the end disappears entirely. By the 
action of boiling sulphuric acid, 2 atoms of alloxan are converted, with the con- 
currence of 2 atoms of water, into 1 atom of alloxantin, 3 atoms of oxalic acid, 
2 atoms of ammonia, and 2 atoms of carbonic acid. 

The circumstances of the formation of alloxantin are thus explained by M. 
Liebig. By the action of nitric acid, the urile of the uric acid combines with 1 
atom of oxygen and with the elements of 5 atoms of water, giving rise to 1 
atom of alloxantin and to peroxide of nitrogen, N0 4 , which in contact with 
water is converted into nitrous and nitric acids ; the nitrous acid is decomposed 
with half of the urea set at liberty, while the other half of the urea forms with 
nitric acid, nitrate of urea. In the process again with sulphuretted hydrogen, 
1 atom of oxygen of the alloxan combines with hydrogen from the sulphuretted 
hydrogen to form water which remains in the constitution of the alloxantin; 
the sulphur set free is deposited. 

Products of the decomposition of alloxan! in. — When a stream of sulphuret- 
ted hydrogen is carried into a boiling solution of alloxantin, more sulphur is de- 
posited, and on saturating with ammonia a salt crystallizes in thin colourless 
needles, of which the formula is C 8 N 3 H 7 8 , which is considered a compound 
of a new acid, dialuric acid, with ammonia. This acid is resolved into new 
products when liberated by another acid, one of these products by exposure to 
air and evaporation of the solution of the ammoniacal salt in dilute sulphuric or 
hydrochloric acid, is dimorphous alloxantin, a body having the same composi- 
tion as alloxantin, but a different form. On mingling boiling solutions of sal- 
ammoniac and alloxantin, the mixture becomes suddenly of a purple red colour, 
then gradually loses its colour, becoming turbid, and deposits colourless brilliant 
plates of uramile, which become rose-red on drying. The liquid contains, af- 
ter its decomposition, alloxan and free hydrochloric acid. When a solution of 
alloxantin is heated with caustic ammonia, uramile and mycomelinate of am- 
monia are first formed, but are decomposed into other products by the prolonged 
action of ammonia and air. A recent solution of alloxantin in ammonia gra- 
dually absorbs oxygen from the air, and deposits ciystals of oxalurate of am- 
monia. 

MUREXIDE. 

Formula: C 12 N 5 H 6 8 (Liebig and Wcehler.) This beautiful product of the 
decomposition of uric acid was first described by Dr. Prout, under the name of 
purpurate of ammonia. Murexide may be formed by evaporating a solution of 
uric acid in dilute nitric acid, until the solution acquires a flesh red colour, 
allowing it to cool to 160°, and then treating it with a dilute solution of ammonia, 
till the presence of free ammonia is remarked by the odour ; the liquid is then 
diluted with half its volume of water and allowed to cool. It may also be 
formed by bringing together many of the products of the action of nitric acid on 
uric acid, with ammonia, with or without the presence of atmospheric air. The 



682 CYANOGEN COMPOUNDS. 

following method, proposed by Liebig and slightly modified by Gregory, ap- 
pears to be the easiest and most certain, and also most productive. 

" Seven grains of hydrated alloxan and 4 grains of alloxantin are dissolved 
by boiling in 240 grains of water, and the boiling solution added to 80 grains 
by measure of a cold and strong solution of carbonate of ammonia. This mix- 
ture has precisely the proper temperature, and deposites very fine crystals of 
murexide. The experiment is not so successful on a large scale, probably be- 
cause the liquid, by remaining longer warm, undergoes a partial change. It is 
best to try first a saturated solution in cold water of carbonate of ammonia. If 
it do not yield good crystals, add a little water, and try it again, and so on till a 
solution of the carbonate is obtained, which gives a good result. The difficulty 
is owing to the spontaneous formation of different carbonates by the action of 
water on the carbonate of the shops ; but when a proper solution is obtained, 
the experiment never fails." (Turner's Chem. &c, p. 776.) 

Murexide crystallizes in short four-sided prisms, of which two faces, like the 
upper wings of cantharides, reflect a green metallic lustre. The crystals are 
garnet-red by transmitted light ; their powder is reddish brown, and acquires 
a green lustre under the burnisher. Murexide is but slightly soluble in cold 
water, but colours it of a magnificent purple ; it dissolves, however, readily in 
water at 158°, and crystallizes again on the cooling of its solution ; it is insoluble 
in alcohol, ether, or in water saturated with carbonate of ammonia. But this 
substance cannot be purified or obtained in crystals of large size, by crystal- 
lizing it from boiling water. For on boiling murexide in a small quantity of 
water for the time necessary to dissolve the whole, the ciystals become colourless, 
and upon cooling, a yellow gelatinous matter precipitates. Hence, probably, 
the slight uncertainty which attends even the best process for the preparation 
of this substance. Murexide dissolves in solution of potash, producing a superb 
indigo blue colour, which disappears with the application of heat, ammonia being 
disengaged. All the inorganic acids decompose murexide, precipitating from 
its solution murexan in small brilliant plates. Sulphuretted hydrogen decom- 
poses it immediately into alloxantin, dialuric acid and murexan, while sulphur 
is set free. 

Murexan, C 6 N 2 H 4 5 , was named purpuric acid by Prout. It is formed on 
dissolving murexide with heat in caustic potash, heating till the blue colour dis- 
appears, and then adding an excess of dilute sulphuric acid. It crystallizes in 
colourless plates, which have a silky lustre and are very brilliant, is insoluble in 
water and dilute acids; it dissolves in ammonia and other alkalies, in the cold, 
without neutralizing them. The- properties of murexan closely resemble those 
of uramile. Like uramile, murexan boiled with water, red oxide of mercury 
and a little ammonia, yields murexide. The composition of murexan and ura- 
mile, also, not differing much in 100 parts, Dr. Gregory admits it to be possible 
that these two substances may be essentially the same, 



ORGANIC PROCESSES OF PLANTS AND ANIMALS. 683 



CHAPTER XL 



SECTION I. 

ORGANIC PROCESSES OF PLANTS AND ANIMALS. 

Without describing the structure of the organs of plants and animals, I may- 
state shortly the principal observations which have been made respecting the 
food of plants and animals and the chemical changes which it undergoes in 
the animal economy, with the relation which subsists between plants and ani- 
mals. Besides secreting the lignin and cellulose which form the basis of their 
own solid structure, plants elaborate in their organs various substances desti- 
tute of structure, such as sugar, starch, gum, resins, essences, fat oils, and the 
endless variety of principles which the vegetable kingdom presents to the 
chemist for examination. These principles are either contained in the fluids 
of the plant, or are stored up in particular organs, or are thrown off as excre- 
tions. 

The mode of formation of such principles in the plant and the chemical 
agencies by which one principle is transformed into another, have hitherto 
been very imperfectly traced, owing to the difficulty of the investigation occa- 
sioned both by the minuteness of the mechanism and the obscure nature of the 
decomposing forces which appear to preside in organic changes. These forces, 
so far as we can judge, are chiefly of the catalytic class, the azotized albu- 
minous principles of plants having specially the function of ferments, which 
react generally upon other principles in the same manner, it may be supposed, 
as we observe diastase to operate during the germination of seeds in converting 
their starch into gum and sugar. Nature appears to have produced and placed 
near each principle its peculiar ferment, to effect the conversion of the former 
into new substances at the proper season. But the action of ferments is a 
department of chemistry still in it its infancy. 

Food of Plants. — With the exception of the provision for the first growth 
of the young plant which exists in its seed, the food of plants appear to be 
exclusively inorganic. M. Liebig has ably shown that the /nanus or decayed 
vegetable matter which exists in soils is not absorbed and assimilated by plants — 
the extremely sparing solubility of that substance being manifestly incompa- 
tiable with its absorption in any considerable quantity, while even if humus 
did enter plants, the presumption is that like a solution of gum or sugar ab- 
sorbed by the roots, it would pass through the plants unchanged, and be ex- 
creted by the leaves. The admitted value of humus in soil appears to depend 
almost exclusively upon its decomposition by the atmosphere, which is greatly 
assisted by tillage, and the formation of carbonic acid, which gas dissolved in 
water is taken up by the spongioles of the roots, and supplies the plant with 
carbon. 

The ultimate constituents of all plants are oxygen and hydrogen, carbon, 



684 FOOD OF PLANTS. 

nitrogen, with a small portion of mineral acids and bases in the form of salts; and 
the condition in which the first mentioned substances enter the plant, adopting 
the conclusions of M. Liebig, are all the hydrogen, and most of the oxygen, 
as water, the carbon as carbonic acid and the nitrogen as ammonia* All these 
matters are derived from the atmosphere. 

Water, or its elements in the proportions of water, enters largely into the 
constitution of vegetable matter, forming 50 per cent, of lignin, and an equally- 
large proportion of the other neutral principles, starch, gum, sugar, &c. Cer- 
tain hydrogenated compounds are also found in plants produced by the fixation 
of the hydrogen of water without its oxygen, which are employed by the 
plant for accessory purposes. They form the volatile oils which serve as its 
defence against the ravages of insects; the fixed oils, or fats, which envelope 
the seed, and which serve to develope heat by burning at the period of germi- 
nation; and the wax with which the leaves and fruit are coated to render them 
impermeable to water. 

Carbonic acid is found as a constituent of air in a proportion varying from 
4 to 6 lO.OOOths, of its volume. Small as this quantity appears it is shown 
to exceed considerably in amount the whole carbon existing both in living ve- 
getables and in the fossil state as mineral coal. The variation in the propor- 
tion of carbonic acid by night and by day, in winter and in summer is rightly 
judged by M. Dumas to be a simple meteorological phenomenon, depending 
upon this gas being brought down in rain, and absorbed and retained in largest 
proportion by water in the cold season. The gas is directly absorbed from the 
atmosphere by the leaves, and also from the humid soil by the roots of plants. 
Boussingault observed vine leaves in a glass vessel to absorb completely the 
carbonic acid from the air as fast as it was carried to them, however rapid the 
current through the vessel. M. Boncherie has also observed enormous quan- 
tities of carbonic acid to escape from the trunk of a tree cut when in full sap, 
evidently aspired from the soil by the roots. Under the deoxidating influence 
of light, plants decompose carbonic acid retaining its carbon for their own use, 
and returning its oxygen to the atmosphere. Their green leaves absorb the 
chemical rays of the sun so completely, as to give no image in the Daguerreo- 
type. Plants thus possess energetic means of reduction which connot be imi- 
tated, for chemists are ignorant of any method of decomposing carbonic acid 
in the cold. Plants, however, also exhale carbonic acid, particularly in the 
absence of light, and this has been supposed analogous to the expiration of 
carbonic acid by animals, and depending upon the respiration of plants. M. 
Liebig, however, looks upon this exhalation as entirely physical, as the escape 
by diffusion into air of the carbonic acid dissolved in the fluids of the plant, in 
the absence of the reducing light; the carbonic acid being derived bv the roots 
from decomposing humus, and this exhalation most considerable from plants 
growing in a rich soil. Thus, at night, plants allow the carbonic acid to pass 
through them, without absorbing it. 

Ammonia also finds its way into the atmosphere, being a product of the 
putrefactive decomposition of all azotized bodies, and is evolved from them 
principally in the condition of the volatile carbonate. The existence, however, 
of this substance in the air must be transient, as from its solubility in water, it 
will be brought down to the earth by every shower. It thus enters the plant 
by its roots. Another source of ammonia is animal manure, particularly urine, 
Which in a putrid state is rich in salts of ammonia. There can be little doubt 
that nitrogen, in the form of nitric acid, can also be assimilated by plants, as 
appears by the favourable action of nitrate of soda, nitrate of ammonia, and 
other nitrates upon vegetation. 

According to the observations of M. Boussingault, the Jerusalem artichoke 
and leguminous plants generally can assimilate the free nitrogen of the atmos- 



FOOD OF PLANTS, OF ANIMALS. 685 

phere, to a small extent, but the cereals and other plants are entirely destitute 
of that power.* The quantity of nitric acid or nitrate of ammonia produced in 
the atmosphere by lightning, must be utterly insignificant, although some im- 
portance has been assigned to this as a source of the azotized food of plants. 

Of the fixed earthy and saline constituent of plants which are derived from 
the soil, and are found in their ashes wiien burnt none is more generally neces- 
sary than the silicate of potash, which is produced in most soils by the gradual 
decomposition, under atmospheric influences of the felspathic minerals they con- 
tain, or is added in the form of the ashes of burnt wood and plants. Earthy 
phosphates are quite essential to the cereals, and are added tothe'soilin animal 
manure ; hence the constant remark that the cereals, like the domestic animals, 
naturally follow man in his migrations. 

The vegetable kingdom is undoubtedly the great laboratory in which organic 
substances are produced, for from the substances enumerated, water, carbonic 
acid and ammonia, and not from any store of original matter in the soil are the 
principles in plants derived. The steps of the conversion of these into the organic 
principles in the organism of the plant escape detection, but the general character 
of vegetable action is of a reducing nature, such as the Sun's light favours, car- 
bonic acid certainly and probably water being decomposed, their carbon and 
hydrogen retained, and their oxygen returned to the atmosphere. 

Food of Animals. — The organic matters produced by plants form the food of 
animals; for animals produce little or no organic matter, but on the contrary 
destroy it. Indeed the character of the chemical action of animals is exceedingly 
well defined, and the reverse of that of plants. The animal frame may be looked 
upon as an apparatus of combustion, in which the reduced hydrogen and carbon 
of plants are again oxidated as in a furnace, and returned to the atmosphere in 
the form of water and carbonic acid. Thus are sustained the animal heat, and 
the powers of locomotion of animals. While carbonic acid and nitrogen in the 
form of salts of ammonia are supplied to the vegetable world. 

Animals require azotised food for their growth, for all the great constituents 
of the animal frame, such as its fibrin, albumen, and casein are azotised matters; 
nothing indeed is found in the soft parts of the body which is not azotised, 
except water and fat, neither of which is organized. For the renewal of these 
parts, a constant supply of azotised food is also necessary. Gum, starch, and 
sugar, which contain no nitrogen, are incapable alone of supporting life for 
any considerable period, and animals fed exclusively upon the latter sub- 
stances eventually succumb with all the appearances of death from starvation. 

Respiration. — But elementary substances of the amylaceous class although 
they afford no element to the body, supply carbon to be burned in respiration, 
consisting as they do of carbon with oxygen and hydrogen in the proportions 
of water. In the lungs of the higher animals, the dark venous blood is ex- 
posed to air through a thin and humid membrane, permeable to oxygen from 
its solubility; that gas is absorbed by the blood, and imparts to it a fine florid 
red colour, and the characters of arterial blood. There is no reason to believe 
that any considerable oxidation occurs in the lungs although the gas is dis- 
solved there by the blood. The latter containing free oxygen is carried by 
the circulation to the extreme capillaries, where the processes of secretion to 
which it contributes are most active, and where it will enter into combination 
in largest quantity. Indeed it has been found by experiment that venous 
blood absorbs oxygen and becomes red and arterial, without producing the 
smallest trace of heat. 

Carbonic acid being formed is carried by the venous blood to the lungs 
where it escapes, at the same time that the blood obtains oxygen from the 

* Ann. de Chim. et de Phys., t. 76, o. 5 and t. 69, 353. 
53 



686 ORGANIC PROCESSES OF PLANTS AND ANIMALS. 

air and is arterialized. From the accurate observations of Professor Magnus 
on the gases of the blood, it appears that blood gives out from one-tenth to 
one-eighth of its bulk of gas when placed in vacuo; that. the gas obtained from 
both arterial and venous blood contains nitrogen, oxygen and carbonic acid; 
but that while the oxygen in venous blood is at most from one-fourth to one- 
fifth of the volume of the carbonic acid, the oxygen in the arterial blood equals 
at least one-third and sometimes almost half of the volume of the carbonic 
acid in the same blood.* The solvent power of the serum of the blood of the 
ox, for carbonic acid was found, by M. Scherer, to be double that of pure 
water; the serum dissolving twice its bulk of carbonic acid, while water dis- 
solves only an equal bulk of that gas, at the usual temperature of the atmo- 
sphere. 

The air of an easy expiration amounts to 15 or 18 cubic inches, and con- 
tains about 3s per cent, of carbonic acid. The air of a deep expiration con- 
tains 6 or 8 per cent, of that gas, and will not support the combustion of a 
candle. According to Mr. Coathupe, the quantity of air which passes through 
the lungs of a man of ordinary size, in twenty-four hours, is 266-| cubic feet, 
of which 20§ cubic feet are changed into carbonic acid.f The quantity of 
carbon thus thrown off daily from the system is considerable, and is found by 
M. Liebig to be in proportion to the animal heat evolved and exercise taken, 
and thus varies considerably in different individuals. The proportion of car- 
bon expired by himself is 85 ounces daily, by a soldier 13rj ounces, by pri- 
soners in close confinement 7 ounces, and by a boy who takes considerable 
exercise 9 ounces. In an experiment made on a large scale, in which the 
quantity of carbon in the food and also in the excrements and urine of 856 
soldiers was ascertained and compared, it was found that the carbon of the 
latter amounted only to one twenty-seventh part of the carbon of the former; 
and consequently twenty-six twenty-sevenths of the whole carbon in the food 
was converted into carbonic acid and discharged by the lungs. 

When the expired air of man and birds is examined, the proportion of oxy- 
gen which has disappeared, has generally been found sensibly the same as 
that of the carbonic acid produced; while it will be remembered that oxygen 
is converted into carbonic acid, by the combustion of carbon, without any 
change of volume. Such should be the result if the oxygen absorbed in respi- 
ration is wholly consumed in oxidating carbon, as it must be when the food is 
purely farinaceous; such articles of diet as starch, sugar and gum containing 
already sufficient oxygen to convert their hydrogen into water, and requiring 
oxygen, therefore, to burn their carbon only. 

According to some observations, upon which reliance may be placed, the 
oxygen which disappears in the respiration of man is always a little more 
than the volume of carbonic acid produced, which would indicate that a part 
of the oxygen is consumed in oxidating other principles beside carbon, such 
as the sulphur and phosphorus which are discharged in an oxidated state in 
the urine; and to a greater extent probably, in oxidating hydrogen, with for- 
mation of water. In the respiration of carnivorous animals, the proportion of 
oxygen which disappears, without being replaced by carbonic acid, is consi- 
derable, according to the observations of Dulong, a fact which may be con- 
nected with the decided excess of hydrogen over oxygen, in the composition 
of their food. Carbonic acid is also exhaled from the skin of man and other 
animals, as well as from the lungs. The question of the absorption of nitro- 
gen from the air, in the respiration of animals, has been finally settled in the 
negative: they are incapable of assimilating that element in a free state. 

* Ann. de Chim. et de Phys., t. 65, p. 182. 
t Phil. Mag. 3rd Ser. v. 14. p. 401. 



RESPIRATION OF ANIMALS- 687 

(Boussingault: Ann. de Chim. &c, lxxi, 113, and 128.) It is certain, how- 
ever, that nitrogen is occasionally exhaled from the lungs, in a sensible quan- 
tity, (Edwards,) and must come from the decomposition of an azotised con- 
stituent of the blood. 

The fat of animals is a provision for the supply of oxidable matter in respi- 
ration, and speedily disappears in the absence of food, without a particle of it 
being discovered in the urine or feces. Fat is most abundant in herbivorous 
animals, because their supply of food from the vegetable kingdom ceases in 
winter, and is a provision for their sustenance during that period; on the con- 
trary, the bodies of carnivorous animals in a state of nature are entirely desti- 
tute of fat. (Liebig.) 

The following theory of respiration or of the action of oxygen upon the 
blood, proposed by MM. Dumas and Boussingault, has a high degree of pro- 
bability. Under the influence of the oxygen absorbed, the soluble matters in 
the blood are supposed to be converted into lactic acid, an acid which has been 
observed in the blood by Mitscherlich, Boutron-Chalard and Fremy. The 
lactic acid itself becomes lactate of soda, and undergoing a true combustion 
from combination with oxygen is converted into carbonate of soda. The last 
salt is decomposed in its turn by a new portion of lactic acid, and the carbonic 
acid set free, with which the venous blood comes charged to the lungs. The 
conversion of farinaceous matters into tactic acid, out of the body, by the 
action of a special ferment, is a fact well understood; and the discharge by the 
urine, of salts of the organic acids, such as tartrates, acetates and citrates, in 
the form of alkaline carbonates, has also long been observed. The large pro- 
duction of lactic acid in the blood, and its conversion by oxidation into car- 
bonic acid may therefore be admitted. 

The oxidation occurring in respiration is quite sufficient to account for the 
animal heat. MM. Dulong and Depretz observed an excess of heat, in their 
experiments upon animals, which was ascribed by them, and by physiologists 
generally, to a calorific power peculiar to the animal and independent of respi- 
ration. But in these experiments it was assumed that an animal placed in a 
calorimeter with cold water, leaves it having exactly the temperature with 
which it entered; a thing absolutely impossible, as is now known. The cool- 
ing of the animal occasioned the excess of heat obtained in their experiments. 

The animal frame appears thus to have eminently the character of an appa- 
ratus of combustion, by which the complex substances which are formed in 
the vegetable world and serve as food to animals, are converted again into 
simpler forms of matter, such as carbonic acid, water and other oxidated pro- 
ducts, which are returned to the atmosphere and to the soil to become again 
the food of plants.* 

Digestion. — The principal constituents of flesh and the animal fluids are 
all azotised substances, namely, fibrin, albumen and casein, the last existing 
in milk and being the basis of cheese. Two very important conclusions have 
lately been drawn respecting the relations of these substances to each other, 
and their origin in the vegetable kingdom. The first is a deduction from the 
analysis of these substances by M. Mulder, which has been repeated and con- 
firmed in the Giessen laboratory, namely, that these three substances are iden- 
tical in composition. 

* "To mount to the summit of Mont-Blanc, a man requires two days of twelve hours. 
During that time he burns on an average 300 grammes (10 ounces and 258 grains avoir- 
dupois) of carbon or the equivalent of hydrogen. If a steam engine were employed to 
carry him there, it would burn from 1000 to 1200 grammes, to do the same work." — 
Leoon &ur la Siatique chimique des etre& organises, professee par M. Dumas. 



688 



ORGANIC PROCESSES OF PLANTS AND ANIMALS. 



The following are the results of M. Mulder's analyses : 

FIBRIN. ALBUMEN. 



CASEIN. 







/■ 


"WS N 








Of eggs. 


Of serum. 




Carbon . . 


. 54.56 


54.48 


54.84 


54.96 


Nitrogen 


. 15.72 


15.70 


15.83 


15.80 


Hydrogen . 


. 6.90 


7.01 


7.09 


7.15 


Oxygen ~) 










Phosphorus I- 


22.82 


22.81 


22.24 


22.09 


Sulphur J 











100. 



100. 



100. 



100. 



The proportion of the carbon to the nitrogen in these substances is that of 8 
equivalents of the former to 1 of the latter. They differ slightly in the minute 
quantity of phosphorus and sulphur with which they are accompanied. They 
all dissolve in concentrated hydrochloric acid, with the aid of heat, and the 
solutions kept for a time at a pretty high temperature, first assume a beautiful 
lilac, and then a rich violet blue colour. At this stage of the decomposition, 
each of the three substances re-acts in the same way with carbonate of ammo- 
nia and other re-agents. With considerably different physical properties, they 
appear to be modifications of a common principle, which Mulder names Protein, 
and expresses by C 40 H 31 N 5 O 12 ; Liebig, by C 48 H 36 N 6 14 . 

The second conclusion is the observation of M. Liebig, that animals draw 
these principles ready formed from the vegetable kingdom, and do not organize 
them. The parallel vegetable principles are vegetable fibrin, a constituent of 
gluten first properly distinguished by Liebig, and gluten itself, vegetable albu- 
men, and legumin, or as it is termed by Liebig, vegetable casein ; the latter two 
being identical, equally in properties as in composition, with animal albumen 
and animal casein. This appears by the following analyses which were exe- 
cuted at Giessen * 

VEGETABLE FIBRIN. 





I. 


II. 


III. 


(Dr. II. Bence Jones.) 


(Dr. Scherer.) 


(Dr. Scherer.) 


Carbon . , 


, 53.83 


54.603 


54.603 


Nitrogen . 


. 15.59 


15.810 


15.810 


Hydrogen 


7.02 ' 


7.302 


7.491 


Oxygen 


) 






Sulphur 


I 23.56 


22.285 


22.096 


Phosphorus J 


100. 








100. 


100. 




VEGETABLE ALBUMEN, 






From rye. 




From gluten of 




(Dr. Jones.) 


From wheat, 


plants. 


Carbon , 


. 54.74 


55.01 


54.85 


Nitrogen . 


. 15.85 


15.92 


15.88 


Hydrogen 


. 7.77 


7.23 


6.98 


Oxygen 


1 






Sulphur 


t 21.64 


21.84 


22.39 


Phosphorus 


J 








100. 


100. 


100. 



Annalen der Chimie unci Pharmacie, xxxix, 129. 



ANIMAL DIGESTION. 689 

LEGUMIN OR VEGETABLE CASEIN. GLUTEN. 

(Dr. Scherer.) (Dr. Jones. > 

Carbon 54.138 5£.22 

Nitrogen 15.672 15.93 

Hydrogen .... 7.156 7.42 

Off"! .... 23.034 21.38 

Sulphur 5 

100. 100. 

The vegetable and corresponding animal principles are also accompanied by 
the same inorganic substances, in small quantity, namely, magnesia, phosphoric 
acid, lime, iron, alkalies and sulphur. They evolve the same fcetid odour when 
heated, and give the same volatile products containing sulphur and phos- 
phorus. 

Animals thus obtain the constituents of their bodies from plants, if herbivorous, 
or from the bodies of other animals, if carnivorous, and merely assimilate 
organic principles without organizing them. For the azotised vegetable princi- 
ples take a new form in the animal organism, without any change in their 
chemical composition. The albumen, fibrin and casein of the animal system 
also admit, from the identity of their ultimate composition, of being readily con- 
verted one into the other, according as each is required in the animal economy. 
Animal digestion comes thus to be deprived of much of its mystery. M. Dumas 
has thus expressed himself, very lately, respecting that process. 

" Digestion is a simple function of absorption. The soluble matters pass into 
the blood, for the most part unaltered ; the insoluble matters arrive in the chyle 
sufficiently divided to be aspired by the orifices of the chyliferous vessels. 
Digestion has evidently for an object to restore to the blood, a matter proper to 
furnish for our respiration the ten or fifteen grammes of carbon or the equivalent 
of hydrogen, which every individual burns per hour, and also to provide the 
gramme of nitrogen, which is exhaled every hour, in part by the lungs and skin, 
as well as by the urine. Thus, amylaceous matters are converted into gum 
and sugar ; the saccharine matters formed are absorbed. The fat matters are 
divided, form an emulsion, and so pass into the vessels, to form afterwards 
deposits, which the blood takes up and burns, when they are required. The 
neutral azotised matters, the fibrin, albumen and casein, first dissolved, then 
precipitated, pass into the chyle highly divided or dissolved anew. 

" An animal, therefore, receives and assimilates almost untouched, the neutral 
azotised matters which he finds ready formed in the animals or plants upon 
which he lives; he receives oily substances which come from the same sources, 
and also amylaceous and saccharine substances of the same origin. These 
three orders of matters, of which the origin is always traceable to the plant, 
divide themselves into products admitting of assimilation ; into fibrin, albumen, 
casein, and oily bodies, which serve to increase or renew the organs ; and into 
combustible products, sugar and the oily bodies, which are consumed in respira- 
tion. An animal thus assimilates, or destroys ready formed organic matters ; it 
creates nothing." 

Although the usual function of plants is to act, under the influence of the solar 
rays, like apparatus of reduction, in which water, carbonic acid and ammonia are 
decomposed, yet in some circumstances, they act differently and more like ani- 
mals. In the germination of the seed, much heat is produced, with the formation 
of carbonic acid and water. The starch of grain in malting is observed to pass 
first into gum, then into sugar, and lastly to disappear, producing carbonic acid. 
Sugar thus seems to be the agent, by means of which plants as well as animals 

58* 



690 * MODIFICATIONS OF PROTEIN. 

develope the heat they require. The fecundation of plants is always accompanied 
by heat, the flowers respiring and producing carbonic acid. They must, there- 
fore, consume carbon; and accordingly we find that the sugar in the stems of 
the sugarcane has entirely disappeared after the flowering and fructification are 
completed. The shot beet, turnip and carrot contain no longer a trace of sugar 
in their roots. The oils accumulated in some seeds appear to serve, like the fat 
of animals, to support this respiration, and to supply the heat, by their combus- 
tion, which plants require at certain periods of their growth, and for the dis- 
charge of certain functions. 

The curious observation has also been made by M. Morren, that certain green 
animalculas found in stagnant water, perform the usual function of the green 
parts of vegetables, decomposing carbonic acid and evolving oxygen, under the 
influence of the light of the sun. The proportion free of oxygen in the water 
is frequently raised, by their action from 80 to 56, or 57, or even to 61 per 
cent, while carbonic acid disappears in a corresponding proportion. It is in 
the enchelide monad, (of Bory,) only, and some other green animalcule© higher 
in the series, that this phenomenon is observed.* 



SECTION IT. 

MODIFICATIONS OF PROTEIN: ALBUMEN, FIBRIN, CASEIN. 

ALBUMEN. 

This substance forms the white of eggs, whence its name, and is the prin- 
cipal constituent of blood; it is also found in many fluid secretions, and in 
nearly all the solids of the animal body. It exists in two conditions, soluble, 
as it is in the animal fluids, and insoluble or coagulated, when heated to 158°. 

Uncoagulated albumen may be prepared by evaporating the clear serum of 
blood, or white of egg, by a heat of 120°, till it dries up and forms a yellowish 
transparent brittle mass, like gum. This is reduced to powder, and washed 
successively with ether and alcohol, which dissolve out the fat, salts and 
other foreign matters in the serum or white of egg. 

Dry albumen first swells up in water, then forms with it a glairy colourless 
fluid, which is nearly tasteless. At 140° the dry albumen begins to lose its 
transparency, and at 142° it changes into a white coherent mass, in which 
the albumen has passed into the insoluble condition. When dissolved in 
water it coagulates at 158°; a very dilute solution, however, does not become 
turbid till it is boiled. Albumen is thrown down from solution, in a coagu- 
lated state, by alcohol, creosote, by acids, particularly nitric acid; by meta- 
phosphoric acid, but not by the other hydrates of phosphoric acid, nor by 
acetic acid. The precipitates with acids are definite compounds of albumen 
with the latter. Coagulated albumen also forms compounds with acids, 
which are insoluble in an excess of the acid, but are soluble in water. Dilute 
hydrochloric acid precipitates albumen, the concentrated acid when heated 
dissolves the coagulum, of a lilac and then of a deep blue colour, as it also 
dissolves fibrin and casein. Albumen is precipitated from its soluble com- 
pounds with acids, by the ferrocyanide of potassium. Coagulated albumen 

t Ann. de Chim. et de Phys. 3 ser. 1. 456. 



FIBRIN. 691 

dissolves in caustic alkalies and neutralizes them; the solutions are precipi- 
tated by soluble metallic salts, and insoluble albuminates of the metals formed. 

A solution of albumen in water is precipitated by acetate of lead, and 
many other metallic solutions. Insoluble compounds are formed, one of 
which is of considerable interest, that of chloride of mercury; as albumen is 
had recourse to as an antidote to corrosive sublimate, the white of one egg 
precipitating about four grains of that salt. To form the albuminate of chlo- 
ride of mercury, a solution of corrosive sublimate is added in excess to a 
solution of albumen, and the white flaky precipitate is collected on a filter and 
washed. It is slightly soluble in water, resembles the curd of milk and is 
insipid; it dissolves in a solution of common salt. Lassaigne finds that when 
heated it coagulates; the albumen appearing to abandon chloride of mercury, 
at the same time, which may afterwards be dissolved out by ether. It con- 
sists, when dried, according to the same chemist, of 93.4 parts of albumen and 
6.6 parts of chloride of mercury, in 100 parts. Chloride of mercury forms a 
similar compound with fresh fibrin. The solution of albumen is also preci- 
pitated by an infusion of nutgalls. 

Soluble albumen dissolves phosphate of lime, a salt, of which about 2 per 
cent, may be separated from coagulated albumen by dilute hydrochloric acid. 
Metallic silver is blackened by albumen, which always contains sulphur, 
whether the albumen is soluble as in the egg and blood, or insoluble as in 
the hair* 



FIBRIN. 

This principle is contained by the living blood in a soluble state, but soon 
coagulates when withdrawn from the blood vessels. It forms the clot of co- 
agulated blood, and constitutes muscular fibre. It is obtained in threads on 
stirring newly drawn blood with a stick; or by pressing the coagulum in a 
small stream of water, till it becomes colourless and consists of soft fibres. It 
is purified by washing it with ether, or warm anhydrous alcohol which dis- 
solves out fat. 

Fibrin affects a remarkable kind of aggregation, the globules of which it is 
composed, attaching themselves to each other by their ends, so as to form 
threads or fibres. In the humid state it possesses the characteristic softness and 
elasticity of the flesh of animals, and contains about three-fourths of its weight 
of water. It may be deprived of this water in dry air, and then becomes a 
hard and brittle substance; but, like flesh, it imbibes water again when moist- 
ened, and recovers its original softness and elasticity. It always leaves, 
like albumen, when burned, a portion of phosphate of lime. 

Fibrin is insoluble in alcohol, ether and water. When boiled for a long time 
in water, particularly under pressure, its nature is altered and it becomes soluble. 
Coagulated albumen comports itself in the same way. Fibrin forms compounds 
with both acids and bases. In concentrated acetic acid it swells up and forms 
a transparent colourless jelly, which dissolves in a considerable quantity of 
boiling water. This solution is precipitated by ferrocyanide of potassium. In 
other concentrated acids fibrin undergoes a- similar change. Fibrin dissolves 
in caustic alkalies and neutralizes them. It is separated from them by acids, 
and precipitated. 

The fibrin of venous blood may be entirely dissolved in a solution of nitrate 
of potash, although not without rubbing in a mortar and digestion in the cold 
for some time. This solution is coagulated by heat, and greatly resembles a 
solution of albumen, (Berzelius, Scherer.) This solubility in nitre is not possessed 



692 PROTEIN. 

by fibrin from the following sources : arterial blood, the "buffy coat," and that 
obtained by stirring blood, nor by fibrin after exposure for some time to the air, 
or fibrin boiled in water for a few minutes, or digested in alcohol. M. Scherer 
observes that, when in the soluble condition, fibrin is a highly altered substance, 
absorbing oxygen readily and emitting carbonic acid ; but after being boiled 
for a few minutes it produces no carbonic acid in an atmosphere of oxygen gas. 
He concludes that fibrin, although always insoluble in pure water, has still an 
uncoagulated and coagulated condition, like albumen ; that it is uncoaglated in 
the clot of venous blood, and when soluble in a solution of nitre ; but coagulated 
as it exists in arterial blood, from the absorption, he supposes, of oxygen, and 
after being boiled for a few minutes, or treated with alcohol. The decomposi- 
tion of peroxide of hydrogen, with evolution of oxygen gas is occasioned, he 
finds, by fresh fibrin from all kinds of blood, but not by boiled fibrin ; nor is the 
decomposition produced, it will be remembered, by coagulated albumen. A 
solution of venous fibrin in nitre, contained in a deep cylindrical jar, allows a 
precipitate in fine flocks to fall, when the jar is open, but not when it is covered 
and access of air prevented. This precipitate is insoluble in the solution of 
nitre, and possesses the properties of arterial fibrin.* 



PROTEIN. 

Formula: C 40 H 31 N 5 O 12 — Pr (Mulder.) When albumen or fibrin is dis- 
solved in a moderately strong solution of caustic potash, and heated to about 
120°, the small portions of phosphorus and sulphur which it contains, are sepa- 
rated in the form of phosphate of potash and sulphuret of potassium; and when 
this solution is saturated with acetic acid, a gelatinous substance precipitates 
which is the same from both fibrin and albumen, and constitutes protein. After 
being washed, protein is still gelatinous, of a grayish colour, and semi-transpa- 
rent. When dried it is yellowish, hard, easily pulverized, tasteless, insoluble in 
water and alcohol. Like albumen and fibrin it is not fusible by heat without 
decomposition. 

Albumen and fibrin may be considered as compounds of protein with sulphur 
and phosphorus in different proportions. Mulder found in fibrin and in the 
albumen of eggs from 0.36 to 0.38 per cent, of free sulphur, with from 0.32 to 
0.43 per cent, of free phosphorus, which quantities of these elements are in the 
proportion of SP|. Tn albumen from the serum of blood, 0.68 per cent, of 
sulphur, and 33 per cent, of phosphorus were found, or S 2 P:|. The composi- 
tion of these substances is thus represented by Mulder: 

Fibrin, and the albumen of eggs . . . 1-OPr-fS Px 
Albumen of serum 10Pr-fS 2 Pi 

The oxides of lead and silver likewise combine with 10 atoms of protein. The 
globulin of blood, vegetable albumen, and the casein of milk, treated with alka- 
lies, in the same way as fibrin and albumen, give also a protein which is identical 
in composition and properties with the foregoing. 

M. Liebig has adopted for protein the formula C v8 H 36 N 6 14 , which is dif- 
ferent from that of Mulder, although equally compatible with the analytical 
results. It gives the composition of protein, per cent. : 

* Scherer, chemisch physiologische Uniersuchungen. Annalen der Chemie, &c, X., 
October, (1841.) 



CASEIN. 693 

Carbon .... . 55.742 

Hydrogen 6.827 

Nitrogen 16.143 

Oxygen 21.288 



100.000. 



M. Dumas represents the composition of protein differently, I am not aware 
upon what authority, assigning to it more oxygen, than Mulder and Liebig. His 
formula is C 48 H 35 N 6 17 ; which is 48 atoms of carbon with the elements of 6 
atoms of ammonia and of 17 atoms of water. The combustion of protein and 
all its compounds is effected with difficulty in the combustion tube ; to burn the 
carbon completely, M. Scherer found it quite necessary to mix chlorate of potash 
with the oxide of copper, or to burn with chromate of lead. 

Protein combines with both acids and bases, and is soluble in all acids when 
highly diluted. In combining with acids it forms new compound acids; with 
sulphuric acid sulpho-proteic acid, Pr-f-S0 3 . It combines also with 2HC1. 
Ch/oroprofeic acid, Pr+Cl0 3 , is formed on passing chlorine gas through a so- 
lution of albumen, and precipitates in white flocks. The same compound is 
formed by the action of chlorine on ammoniacal solutions of casein and fibrin 
(Mulder.) 

Xanthoproteic acid, 2HO+C 34 H 2 4 N 4 Oj 2 (Mulder,) is formed when albumen, 
or any other protein-compound is digested in nitric acid. The albumen, &C., 
dissolve of a yellow colour, with escape of nitrogen gas, and the formation of 
oxalic acid and ammonia. Two atoms of protein, 1 of water, and 2 of nitric 
acid, yielding 3 of oxalic acid, 2 of ammonia and 1 of hydrated xanthoproteic 
acid as represented above. After being washed with boiling water, this acid 
forms a tasteless orange-yellow powder, which combines equally well with acids 
as with bases. The salts containing the last dissolve in water of a dark red 
colour. 

Leucin, C 12 H 12 N0 4 , a substance discovered by Braconnot. When boiled 
with caustic alkali in excess, protein or any protein-compound is completely 
decomposed, and ammonia, carbonic acid, formic acid, and three azotised bodies, 
are formed: leucin, protid and erythroprotid. The alkaline solution is neutral- 
ized with sulphuric acid, poured off from the sulphate of potash which precipi- 
tates, evaporated to dryness, and the mass boiled with alcohol. Erythroprotid, 
is first deposited, as a reddish brown extractiform mass. This substance, as it 
exists in combination with oxide of lead, is expressed by C 13 H 8 N0 5 , Later, 
the leucin separates in a crystalline state. /Vo/?7/,C, 3 H XO 4 , which is a 
yellowish uncrystallizable brittle substance, remains in solution, with formiate 
of potash. The leucin crystallizes in brilliant plates, like cholesterin, is inodor- 
ous and tasteless, arid sublimes unchanged at 338°. It is but slightly soluble 
in water, and still less soluble in alcohol. It is not decomposed by alkalies. It 
combines with one atom of the protohydrate of nitric acid, and becomes nitro- 
leucic acid, which forms crystalline salts containing 1 atom of base, without 
losing its leucin. The same substance is also formed by the digestion of a pro- 
tein-compound in sulphuric acid. 

CASEIN. 

The curd or coagulable portion of milk has been named casein and also 
caseum; it is a principle having considerable analogy to albumen, coagulable by 
rennet but not by a boiling temperature. Sweet milk contains its whole casein 
in solution, with globules of fat in a state of suspension, which last rise to the 
surface in the form of cream, or are separated, by agitation of the milk, in the 



694 CASEIN. 

form of butter. The milk contains also in solution a considerable quantity of 
lactine or sugar of milk (page 515,) to which the casein stands in the relation of 
a ferment. The latter soon begins, probably after being affected like other fer- 
ments by the air, to convert the lactine into lactic acid (page 551.) Milk thus 
spontaneously becomes sour in open vessels, and its casein is at the same time 
coagulated by combining with lactic acid (Fremy.) 

Casein combines with other acids, besides the lactic, and is best prepared 
according to Braconnot, by adding dilute sulphuric acid to skimmed milk ; a 
white coagulum is formed, the sulphate of casein insoluble in water, which may 
be collected and washed upon a filter. It is afterwards digested with carbonate 
of lead, which abstracts the sulphuric acid, and the casein becoming free is dis- 
solved by the water. The solution of casein is evaporated to dryness, the dry 
matter reduced to powder and digested in boiling ether, to dissolve out fat ; the 
residue of casein is afterwards dissolved again in water, and precipitated by the 
addition of alcohol, to separate it from other matters. 

When dry, casein is yellowish like gum, insipid, and does not dissolve again 
readily in water. Its solution is also yellowish and somewhat viscid, and 
smells like boiled milk ; left to itself it putrefies and smells like old cheese. It 
comports itself with re-agents very like albumen ; it is precipitated by acids, 
even by acetic acid which does not affect albumen. The precipitates formed are 
soluble in an excess of their acid, and also, it is said, in alcohol. Like albumen, 
casien exists both in a liquid and solid form. Its coagulation is effected 
by rennet, the inner coat of the calf's stomach, after it is well washed in hot 
water. Skimmed milk placed in contact with a small portion of this membrane, 
or mixed with an infusion of it, and heated to 90° or 100°, is thickened, and 
coagulates so completely that not a trace of the casein remains dissolved in the 
whey. This action of rennet is that of the pepsin it contains, but how the 
latter operates is unknown. Berzelius. observed that 1 part of the membrane, 
washed and dried, placed in 1800 parts of skimmed milk gradually heated up 
to 122°, occasioned complete coagulation. The membrane taken out after- 
wards, washed and dried, was found to have lost 6 per cent, of its weight. The 
coagulum, mixed with the fat or butter, in sweet milk, strongly compressed 
and dried, forms cheese. The fat may be dissolved out of the latter by ether. 

Coagulated casein is insoluble or only very sparingly soluble in water. It 
dissolves easily in dilute warm vinegar and alkalies. Casein always leaves 
behind it, on incineration, a portion of phosphate of lime, which milk contains 
in considerable quantity. Casein contains a little sulphur but no phosphorus, 
in chemical combination. It belongs to the class of protein compounds, and 
may be considered a combination of 10 atoms of protein with 1 atom of sul- 
phur. Its identity with vegetable legumin (page 619) has already been more 
than once adverted to. 

When milk is heated in an open vessel, it soon becomes covered by a pelli- 
cle composed of insoluble matter. M. Scherer finds that the pellicle is formed 
by the absorption of oxygen, and does not appear upon milk heated in an 
atmosphere of carbonic acid. 

Fresh and pure blood-serum, mixed with twice its weight of distilled water, 
and a small quantity of a solution of caustic alkali, soon loses all alkaline re- 
action, and on heating to the boiling point, the coagulation of the albumen no 
longer occurs; but the solution when heated becomes covered by a pellicle, 
like milk. M. Scherer considers this as the conversion of albumen into casein, 
the pellicle agreeing closely in composition and properties with the pellicle from 
heated milk. 

M. Scherer also finds soluble casein, always to leave, when burnt, a highly 
alkaline ash containing much lime, but in the coagulated state to leave a neu- 
tral ash. The solubility of the casein he, therefore, ascribes to its combination 



PEPSIN, GLOBULIN, &C. 695 

with an alkali, and its coagulation to the saturation of that alkali. The acid 
which saturates the alkali appears to be the lactic, produced by the change of 
the su»ar of milk, under exposure to air, when the milk is heated. 



SECTION III. 
PEPSIN, GLOBULIN, HEMATOSIN, GELATIN, CHONDRIN. 

PEPSIN. 

This is a peculiar animal principle secreted by the stomach and present in 
the gastric juice. It is usually prepared by infusing the mucous membrane of 
the fourth stomach of the calf, which is known as rennet, and as obtained from 
this source is distinguished by the power which it possesses to coagulate milk. 
This property the infusion loses when boiled, indicating a relation between 
pepsin and albumen. The infusion, aided with a few drops of hydrochloric 
acid, and kept at 80 or 90°, dissolves completely portions of albumen boiled 
hard, of fibrin or boiled meat, in the course of from 12 to 24 hours. By means 
of this agent the process of animal digestion has been imitated perfectly, out of 
the body, by Eberle, Schwann and other physiologicalinquirers. 

The most precise information we possess respecting the nature and produc- 
tion of pepsin has been obtained by M. Wasmann, who first succeeded in iso- 
lating it; his observations were made upon the mucous membrane of the sto- 
mach of the pig, which greatly resembles that of man.* The organ which 
secretes the gastric juice consists of glands of a particular nature contained in 
the mucous membrane of a portion of the stomach. When this membrane is 
digested in a large quantity of water at from 86° to 95°, without being cut into 
pieces, but after being well washed, water extracts from it a variety of matters 
besides pepsin ; but if this water be removed and fresh water added and the 
digestion continued in the cold, nothing almost dissolves now except pepsin. 
The operation may be continued with new portions of water till the membrane 
enters into putrefaction ; water extracts pepsin at every repetition till at last 
nothing remains but a tissue, from which hydrochloric acid takes up no matter 
capable of dissolving hard boiled albumen. 

The solution of pepsin, thus obtained from the glandular membrane, is colour- 
less, somewhat viscid, and is capable, if rendered acid by hydrochloric acid, of 
dissolving solid albumen very rapidly. It contains besides pepsin a little albu- 
men, which can be separated from the acid solution by ferrocyanide of potas- 
sium, a salt which does not precipitate pepsin, or by heating the solution, if not 
very dilute, to 170°, or 212° without boiling; the coagulated albumen is then 
deposited in flocks, with a little modified casein. The filtered liquid is no 
longer viscid, but preserves the property of dissolving solid albumen with the 
aid of a little hydrochloric acid. When boiled it becomes turbid again, and 
loses entirely the power to dissolve the albumen. For when the coagulated 
flocks are dissolved in acetic acid, they exert no solvent action on hard white of 
egg, even with the concurrence of hydrochloric acid ; the solution of coagu- 
lated pepsin in acetic acid is not precipitated by ferrocyanide of potassium. 

Pepsin thus appears to be a substance sparingly soluble in water. When its 
solution is evaporated to dryness, there remains a brown grayish, viscid mass 
with the odour of glue and having the appearance of an extract. The solu- 
tion of the latter in water is turbid, and still possesses a portion of the charac- 

^Pharmac. centr. Blatt. 1839, p. 349, 353. 



696 pepsin. 

teristic power of pepsin, but greatly reduced. On adding to a fresh solution 
of pepsin 1 or 2 volumes of strong alcohol, the pepsin is precipitated in white 
flocks which may be collected on a filter. The alcoholic liquid filtered, gives on 
evaporation a brown deliquescent residue, which reddens litmus and is entirely 
deprived of digestive powers. 

The precipitate of pepsin forms white flocks, which, upon drying on the filter 
produce a gray compact mass. When moistened with water, it swells up and 
dissolves in a large quantity of water. It dissolves more easily in water aci- 
dulated with acetic or any other acid ; this solution is not disturbed by ferro- 
cyanide of potassium; and possesses in a high degree the power of dissolving 
coagulated albumen. A solution of dried pepsin in pure water is rendered tur- 
bid by ebullition, and loses its solvent power for aliments. 

Many metallic salts precipitate pepsin, although not entirely, from a fresh so- 
lution of the membrane ; such as protosulphate of iron, sulphate of copper, ace- 
tate of lead, chloride of mercury and protochloride of tin. Pepsin may again 
be separated from these precipitates by exposing them suspended in water to a 
stream of sulphuretted hydrogen ; but a portion of the acid of the metallic salt 
remains in combination with the pepsin, forming a compound which has a well 
marked acid reaction on litmus, and possesses the solvent powers of pepsin in 
a high degree. 

Jicetate of pepsin may be obtained by decomposing the precipitate obtained 
with acetate of lead, by means of sulphuretted hydrogen, then evaporating the 
solution of pepsin with caution to a syrupy consistence, and treating it with al- 
cohol. The acetate of pepsin remains undissolved by the alcohol, in the form 
of white flocks, which become a mass, on drying in the air, resembling gum. 
It does not attract humidity, but dissolves easily in water, with an acid reaction. 
A solution of the dried acetate in 60,000 times its weight of water, to which a 
little hydrochloric acid is added, dissolves white of egg in the course of six 
or eight hours. Alkalies appear to destroy the specific solvent power of 
pepsin. 

JHydror.hlomte of pepsin is obtained on precipitating the infusion of the mu- 
cous membrane by chloride of mercury, decomposing the precipitate, after being 
well washed by sulphuretted hydrogen, and mixing the filtered liquid which con- 
tains the pepsin with alcohol, by which the hydrochlorate of pepsin is left un- 
dissolved like the acetate of pepsin. It possesses properties analogous to those 
of the acetate, and its solution in water dissolves coagulated albumen very ra- 
pidly. The alcoholic liquor above possesses no solvent power; when evapo- 
rated to dryness it leaves a residue which resembles an extract of meat. 

In regard to the solvent power of pepsin for coagulated albumen, it was ob- 
served by M. Wasmann that a liquid which contains 1.7 thousand parts of 
acetate of pepsin and 6 drops of hydrochloric acid per ounce, possesses a very 
sensible solvent power, so that it will dissolve a thin slice of coagulated albu- 
men in the course of 6 or 8 hours' digestion. With 12 drops of hydrochloric 
acid per ounce the white of egg is dissolved in 2 hours. A liquid which con- 
tains 5 grain of acetate of pepsin and to which hydrochloric acid and white of 
egg are alternately added, so long as the latter dissolves, is capable of dis- 
solving 210 grains of coagulated white of egg at a temperature between 95° 
and 104°. It would appear, from such experiments, that the hydrochloric 
acid is the true solvent, and that the action of the pepsin is limited to that of 
disposing the white of egg to dissolve in hydrochloric acid. The acid when 
alone dissolves white of egg, by ebullition, as it does under the influence of 
pepsin; from which it follows that pepsin replaces the effect of a high tempe- 
rature which is not possible in the stomach. The same acid with pepsin dis- 
solved blood, fibrin, meat and cheese, while the isolated acid dissolved only an 
insignificant quantity, at the same temperature; but when raised to the boiling 



HEMATOSIN. 697 

point it dissolved nearly as much, and the part dissolved appeared to be of 
the same nature. The epidermis horn, the elastic tissue (such as the fibrous 
membrane of the arteries) do not dissolve in a dilute acid containing pepsin. 

M. Wasmann has remarked that the pepsin of the stomach of the pig is en- 
tirely destitute of the power to coagulate milk, although the pepsin of the 
stomach of the calf possesses it in a very high degree, from which he is led to 
suppose that the power of the latter depends upon a particular modification of 
pepsin, or perhaps upon another substance accompanying it, which ceases to 
be formed when the young animal ceases to be nourished by the milk of its 
mother. 



HEMATOSIN. 

The blood so long as it flows in the veins consists of a clear liquid with 
floating globules observed by the microscope, which in the higher mammife- 
rous animals are lenticular and circular or elliptical in form, of an orange red 
colour, and marked with a colourless spot in the centre, or nucleus. From 
these globules Berzelius derives two of the most characteristic constituents of 
the blood, hematosin and globulin, which are both closely related to albumen. 
The clear liquor of the living blood, on the other hand, is composed of two 
principles already considered, namely fibrin and albumen. 

To prepare hematosin, blood which has been freed from fibrin by stirrino; 
it well, is mixed with 6 times its bulk of a saturated solution of sulphate of 
soda, in which the blood globules are insoluble, and the latter collected on a 
filter. The dark-red gelatinous mass is boiled with alcohol, to which a little 
sulphuric acid has been added. The hematosin is thereby dissolved, while the 
globulin remains in combination with sulphuric acid, as a colourless or gray 
mass. The alcoholic solution while yet hot is mixed with carbonate of ammonia 
and filtered from sulphate of ammonia and some globulin which precipitate. 
The solution is reduced to about l-12th by distillation, whereby the hemato- 
sin remains as an insoluble pulverulent residue. 

Hematosin is of a dark-brown colour, tasteless and insoluble in water, alco- 
hol, and ether. It dissolves of a red colour in alcohol containing either an 
alkali or an acid. In aqueous solutions of the alkalies it dissolves of a dark 
blood-red colour; it is insoluble in hydrochloric acid. When burned it leaves 
behind a notable quantity of peroxide of iron. The analysis of hematosin 
gives: 

Carbon 
Hydrogen . 
Nitrogen 
Oxygen 
Peroxide of iron . 

100,00 

M. Scherer has, however, shown that the oxide of iron is not essential to 
hematosin, nor necessary to the colour of blood. The matter of the blood 
globules after being dried was intimately mixed in a mortar with concentrated 
sulphuric acid, and the mass afterwards diluted with distilled water, and 
allowed to settle. The liquid above was perfectly clear and colourless, and 
contained sulphate of iron. The insoluble blood-mass was washed on a fil- 
ter with water, so long as the washings contained iron. Boiled afterwards 
59 



65.84 


44 


5,37 


22 


10.40 


3 


11.75 


6 


6.64 


1 



698 GLOBULIN. 

in alcohol, the mass coloured the spirit intensely red. On neutralising the 
sulphate of the colouring matter, the compound in solution, with ammonia, 
much albumen fell, which was dried and ignited; it left a white ash, in which 
not a trace of iron could be detected. The blood red solution in alcohol 
therefore contained no iron. 

GLOBULIN. 

This substance is the principal constituent of the blood globules ; it is a por- 
tein compound and closely allied to albumen. But it has not been isolated, 
and little is known respecting it. The sulphate of globulin which remains be- 
hind in the preparation of hematosin, described above, consists of 4 atoms of 
protein, united with 1 atom of sulphuric acid. The nature of the matter form- 
ing the clear nucleus of the globules is still less understood, but it appears more 
like coagulated fibrin than any thing else. 

The matter of the blood globules, or the globulin and hematosin together, 
may be obtained by mixing blood freed from fibrin, with a solution of sulphate 
of soda, in which the matter of the globules is insoluble and precipitates; or by 
draining the serum out of the clot of blood cut into thin slices, upon folds of 
blotting paper, and afterwards mixing the clot with water, in which the matter 
of the blood globules dissolves of a brown-red colour and transparent. It is 
soluble in pure water, insoluble in serum. When its solution is mixed with salts 
of an alkaline base or with sugar, and exposed to air, it becomes of a lively red. 
The solution of the matter of the blood globules may be evaporated at 122° with- 
out losing its solubility ; but when heated it coagulates, before its temperature rises 
to 181°, and precipitates insoluble. Both in its coagulated and soluble state the 
matter of the blood globules exhibits similar effects with reagents as albumen in 
the same conditions. M. Simon has lately maintained that this matter is com- 
posed of casein and hetamosin, but coagulation by heat is not a property of casein. 



GELATIN. 

This is the basis of glue, size, and animal jelly, and is obtained by the action 
of boiling water upon skin, tendons, ligaments, cellular tissue, and serous mem- 
branes. These materials are dissolved almost entirely, by continued digestion 
in boiling water, and the solution forms a jelly on cooling. A substance is 
obtained from the permanent cartilages, by a similar treatment, which also 
gelatinizes, but is not precipitated by tannin, and differs in other respects from 
gelatin; the latter substance was first distinguished, as a peculiar principle, by 
Muiler, and named chondrin. Gelatin is not found in the blood or any of the 
healthy fluids, nor does it exist as such in the solids, but is a product of their 
alteration by boiling water, as dextrin and starch-sugar are products of the 
alteration of starch by the same agent. 

Gelatin is distinguished by its ready solubility in warm water, and property of 
forming a stiff jelly when it cools. As prepared from different materials, gelatin 
differs considerably in viscidity. Its viscidity, as prepared from skins, is inversely 
as their softness and flexibility. The most adhesive of its forms, glue, is prepared 
from the clippings of hides, hoofs and other refuse of the tan-yard. The solu- 
tion is boiled, filtered above 120°, and after evaporation poured into square 
boxes to gelatinize. The jelly fs cut into slices, and when dried in the air upon 
a nett'ng takes the form of the cakes of glue. Glue is dissolved for use by a 
water-bath heat, after being softened by steeping in cold water. Size, which 
is less tenacious and adhesive, is prepared from parchment, fish skin and seve- 
ral animal membranes; ising'ass from the entrails of several species of fish, 



GEIATIN. 699 

particularly the sturgeon. The latter gelatin gives a colourless solution, which 
has no disagreeable taste or odour ; it forms a firm jelly on cooling when dis- 
solved in 100 times its weight of water. 

Gelatin is insoluble in alcohol and ether. When burned it leaves behind a 
small portion of bone-earth. Its solution in water is not precipitated by alum, 
by neutral protosulphate of iron, by either the neutral or basic acetate of lead ; 
all of which precipitate a solution of the chondrin of cartilage. Gelatin is 
readily soluble in diluted acids and alkalies. Its solution in acetic acid is very 
gluey, but does not gelatinize. Gelatin is not precipitated by corrosive subli- 
mate, which throws down albumen. 

Gelatin forms a white compound with tannic acid, t anno gelatin , which is pre- 
cipitated by a strong infusion of gall-nuts, from a solution of gelatin in 5000 
times its weight of water. The white flocks adhere to each on stirring, and form 
a soft tenacious, and elastic mass, which is of the same composition with, and 
has considerable resemblance to leather. The skins of animals are tanned, after 
being cleaned and deprived of the cuticle and hair by lime-water, and allowed 
to enter into a degree of putrefaction to soften them, by submitting them to the 
action of infusion of oak bark, or other astringent vegetable matter, the strength 
of which is gradually increased until a complete combination takes place. The 
tannin is taken up by the skin, of which the weight is considerably increased 
by this treatment. In the tanning of thick sole-leather many months' digestion 
in the tan-pit is required, but the process has of late been considerably shortened 
by slightly heating the infusion of oak-bark by means of steam. The skin is 
greatly altered by its combination with tannic acid, losing its solubility in boiling 
water, and becoming nearly indestructible by atmospheric agencies ; the animal 
matter it contains is no longer suitable for the preparation of prussiate of potash, 
by fusion with an alkali. 

" Tawed leather is made by impregnating the skin duly prepared by washing 
in potash liquor, with a solution of alum and common salt; it is afterwards 
trodden in a mixture of yelk of eggs and water. The alum and salt re-act on 
each other so as to produce sulphate of soda and chloride of aluminum; the 
latter salt combines with the skin. White glove leather is thus prepared. 

" Wash leather is another important manufacture ; in this, the skin, after being 
prepared and softened, is imbued with oil, and afterwards subjected to a weak 
alkaline solution. 

" Curried leather, is made by besmearing the skin, or leather, while yet moist, 
with common oil, which, as the humidity evaporates, penetrates into the pores 
of the skin, giving it a peculiar suppleness, and making it to a considerable 
extent waterproof. As familiar examples of these processes, the thick sole- 
leather for shoes and boots is tanned ; the upper leather is tanned and curried ; 
the white leather for gloves is tawed; and fine Turkey leather is tawed, and 
afterwards slightly tanned." (Aikin's chemical Dictionary, art. Leather, 
quoted in Brande's Manual.) 

Chlorine transmitted through a solution of gelatin throws down a white elastic 
substance in shreds, which smells of chlorous acid, while humid ; it may be 
obtained in a dry state, by careful drying, and is a definite compound of unal- 
tered gelatin with chlorous acid. 

The composition of gelatin has also been examined by M. Scherer. He found 
isinglass, washed with ether to free it from fatty matters, to leave when burned 
0.5 per cent, of earthy ashes. 

Tendons macerated for a short time in cold water, and afterwards boiled 
successively in alcohol and ether, and dried at 212°, left on being burned, 1.6 
per cent, of ashes. The purified tendons, analyzed by combustion with chro- 
mate of lead, gave: 



700 CHONDRIN. 

Carbon. . . . 50.774 

Hydrogen. . . . 7.152 

Nitrogen. . . . 18.320 

Oxygen. . . . 23.754 



100.000 



This result was confirmed on repetition of the analysis. It leads to the follow- 
ing empirical formula for gelatin C 48 H 4l N 15 18 . M. Scherer observes that 
if this formula be doubled, gelatin will contain the elements of 2 atoms of pro- 
tein, with 3 atoms of ammonia, and 7 atoms of oxygen. 

Products of the alteration or decomposition of gelatin. — By long digestion, 
particularly at a temperature considerably above 212°, gelatin loses its power 
of gelatinizing, and when dried by evaporation forms a yellowish gummy mass, 
which dissolves easily in cold water. 

Concentrated sulphuric acid dissolves gelatin, colourless. If the solution is 
diluted with water and boiled for a long time, gelatin sugar is obtained from it, 
on saturating with chalk. 

A concentrated solution of caustic alkali when boiled with gelatin separates 
ammonia from it, and converts it into leucin (page 693,) and gelatin sugar. 
To separate these substances, the alkaline solution is saturated with sulphuric 
acid, after ammonia ceases to escape, evaporated to dryness, and the mass boiled 
with alcohol which dissolves out the leucin and gelatin-sugar. The alcohol being 
distilled off, the residue is washed with small quantities of cold alcohol at a time, 
by which the very soluble leucin is taken up. The residuary gelatin-sugar may 
then be dissolved in a larger quantity of boiling alcohol, and crystallizes by 
spontaneous evaporation. 

Gelatin-sugar or glycicoll, C 8 H 7 N 2 5 +2HG, crystallizes in pretty large 
rhomboidat prisms, is colourless, inodorous, and very sweet. It fuses at 352°, 
but undergoes decomposition; is soluble in 4f parts of water, in 900 parts of 
spirits of wine, and insoluble in ether. The solution is precipitated by no 
metallic salt, nor by tannic acid. But glycicoll combines with oxide of lead, 
when digested upon it, and then loses two atoms of water (Mulder.) 

According to a late analyses by Boussingault, who does not appear, how- 
ever, to have been aware of Mulder's analyses, the composition of glycicoll is 
C 16 H 16 N 4 14 ; of its compound with oxide of silver, C 1<J H 1 ^N 4 G 1 1 - r -4AgO, 
(Ann. 4c Chim., &c. 3 ser. p. 357.) 

Glycicoll dissolves without decomposition, in hot nitric acid; it forms a com- 
bination with that acid, C 8 H 7 N 2 0$-f 2N0 5 4-4HO, which crystallizes in co- 
lourless prisms, and forms double salts with bases. The composition of the 
double salt of lime, which does not deliquesce in air, is CaO,C 8 H 7 N„0, i -j- 
(2CaO,N0 5 .) 



CHONDRIN. 

This variety of gelatin is derived from the permanent cartilages, such as 
those of the ribs, joints, wind pipe and nose, and cartilaginous bones before 
ossification, from the cornea of the eye, and also, according to Muller, from 
bones in a state of caries. Chondrin is slowly dissolved out of these sub- 
stances by boiling water. 

The solution of this substance fixes on cooling, like that of gelatin, and 
when it becomes dry, by evaporation, has the appearance of solid glue. But 
it is not precipitated by tannic acid; on the other hand it gives precipitates with 



HORNY MATTER. 701 

acetic acid, alum, acetate of lead and protosulphate of iron, which do not 
disturb a solution of gelatin. Chondrin leaves behind when burned above 4 
per cent, of bone earth. It appears also, like the protein compounds, to con- 
tain a small portion of sulphur in combination. 

M. Scherer analyzed this substance in its natural state, before it is altered 
by boiling, operating upon the rib-eartilages of young calves and the cornea. 
The cartilage was scraped clean by a knife r then digested in water containing 
some nitrate of potash in solution, to dissolve out albumen, and afterwards 
boiled in alcohol and ether for the extraction of fat. Dried at 212°, it left 
when burned 6.6 per cent, of earthy ashes. The results of an analysis of this 
chondrin and also of that of the cornea were as follows: 



From 

Carbon. 
Hydrogen. . 
Nitrogen. 
Oxygen. 


rib-cartilage, 

50.895- 

6.962 

14.908 

27.235 


From the cornea.. 

49.522 

7.097 

14.399 

28.982 


By calculation. 

50.745 

6.904 

14.692 

27.659 



100.000 100.000 100.000 

From which, M. Scherer deduces the following empyrical formula for 
chondrin, C 48 H 40 N 6 O 20 . Chondrin thus contains the elements of one atom 
of protein, with 4 atoms of water, and 2 atoms of oxygen. 

Middle coat of the arteries. — This is a highly elastic membrane, of a yel- 
lowish white colour. Purified in the same manner as the rib cartilage, and 
dried at 212°, it left when burnt, 1.7 per cent, of ashes. Its analysis gave a 
result considerably different from that of chondrin, namely: 





i. 


n. 


By 


calculation, 


Carbon. 


53.750 


53.393 




53.91 


Hydrogen. . 


7.079 


6.973 




6.96 


Nitrogen. 


15.360 


15.360 




15.60 


Oxygen. 


23.811 


24.274 




23.53 



3 8 



100.000 100.000 100.000 

The matter of the middle coat of arteries is therefore represented by C 48 H 
N 6 16 ; which is equivalent to 1 atom of protein plus 2 atoms of water 
(Scherer.) 

Membranous and compact horny matter.. — This s-ubstance is a product of 
the organism not subject to reabsorption, and differs in that respect from all 
the others yet considered. 

The membranous horny matter constitutes the epidermis-, in particular, or 
outer skin, and also the epithelium in its different modes of formation. The 
scaly epithelium which forms the inner surface of the blood and lymph vessels, 
the inner surface of many mucous and serous sacs, &c. The columnar epi- 
thelium which forms the surface of the intestinal canal, as well as the surface 
of the passages from most glands. The ciliated epithelium which forms the 
surface of the mucous membrane of the organs of respiration, &c. 

The compact horny matter constitutes hair, horn, nails, claws, &c. 

I. M. Scherer' s analysis of membranous horny matter was made upon the 
epidermis of the sole of the foot. It was first thoroughly washed with water, 
then boiled in alcohol and ether. Dried at 212°, and then burnt, it left 1 per 
cent, of earthy ashes. Its composition, by two analyses, was: 

59* 



702 , HORNY MATTER. 

1 2 

Carbon. . 51.036 50.752 

Hydrogen. . 6.801 6.761 

Nitrogen. .. 17.225 17.225 
Oxygen. > ^ 24>Q38 



Sulphur. 



25.261 



100.000 100.000 



II. Compact horny matter. — Hair was cut into small pieces, well washed 
and digested in water, and finally boiled in alcohol and in, ether. Hair of the 
beard, thus treated, and dried at 212°, left 0.72 per cent, of ashes, when 
burned; hair of a blond colour from the head gave 0.3 per cent, of ashes, the 
black hair of a Mexican gave 2 per cent, of ashes. The substance of nails 
after similar preparation, gave 0.5 per cent, of ashes, wool 2 per cent* Horn 
gave 0.7 per cent, of ashes. Each of these substances was several times ana- 
lyzed, and the results from all were similar, proving that they contain the 
same principle. Deducting the ashes, as usual, the results of one analysis of 
each were: 





Hair. 


Horn. 


Nail. 


Wool, 


Carbon. 


50.652 


51.540 


51.089 


50.653 


Hydrogen. 


6.769 


6.799 


6.824 


7.029 


Nitrogen. 


17.936 


17.284 


16.901 


17.710 


Oxygen. ? 
Sulphur, y 


24.643 


24.397 


25.186 


24.608 



100.000 100.000 100.000 100.000 

M. Scherer constructs the following formula to express the results of these 
analyses, and to exhibit the relation in composition of this class of substances 
to protein; compact horny matter, C 48 H 39 N 7 17 . This contains the ele- 
ments of protein plus, 1 atom of ammonia and 3 atoms of oxygen. 

Horn, hair, wool and other horny substances dissolve in the solution of 
caustic alkali, with disengagement of ammonia, and the formation of some 
acetic acid. When the alkaline solution is neutralized by acetic acid, effer- 
vescence occurs from the escape of sulphuretted hydrogen, and a substance 
falls, soluble in an excess of acetic acid, which possesses the properties and 
composition of protein. When the solution is precipitated by successive ad- 
ditions of acetic acid, the last additions give a yellowish-white precipitate, 
which is different from the first. 

Analyses of the protein from hair and of the other substance, gave the fol- 
lowing results: 



Carbon. 
Hydrogen. 
Nitrogen. 
Oxygen. 


Pro 


,ein from hair.. 

55.150 

7.197 

15.727 

21.926 


Other 


substance from hair 

53.516 

7.168 

14.801 

24.515 



100.000 100.000 



From the composition of the latter, it is supposed to be the same as the en- 
veloping membrane of the albumen and inner coat of the lining membrane of 
the egg. 



FEATHERS, PIGMENTUM, SALIVA. 703 

Feathers. — The material of feathers has hitherto been supposed to be of the 
same nature as horn, but M. Scherer finds the composition of the former to 
be different, and to have considerable analogy to the second substance derived 
from hair and horny bodies, as appears by the following analysis: 





Quills. 


By 


calculation 


Carbon. 


. 52.427 




52.457 


Hydrogen. 


. 7.213 




6.958 


Nitrogen. . 


. 17.893 




17.719 


Oxygen 


. 22.467 




22.866 



100.000 100.000 

The composition is calculated, in the second column, from the formula C 4 $ 
H 39 N 7 16 . By which feathers are represented as having 1 atom of oxygen 
less in their composition than horn. 

Pigmentum nigrum of the eye. — This matter, carefully removed by M. 
Scherer from the choroid by means of a hair pencil, in distilled water, was 
strained with the water through linen, to separate portions of membrane; the 
liquid with the black matter in suspension was then evaporated to dryness, 
and the residue boiled in alcohol and ether to purify it. It contains conside- 
rably more carbon than any of the preceding substances, as appears by the 
following analysis: 

Pigmenlurn nigrum. 
Carbon . . . 58.672 
Hvdrogen . . . 5.962 

Nitrogen . . . 13.768 

Oxygen . . . 21.598 



100.000 



SECTION IV. 



SECRETED FLUIDS SUBSERVIENT TO DIGESTION. 

Saliva. — This liquid, which is secreted by the salivary glands, contains 
mucus and very small transparent globules, visible under microscope. It 
leaves, when evaporated, about 1 per cent, of solid matter, consisting of mucus, 
several salts of potash, of which chloride of potassium is the most considera- 
ble, and a peculiar animal substance, which is named salivary matter. The 
latter is soluble in water, not coagulated by boiling nor precipitated by metallic 
salts. In the salivary glands and ducts of the horse and ass, concretions are 
sometimes found, which are principally composed of carbonate and a little 
phosphate of lime. The saliva of man and the sheep generally contains a 
trace of sulphocyanide of potassium; the saliva of the sheep contains also so 
much carbonate of soda as to effervesce with an acid. 

Gastric juice. — The principal constituent of this fluid is the peculiar princi- 
ple, pepsin (page 695.) When collected from the stomach during fasting, it 
is a transparent fluid, of a saline taste, which is neutral, but during the process 
of digestion it is distinctly acid from the presence of hydrochloric acid. 



704 SECRETED FLUIDS SUBSERVIENT TO DIGESTION. 

Pancreatic juice. — This fluid, secreted in the pancreas, is thrown into the 
duodenum, or the portion of the small intestines nearest the stomach, where 
it mixes with the partially digested food or chyme, as the latter leaves the sto- 
mach. It contains albumen in solution and also a matter like casein; its salts 
are nearly the same as those of the saliva; it has a distinct acid reaction. The 
uses of this fluid in digestion are unknown. 



BILE AND BILIARY CONCRETIONS. 

The bile which is contained in the gall-bladder is conveyed to the duodenum 
and added to the chyme in digestion. It is a greenish-yellow fluid, of a pecu- 
liar sickening odour, and taste which is at first sweet, but afterwards bitter 
and exceedingly nauseous. It contains a great variety of substances, of which 
the most peculiar, which are all in a state of true solution, are bilin, fellinic 
acid, cholinic acid and biliverdin, according to the* latest examination of this 
secretion, by Berzelius. Besides the acids mentioned, it contains oily acids 
combined in common with the others with soda, and several other fatty bodies, 
together with chloresterin. To which are to be added mucus, an undeter- 
mined animal matter, common salt, and the other usual salts of animal fluids. 
The separation of so many substances is extremely difficult, and the more so 
that the constituents of bile are remarkably prone to assume new forms under 
the influence of reagents. 

Bilin, the principal constituent of bile, may be isolated by the following pro- 
cesses, (a) The bile of the ox, after the separation of its mucus, is mixed with a 
little acetic acid, then filtered and precipitated by acetate of lead. The yellow 
precipitate, consisting of a combination of biliverdin, oleic and margaric acids 
with oxide of lead; is filtered, and the filtered liquid precipitated by a solution 
of the basic acetate of lead. The last precipitate, at first white; then yellow and 
plaster-like, contains fellinic acid in combination with a portion of the bile. 
Most of the bilin remains undissolved. The lead in the same solution is preci- 
pitated by sulphuretted hydrogen, and the solution remaining of bilin is evapo- 
rated carefully to dryness. The bilin so procured contains acetate of soda, and is 
likewise somewhat altered by the action of the free acetic acid during the evapo- 
ration. It is in this condition that bilin has been distinguished by the name of 
bile-sugar or picromef. 

(b) Ox-bile isevaporated to perfect dryness on a water-bath, reduced to powder 
and digested with anhydrous ether, which dissolves out all the fatty bodies not 
in combination with bases. The mass is then dissolved in alcohol, by which, 
mucus, common salt, &c. are left undissolved. To the filtered liquid a solution 
of chloride of barium is added, by small portions, at a time, so long as a dark 
green precipitate is formed. The last contains the biliverdin or colouring prin- 
ciple. The liquid filtered from it is then treated with barytes-water, added 
gradually so long as a precipitate falls. The colour of different portions of the 
precipitate, as they are successively produced, is dark gray, soon becoming 
green, then brownish yellow, and at last yellow. It contains, besides biliver- 
din, an orange-coloured matter, not yet investigated, and margaric acid. 

The liquid filtered from the last precipitate, after the precipitation of the free 
barytes it contains by carbonic acid, is evaporated to dryness, and the mass 
dissolved again in anhydrous alcohol, which leaves common salt and chloride 
of barium undissolved. Sulphuric acid mixed with an equal bulk of water, and 
then diluted by alcohol, is added gradually to the alcoholic solution to precipi- 
tate the bases it contains, in the form of sulphates. The liquid again filtered is 
mixed with freshly precipitated. carbonate of lead, for the purpose of combining 



TAURIN, CHOLIC ACID, FELLINIC ACID. 705 

its sulphuric acid and oily acids, and the greater proportion of the alcohol then 
distilled off. The liquid thus concentrated is filtered from the precipitate of 
lead salts, freed from lead in solution by sulphuretted hydrogen, filtered and 
evaporated to dryness in a water-bath. The transparent, yellow, bitter mass 
which remains, and which was formerly distinguished by Berzelius as biliary 
matter, is composed of bilin and fellinic acid. 

The last product is dissolved in water and digested with finely pulverized 
oxide of lead, by which it forms a plaster-like mixture of fellinate and cholinate 
of lead, and the bilin remains undissolved. The filtered solution of bilin is eva- 
porated to dryness; and to separate foreign matters, the mass is again dissolved 
in alcohol, filtered and evaporated to dryness. What remains is bilin. (Grun- 
driss der Organischen chemie von Dr. F. Wohler.) 

Bilin is a translucent, colourless, inodorous mass, without crystallization, 
having a bitter and at the same time somewhat sweetish taste. It contains ni- 
trogen, and is decomposed by heat, with the formation of ammoniacal products. 
Water and alcohol dissolve it in all proportions; it is insoluble in ether. Its so- 
lution in water is not precipitated by acids chlorine or metallic salts. Bilin is 
a readily alterable substance ; by boiling with caustic alkali, it is decomposed 
and resolved into cholic acid and ammonia. It is decomposed by acids into 
five different substances, namely ammonia, taurin, fellinic and cholinic acids, 
and dyslysin; a decomposition which may occur in the bile of the living 
body. 

When bilin is dissolved and digested in dilute hydrochloric acid, an oily sub- 
stance presents itself, consisting of bilin in combination with fellinic and cholinic 
acids, which by farther digestion changes into a resin-like mass, insoluble in 
water. The solution then contains sal-ammoniac and taurin; while the resin- 
ous mass consists of fellinic and cholinic acids with dyslysin. The two former 
may be dissolved out of the resinous mass by cold alcohol. 

Dyslysin remains undissolved in the last operation, as a resin-like mass. It 
dissolves, although with some difficulty, in boiling alcohol, and falls again, after 
evaporation and cooling, as a white earthy mass. It has not been farther in- 
vestigated. 

Taurin, C 4 H 7 N0 10 , discovered by Demarcay, is a neutral substance 
which crystallizes in colourless regular six-sided prisms terminated by four 
or six-sided pyramids, of a weak taste; and is fusible by heat without decom- 
position. It is soluble in fifteen and a half times its weight of water at 53°.6 
(12° centig.;) insoluble in absolute alcohol. It is dissolved without decom- 
position by concentrated sulphuric and nitric acids, and gives no reactions 
with the ordinary reagents. 

Taurin may be derived directly from unprepared bile, when the latter, after 
precipitation of its mucus by hydrochloric acid, is boiled for a long time with 
an excess of the same acid; the liquid is poured off from the precipitated resin- 
ous acids, concentrated by evaporation, mixed with alcohol and set aside. 
The Taurin crystallizes out mixed with common salt; the former is purified 
by solution in boiling water and crystallization. Taurin is the only one of 
these products that has been analyzed. 

Cholic aid may be prepared directly from bile, by precipitating the latter 
with acetate of lead, boiling the filtered solution with caustic potash, so long 
as ammonia escapes, and then adding acetic acid. The cholic acid separates 
in large white flocks, which soon assume a crystalline appearance. 

Cholic acid crystallizes in fine needles, which when pressed together form 
a mass of a silky lustre, of which the taste is at once sharp and sweet; it is 
fused by heat, and burns like a fat. It is sparingly soluble in water, highly- 
soluble in alcohol. It forms salts, with alkalies, of a sweet taste. 



706 FLUIDS SUBSERVIENT TO DIGESTION. 

Fellinic acid is contained, with bilin, and cholinic acid, in the plaster-like 
lead compound formed in the preparation of bilin, and in the alcoholic solu- 
tion of the resinous mass produced by the treatment of bilin by hydrochloric 
acid. Its separation from cholinic acid is effected by saturating the last men- 
tioned alcoholic solution with dilute ammonia and concentrating by evapora- 
tion: the cholinate of ammonia is then deposited as a hard mass, while the 
fellinate of ammonia remains dissolved. The addition of hydrochloric acid 
throws down the fellinic acid in white flocks. 

After being washed and dried, fellinic acid forms a white, earthy, inodorous 
and bitter mass which fuses without decomposition at 212°. In boiling wa- 
ter it undergoes fusion and dissolves to a small extent; in alcohol it dissolves 
easily and the solution has the bitter taste of bile; in ether it is also soluble. 
Its salts of alkaline bases are soluble both in water and alcohol, but inso- 
luble in an excess of alkali, and then precipitated as a plastic plaster-like sub- 
stance. The salts of lead and barytes, which are insoluble, have the same 
appearance. It enters into combination with bilin, and forms in union with it 
a compound acid, which should be named bilifellinic acid. 

Cholinic acid is separated from its salt of ammonia lately mentioned, by 
hydrochloric acid, in the form of white flocks, and becomes by aggregation, 
on drying, an easily pulverized mass. It is readily fused by the heat of hot 
water, in which it is wholly insoluble; it dissolves easily in alcohol. 

Biliverdin is separated from its compound with barytes, mentioned under 
bilin, by digestion in dilute hydrochloric acid which dissolves the barytes. 
The residue of biliverdin is purified by solution in alcohol and precipitation 
from the latter by water. It forms a brilliant, greenish brown tasteless mass, 
insoluble in water, dissolving easily in an alkali, and precipitated from that 
solution in green flocks by an acid. It dissolves of a fine green colour in hy- 
drochloric acid, and of a red tint in acetic acid. This principle of bile con- 
tains no nitrogen. The biliverdin of the bile of the ox appears to be 
identical with the chlorophyl of plants. That of carnivorous animals is 
different, although it may contain the same matter in combination with an- 
other substance. Such a substance appears to be the principal constituent 
of the yellow matter forming the concretions, found in the ox, which from the 
beauty and permanence of its tint is much prized by painters. These gall 
stones dissolve in caustic potash of a greenish-brown colour, giving a solution 
which when over-saturated with nitric acid, becomes first green, and rapidly 
in succession blue, violet and red, finally yellow. 

Cholesterin, C 37 H 32 0. — This is a crystallizable substance which may be 
dissolved out of inspissated bile, by ether; it is also a constituent of the brain 
and nerves. It is contained in largest proportion by the gall stones of the 
human subject, which generally consist of this substance combined with a 
portion of the yellow colouring matter of the bile. Cholesterin may be ob- 
tained by digesting these concretions in a solution of potash, by which the 
colouring matter is readily dissolved, and the cholesterin left white; or by 
dissolving them in boiling alcohol, in which the colouring matter is insoluble. 

Cholesterin crystallizes from an alcoholic solution in colourless small plates, 
of a pearly lustre ; is insoluble in water, tasteless, fuses at 278-°.0 (137° centig.,) 
and solidifies again in a crystalline condition. If strongly heated apart from air, 
it sublimes unchanged in a great measure, and condenses in plates. It is but 
sparingly soluble in cold alcohol ; is not altered by caustic alkalies. 

The bile appears to act as a stimulus to the intestinal canal' generally and to 
assist in dividing the chyme into chyle and fecal matter, by combining with the 
latter. 

Chyle. — This is the fluid, absorbed by the lacteal vessels from the small 



LIQUIDS OF SEROUS AND MUCOUS SURFACES. 707 

intestines during the process of digestion. As drawn from the thoracic duct of 
a mammiferous animal, it is an opaque milky liquid, in which two kinds of glo- 
bules are perceived by the microscope. This liquid has already a considerable 
resemblance to blood ; it soon coagulates ; the clot reddens in the air and con- 
tains fibrin. The serum which separates is composed, with the usual undeter- 
mined animal substances and salts, principally of albumen and fat, which last 
comes to the surface, and is what constitutes, without doubt, one of the two 
species of chyle-globules. 

Excrements. — The excrements of man usually contain about 25 per cent, of 
solid matter, which necessarily varies considerably with the nature of his food. 
Besides the indigestible residue of the food, it contains mucus, an undetermined 
extractive matter, fat, salts and the whole constituents of the bile, to which it 
owes its colour. From the incineration of 100 parts of dried excrements, 15 
parts of ashes have been obtained, which were principally composed of the phos- 
phates of lime and magnesia. The value of night soil as manure is ascribed 
•chiefly to these salts, and salts of ammonia from the urine. 



SECTION V. 



LIQUIDS OF SEROUS AND MUCOUS SURFACES AND PURULENT MATTER. 

Lymph. — The liquid which moistens the surface of cellular membrane is 
called lymph ; it is chiefly water, but contains a sensible quantity of common 
salt and of albumen, and when concentrated a trace of alkali sufficient to affect 
test-paper. 

The liquid secreted by serous membranes, such as the pericardium, pleura 
and peritoneum, resembles lymph, but contains so much as 7 or 8 per cent, of 
albumen and salts, and is distinctly alkaline, from the presence of carbonate or 
albuminate of soda. The liquor amnios and fluid of hydatides are of the same 
composition. The water of dropsy contains in addition urea, and cholesterin 
suspended in fine plates. All these liquids become turbid or coagulate, when 
boiled, or upon the addition of nitric acid to them. 

Mucus. — This is the liquid secreted by mucous surfaces, such as the nostrils. 
The mucus of the nostrils usually contains about 93 per cent, of water, 5 per 
cent, of mucus, with a trace of albumen and the usual salts. Mucus is insoluble 
in water, but imbibes it and swells up, so as to form a ropy liquid, as if it were 
dissolved. It shrinks up in concentrated acetic acid, and is not dissolved. 
When dry it is yellow. It dissolves in caustic alkali, and forms a thin liquid. 
Mucus contains nitrogen, but its composition is otherwise quite unknown. 

Pus. — The matter secreted by an inflamed and ulcerated surface is named 
pus. From a healing sore it is a yellowish white liquid, of the consistence of 
cream, which consists of round opaque globules floating in a transparent liquid. 
It is insoluble in water, but may be diffused through it; on standing, the glo- 
bules fall as a yellow sediment, and the supernatant liquid becomes clear and 
colourless. 

Pus contains about 86 per cent, of water, and 14 per cent, of solid matter. 
It is coagulated by heat and by alcohol. There have been found, by analysis, 
in pus, two albuminous principles, several fatty bodies besides cholesterin, with 
the usual salts and undetermined extractive matters. 

The matter of the corpuscles of pus considerably resembles the globulin of 



708 



BLOOD, MILK, URINE. 



blood. They are soluble in acetic acid with the exception of an exceedingly 
minute nucleus. The serum of pus contains albumen and another substance in 
larger quantity, to which the name pyin is applied, of which the solution in 
water is precipitated by alcohol, tannin, acetic acid, and most completely by 
alum, but not by ferrocyanide of potassium ; the precipitates are insoluble in an 
excess of the re-agents. 

From mucus pus is distinguished by its different external characters, by the 
different form and smaller size of its microscopic corpuscles,, by its different 
relations to water, and particularly by its becoming with caustic alkali, thick 
slimy and gelatinous, and in acetic acid assuming the appearance of an emul- 
sion, while mucus becomes thinner with an alkali, and with acetic acid coagu- 
lates as a flocky matter which unites into a thready mass k 



SECTION VI. 



BLOOD, MILK, URINE. 

Blood. — The constitution of the blood, has already been described under 
the principal constituents of the clot, fibrin, hematosin and globulin, and albu- 
men the chief constituent of the liquid portion. It is always alkaline from a 
salt of soda, probably the carbonate. 

The following table exhibits the results of two careful analyses of human 
blood by M. Lecanu. (Ann. de Chim. &c. xlviii. 308.) 



Water 

Fibrin 

Colouring matter (hematosin and globulin.) 

Albumen 

Crystalline fatty matter. 

Oily matter 

Extractive matter soluble in water and alcohol. 
Albumen combined with soda. 

Chloride of sodium 

— potassium, .... 

Carbonates 1 

Phosphates Vof potash and soda. 

Sulphates J 

Carbonates of lime and magnesia. 

Phosphates of lime, magnesia, and iron. 

Peroxide of iron. .... 

Loss 



1 

i 

J 

} 



Human blood. 


780.145 


785.590 


2.100 


3.565 


133.000 


119.626 


65.090 


69.415 


2.430 


4.300 


1.310 


2.270 


1.790 


1.920 


1.265 


2.010 



8.370 7.304 



2.100 
2.400 



1.414 
2.586 



100.000 100.000 



Milk. — The history of this fluid has been partly given under its characte- 
ristic constituents casein, milk-sugar, and the acids of butter. It contains from 
10 to 13 per cent, of solid matter, the rest is water. It is not coagulated by 
heat, but readily by all sour liquids and by rennet. When heated, a skin of 



URINE. 709 

coagulated casein forms on its surface. The butter of milk consists of marga- 
rine, oleine and butyrine (page 646.) 

Milk may be made to undergo the vinous fermentation, although very 
slowly, and only after it contains lactic acid; which acid probably converts the 
milk-sugar into grape-sugar before the fermentation occurs. 

An excellent examination has been made by MM. O. Henry and A. Cheval- 
lier, of the comparative composition of woman's milk, the milk of the cow 
and ass, of which I subjoin the results. (Journal de Pharmacie XXV. 333 
et 401. 

ORDINARY MILK. 





Woman. 


Ass. 


Cow. 


Cheese. 


. 1.52 


1.82 


4.48 


Butter.^ 


. 3.55 


0.11 


3.13 


Sugar of milk. 


. 6.50 


6.08 


4.77 


Salts (or mucous matter.) 


. 0.45 


0.34 


0.60 


Water. 


. 87.98 


91.65 


87.02 



100.00 100.00 100.00 

Urine. — This fluid is secreted by the kidneys from the arterial blood. The 
average density of healthy human urine is 1.0125, but it occasionally rises to 
1.030; it is acid from free lactic acid. On standing it deposites a slimy mucus, 
and after a time, when stale, becomes alkaline from the formation of carbonate 
of ammonia. The latter salt is produced from the urea, which is accompanied 
in urine by a minute quantity of a fermenting principle, which occasions this 
transformation. Urine in its usual condition contains from 7 to 8 per cent, of 
solid matter, the rest is water. Its characteristic constituents are urea (page 
671) and uric acid (page 677;) the former is free or in combination with lactic 
acid, the last is an unknown combination. 

Besides its usual saline constituents, the urine may contain in solution 
various bodies drawn by the kidneys from the blood. Many salts, such as 
nitrate of potash, ferrocyanide of potassium, pass through the circulation and 
are thrown off by the urine unaltered; so also are the organic acids, tartaric, 
oxalic, &c. when free; but the salts with alkalies of the same acids appear in 
the state of carbonates, and render the urine alkaline. 

M. Lecanu has obtained some valuable results respecting the proportions of 
these substances in the urine of man, as affected by age and sex, which he de- 
duces from a series of 120 analyses of urine. 

He found that the quantity of urea passed in twenty-four hours, is in gram- 
mes (1 gramme = 15.44 grains troy:) 





Minimum 


Mean 


Maximum 


By men. .... 


. 23.155 


28.0525 


33.055 


By women 


. 9.926 


19.1165 


28.307 


By old men (84 to 86 years.) .. 


. 3.956 


8.1105 


19.116 


By children of eight years. 


. 10.478 


13.4710 


16.464 


By children of four years. 


. 3.710 


4.5050 


5.300 



The quantity of uric acid discharged is, like the urea, sensibly the same for 
the same individual in equal times, but varies mUch in different individuals. 
This difference was found to be in the twenty-fours, 0.362 to 1.343 grammes 
60 



710 URINARY CONCRETIONS. 

in the male adults, 0.229 to 0.652 in the old men, 0.394 toO.907 in the women, 
and 0.198 to 0.32 in the children. (Journ. de Pharmacie, XXV, 681 et 746.) 
The following analysis by Berzelius exhibits the composition of urine in its 
ordinary state, in 1000 parts: 

Water. 933.00 

Urea 30.10 

Uric acid. . . . . . . . . . 1.00 

Free lactic acid, lactate of ammonia, and animal matter 

not separable from them. ..... 17.14 

Mucus of the bladder 0.32 

Sulphate of potash 3.71 

Sulphate of soda 3.16 

Phosphate of soda 2.94 

Phosphate of ammonia. ...... 1.65 

Chloride of sodium 4.45 

Hydrochlorate of ammonia. ; 1.50 

Earthy matters, with a trace of fluate of lime. . . 1.00 

Siliceous earth 0.03 



URINARY CONCRETIONS. 

There are several distinct species of urinary calculi. 

1. Xanthic oxide, a very rare calculus, discovered by Dr. Marcet. It has a 
light brown or bright brown surface; its fracture is scaly, with a brown or deep 
flesh colour, and becoming resinous by friction. It is distinguished by being 
entirely soluble in caustic potash, and precipitated by carbonic acid. It is 
thrown down as a white precipitate, which agglutinates in drying, and forms a 
pale-yellow, hard mass, which acquires a waxy lustre by friction. It is soluble 
in alkaline carbonates; also in nitric acid without effervescence. Its compo- 
sition is expressed by C 5 N 2 H 2 2 . 

2. Cystic oxide, a rare calculus, discovered by Dr. Wollaston. It appears, 
when broken, to form a yellowish-white, confused crystalline mass, having a 
brilliant waxy lustre. It is distinguished by its solubility in caustic potash, 
from which it is deposited on the addition of acetic acid, in hexagonal plates. 
It is also soluble in ammonia. The mineral acids dissolve cystic oxide with 
ease, and form crystalline compounds with it. The compound with hydro- 
chloric acid is anhydrous, and contains 1 atom of cystic oxide and of the acid. 
The nitrate contains 2 atoms of water, one of which it loses at 105.° The 
solution of cystic oxide in an alkali or alkaline carbonate is decomposed by 
heat, ammonia first coming off, and then as the evaporation proceeds, a com- 
bustible gas which smells like sulphuret of carbon. This calculus contains 
sulphur, and is represented by C 6 NH 6 4 S 2 (Thaulow.) 

3. Oxalate of lime, or mulberry calculus, has a dark coloured tuberculated 
surface, is very hard and compact, rarely large. It is easily distinguished by 
the circumstance that its powder does not dissolve in acetic acid; but after 
being heated on a spatula to low redness, in the flame of a spirit lamp, it dis- 
solves readily in that acid with effervescence, the oxalate of lime having been 
converted into carbonate. The composition of crystallized oxalate of lime is 
CaO,C 2 3 +2HO. 

4. Bone-earth calculus; its surface is pale-brown and quite smooth, as if it 
had been polished. \t is compact, and when sawed through, appears very 
regularly laminated. It is distinguished by its powder dissolving in dilute 
nitric and hydrochloric acid, but not in acetic acid, nor in solution of caustic 



SOLID PARTS OF ANIMALS. 7 1 1 

potash. It appears white and not easily fused before the blow-pipe. The 
composition of bone-earth is expressed by 8CaO,HO-f3P0 5 . 

2. JLmmoniaco-magnesian phosphate calculus is composed of the phos- 
phate of magnesia and ammonia, which precipitates in granular crystals when 
phosphoric acid is added to a mixed solution of a salt of magnesia and ammo- 
nia (page 357.) It is white and less compact than the last, and sparkling 
crystals of the salt are often perceptible in the mass. It emits ammonia when 
heated to 212°, is dissolved by cold acetic acid and precipitated again on neu- 
tralizing the acid. It emits ammonia when digested in a solution of potash, 
but does not dissolve. It fuses into a white pearly globule by strong heat of 
the blow-pipe. The composition of crystallized phosphate of magnesia and 
ammonia is 2MgO,NH 4 0,P0 5 -fl4HO. 

6. The fusible calculus is a mixture of the last two, common in old and 
exhausted subjects, and often attains a large size. It is commonly white, 
rather friable and chalky; its fracture rugged and uneven, and surface dusty. It 
melts easily before the blow-pipe into a pearly globule. Part of it dissolves 
in acetic acid, the rest in hydrochloric acid. 

7. The uric acid calculus is perhaps the most common. It is usually of 
an oval form, of a brownish or fawn colour and smooth surface, and composed 
of concentric layers round a central nucleus, which is often foreign matter. 
Consisting of volatile elements, like the first and second species, it is con- 
sumed before the blow-pipe, leaving only a trace of white ash. The powder 
of this calculus is soluble in a dilute and warm solution of caustic potash, and 
on adding an acid, uric acid is precipitated as a white powder. It is dissolved 
with effervescence by nitric acid of the ordinary strength, and the solution 
when evaporated nearly to dryness, and treated with a drop of ammonia ex- 
hibits the beautiful pink colour of murexide (see uric acid, page 677.) The 
formula for uric acid is C 10 H 4 N v O 6 . 

8. The urate of ammonia forms a comparatively rare calculus. It has the 
chemical properties of the last species, with the additional property of emitting 
ammonia when dissolved in a dilute and warm solution of caustic potash. 



SECTION VIII. 



SOLID PARTS OF ANIMALS. 

Bones. — When bones are digested in very dilute hydrochloric acid, their 
earth is dissolved out, and an organic matter remains, consisting of cartilage, 
which retains the form of the bones. This matter when moist is flexible and 
elastic; by drying it shrivels up and becomes brittle, but remains translucent. 
It is entirely dissolved by boiling in water, and gives a solution of gelatin 
(page 698.) Water heated above 212°, under pressure, dissolves the carti- 
laginous matter entirely out of bones, and leaves the pure bone-earth. 

When bones are distilled in a close vessel, they yield ammonia and oily 
volatile products, while the earth remains behind, black, from the presence of 
8 or 10 per cent, of charcoal, which in this divided state and associated with 
the earth, has a high decolourizing power. It forms animal charcoal, bone or 
ivory black. Bones burn white, on the other hand, in an open fire, and leave 
the bone-earth. The phosphate of lime in bones is peculiar, it contains 8 
proportions of lime to 3 of phosphoric acid, or 8CaO+3P0 5 ; but it is un- 



712 TEETH, SKIN, ECT. 

doubtedly a compound of two tribasic phosphates of lime, namely, 2CaO,HO, 
P0 5 -f 2(3CaO,PO s ;) containing 1 atom of water before calcination. The 
proportion between the earth and cartilage varies in different bones; the hu- 
man scapula has been found to contain 54£, the temporal bone 63| per cent, 
of bone-earth. Human bones well dried are said to contain 11 percent, of 
carbonate of lime, which is three times the quantity in the bones of the ox. 
Fluoride of calcium is also found in bones, although not uniformly present ac- 
cording to Dr. Rees' observations. The salt in question occurs in fossil bones, 
and is contained in considerable quantity in the human bones found in Hercu- 
laneum. In weak or ricketty bones the proportion of bone-earth has been 
found diminished by 14 per cent. M. Valentin finds, by the analysis of mor- 
bid osseous formations, that the callus and exostosis contain more carbonate of 
lime than the sound bone upon which they form, and that, on the contrary, 
the caries contains a quantity of carbonate of lime smaller by several per cent, 
than the sound bone. 

The teeth are composed of the same materials as bone, but contain less car- 
tilage; usually about 64 per cent, of phosphate of lime, about 6 per cent, of 
carbonate of lime with carbonate of magnesia, and 28 per cent, of cartilage. 
The ivory of the teeth contains no cartilage, about 88 per cent, of phosphate 
of lime, with some fluoride of calcium, and 10 per cent, of carbonate of lime, 
with magnesia. The antlers of deer have the same composition as bone. 

Skin. — The cuticle or epidermis is a coating of horny matter (page 701,) 
without blood-vessels. The mucous membrane (rete Malpighi,) between 
the cuticle and true skin, appears to consist of the matter of the epidermis not 
yet hardened. The corium or true skin is completely decomposed by diges- 
tion in boiling water, and yields a solution of gelatin (page 698.) The com- 
position and peculiar characters of the organic matter in nails, claivs, hoofs, 
hair, wool, and feathers, have already been described (pages 701, 702.) All 
these substances contain, besides, from h to % per cenU of bone-earth. 

Human perspiration has an acid reaction, it is supposed from acetic acid, 
but from its observed effects upon the dyed colours of prints, it must occa- 
sionally be formic acid. Its fixed constituents amount to from £ to 1| per 
cent., and consist of an undetermined animal matter, sal-ammoniac, lactate of 
ammonia, chloride of sodium, and the other usual salts. 

Muscle. — The threads or fibres of muscle consist essentially of fibrin (page 
691,) but in addition to fibrin, several other substances are present, of which 
the nature is very imperfectly known. Flesh strongly dried, leaves about 23 
per cent, of solid matter, the other 77 per cent, are water. Of the dry mass, 
about 6 per cent, dissolves in water. Water extracts from hashed meat, about 
17 per cent, of its weight. This extract of meat is partly soluble in alcohol 
and partly insoluble. It is a mixture of salts with several organic substances, 
of which the true nature is still very doubtful. These undetermined extrac- 
tive matters occur also in urine and most of the animal fluids. To one of 
them, soluble in both water and alcohol, and the cause of the odour of cooked 
meat, the name osmazome has been applied, but the matter so named has not 
the characters of a pure substance. 

The fibrin of all animals is similar, for it has been found by Leibig, that the 
flesh of the ox, the deer, the cod and pike do not differ in composition. 

The composition of ligaments, cartilage, tendons, &c. has already been 
described (p. 698.) 

Fat. — Human fat appears to contain no stearine, but only margarine (page 
649,) and oleine (page 653.) Tallow, or the melted fat of oxen and sheep, 
on the other hand, consists chiefly of stearine (page 651,) with a little oleine. 
It fovrns excellent hard soapSy in the preparation of which, the melted tallow 



BRAIN AND NERVES. 713 

is boiled with a solution of caustic soda, weak at first, but gradually increased 
in strength; the soap floats upon the alkaline liquor, in which it is insoluble, 
while the glycerine of the tallow, which has been replaced in combination 
with the stearic and oleic acids, by soda, is dissolved by the water. In the 
formation of the common diachylon planter, 9 parts of olive oil and some 
water are boiled with 5 parts of levigated litharge; a compound of margaric 
and oleic acids with the oxide of lead results, which forms a plastic mass, and 
is an insoluble soap. Hog's lard contains more oleine than tallow, and is 
softer; it probably, like human fat, contains margarine, although stearine also 
is undoubtedly present. 

Brain and nerves. — The substance of the brain has been examined by more 
than one chemist, but most recently by M. Fremy. The brain of man con- 
tains 7 parts of albumen, 5 parts of a fatty matter, and 80 parts of water. 
The albuminous portion, after being coagulated by heat, is insoluble in water, 
alcohol and ether. The fatty matter is what has principally occupied atten- 
tion; besides portions of the ordinary fatty substances, it contains two pecu- 
liar acids and chloresterin: 

1. Cerebric acid which when purified is white, and presents itself in crys- 
talline grains. It dissolves without residue in boiling alcohol, is almost inso- 
luble in cold ether, more soluble in boiling ether. It has the remarkable pro- 
perty of swelling up like starch in boiling water, but appears to be insoluble 
in that liquid. It enters into fusion at a high temperature, approaching closely 
that at which it is decomposed, and is combustible. It contains no sulphur, 
but some phosphorus. The result of its analysis by Fremy, is 66.7 per cent, 
of carbon, 10.6 of hydrogen, 2.3 of nitrogen, 0.9 of phosphorus, 19.5 of 
oxygen. 

2. Oleophosphoric acid, which is separated from the former acid, by its 
solubility in ether. It is still accompanied by oleine and cholesterin, which 
are withdrawn from it by alcohol and ether. This acid is of a viscid consist- 
ence, insoluble in cold alcohol, but dissolving easily in boiling alcohol; it is 
insoluble in ether. Placed in contact with potash, soda and ammonia, it im- 
mediately gives soapy compounds. It forms compounds insoluble in water 
with other bases. M. Fremy has observed a remarkable transformation of 
oleophosphoric acid. When boiled for a long time in water or alcohol, it 
gradually loses its viscidity and becomes a fluid oil, which is pure oleine; 
while the liquor contains phosphoric acid. This decomposition becomes very 
rapid, when the liquor is rendered slightly acid. Although M. Fremy's at- 
tempts to form this acid directly, by uniting oleine and phosphoric acid, were 
unsuccessful, he still deems it probable that this acid may consist of the ele- 
ments in question, and be analogous to the compound of sulphuric acid and 
oleine or sulpholeic acid (page 655.) It contains from 1.9 to 2 per cent, of 
phosphorus, in the condition, it is thus represented, of phosphoric acid. 

M. Fremy has given a process for extracting cholesterin (page 706) from 
the brain, in considerable quantity. 

The constituents of the brain of man, enumerated by Fremy, are: 1. Cere- 
bric acid free or combined with soda, or with phosphate of lime. 2. Oleo- 
phosphoric acid free and combined with soda. 3. Oleine and margarine. 
4. Minute quantities of oleic and margaric acids. 5. Cholesterin. 6. Water 
and an albuminous matter. These results are quite different from those pre- 
viously obtained by M. Couerbe, whose method of investigation appears to 
have been defective. 

Fremy found a considerable quantity of cerebral matter in the spinal mar- 
row, and very appreciable quantities of it in certain nerves. 

The, eye. — The sclerotica is dissolved, like the corium, by long boiling with 

60* 



714 SOLID PARTS OF ANIMALS. 

water, and gives a solution of gelatin; it is said to contain no fibrin. The 
cornea is composed of cartilaginous fibres, and therefore consists of chondrin; 
but it contains besides, a small quantity of fibrin or albumen. The pigmen- 
tum nigrum (page 703) has considerable resemblance to hematosin. The 
vitreous and aqueous humours consist of water with about I5 per cent, of 
common salt, a little albumen and undetermined animal matter. The sub- 
stance of the crystalline lens agrees in properties with the globulin of the 
blood, and may be represented as a compound of 15 atoms of protein with 1 
atom of sulphur. When rubbed in pure water, the greater part of the crys- 
talline dissolves; the solution is coagulated by heat, and forms a granular and 
not a coherent mass. The crystalline undergoes the same coagulation when 
put into hot water, into alcohol, or into an acid, ' 



( 715 ) 



APPENDIX. 



TABLE I. 

For the conversion of degrees on the Centigrade thermometer into degrees 

of Fahrenheit's scale. 



Cent. 


Fahr. 


Cent. 


Falir. 


Cent. 


Fahr. 


—50° 


— 58°.0 


— 9° 


15°. 8 


32° 


89°.6 


—49 


—56 .2 


— 8 


17 .6 


33 


91 .4 


—48 


—54 .4 


— 7 


19 .4 


34 


93 .2 


—47 


—52 .6 


— 6 


21 .2 


35 


95 .0 


—46 


—50 .8 


— 5 


23 .0 


36 


96 .8 


—45 


—49 .0 


— 4 


24 .8 


37 


98 .6 


—44 


—47 .2 


— 3 


26 .6 


38 


100 .4 


—43 


—45 .4 


— 2 


28 .4 


39 


102 .2 


—42 


—43 .6 


— 1 


30 .2 


40 


104 .0 


—41 


—41 .8 





32 .0 


41 


105 .8 


—40 


—40 .0 


+ 1 


33 .8 


42 


107 .6 


—39 


—38 .2 


2 


35 .6 


43 


109 .4 


—38 


—36 .4 


3 


37 .4 


44 


111 .2 


—37 


-i-34 .6 


4 


39 .2 


45 


113 .0 


—36 


—32 .8 


5 


41 .0 


46 


114 .8 


—35 


—30 .0 


6 


42 .8 


47 


116 .6 


—34 


—29 .2 


7 


44 .6 


48 


118 .4 


—33 


—27 .4 


8 


46 .4 


49 


120 .'2 


—32 


—25 .6 


9 


48 .2 


50 


122 .0 


—31 


—23 .8 


10 


50 .0 


51 


123 .8 


—30 


—22 .0 


11 


51 .8 


52 


125 .6 


—29* 


—20 .2 


12 


53 .6 


53 


127 .4 


—28 


—18 .4 


13 


55 .4 


54 


129 .2 


—27 


—16 .6 


14 


57 .2 


55 


131 .0 


—26 


—14 .8 


15 


59 .0 


56 


132 .8 


—25 


—13 .0 


16 


60 .8 


57 


134 .6 


—24 


— 11 .2 


17 


62 .6 


58 


136 .4 


—23 


— 9 .4 


18 


64 .4 


59 


138 .2 


—22 


— 7 .6 


19 


66 .2 


60 


140 .0 


—21 


— 5 .8 


20 


68 .0 


61 


141 .8 


—20 


— 4 .0 


21 


69 .8 


62 


143 .6 


—19 


— 2 .2 


22 


.71 .6 


63 


145 .4 


— 18 


— .4 


23 


73 .4 


64 


147 .2 


—17 


+ 1 .4 


24 


75 .2 


65 


149 .0 


—16 


3 .2 


25 


77 .0 


66 


150 .8 


—15 


5 .0 


26 


78 .8 


67 


152 .6 


—14 


6 .8 


27 


80 .6 


68 


154 .4 


—13 


8 .6 


28 


82 .4 


69 


156 .2 


—12 


10 .4 


29 


84 .2 


70 


158 .0 


—11 


12 .2 


30 


86 .0 


71 


159 .8 


—10 


14 .0 


31 


87 .8 


72 


161 .6 



71& 



APPENDIX. 



Cent. 



Fahr. 



Cent. 



Fahr. 



Cent. 



Fahr. 



73° 


163°.4 


121° 


249°.8 


169° 


336°.2 


74 


165 .2 


122 


251 .6 


170 


338 .0 


^5 


167 .0 


123 


253 .4 


171 


339 .8 


76 


168 £ 


124 


255 .2 


172 


341 .6 


77 


170 ..6 


125 


257 .0 


173 


343 .4 


78 


172 .4 


126 


258 .8 


174 


345 .2 


79 


174 .2 


127 


260 .6 


175 


347 .0 


80 


176 .0 


128 


262 .4 


176 


348 .8 


81 


177 .8 


129 


264 .2 


177 


350 .6 


82 


179 .6 


130 


266 .0 


178 


352 .4 


83 


181 .4 


131 


267 .8 


179 


354 .2 


84 


183 .2 


132 


269 .6 


180 


356 .0 


85 


185 .0 


133 


271 .4 


181 


357 .8 


86 


186 .8 


134 


273 .2 


182 


359 .6 


87 


188 .6 


135 


275 .0 


183 


361 .4 


88 


190 .4 


136 


276 .8 


184 


363 .2 


89 


192 .2 


137 


278 .6 


185 


365 .0 


90 


194 .0 


138 


280 .4 


186 


366 .8 


91 


195 .8 


139 


282 .2 


187 


368 .6 


92 


197 .6 


140 


284 .0 


188 


370 .4 


93 


199 .4 


141 


285 .8 


189 


372 .2 


94 


201 .2 


142 


287 .6 


190 


374 .0 


95 


203 .0 


143 


289 .4 


191 


375 .8 


96 


204 .8 


144 


291 .2 


192 


377 .6 


97 


206 .6 


145 


293 .0 


193 


379 .4 


98 


208 .4 


146 


294 .8 


194' 


381 .2 


99 


210 .2 


147 


296 .6 


195 


383 .0 


100 


212 .0 


148 


298 .4 


190 


384 .8 


101 


213 .8 


149 


300 .2 


197 


386 .6 


102 


215 .6 


150 


302 .0 


198 


388 .4 


103 


217 .4 


151 


303 .8 


199 


390 .2 


104 


219 .2 


152* 


305 .6 


200 


392 .0 


105 


221 .0 


153 


307 .4 


201 


3Q3 .8 


106 


222 .8 


154 


309 .2 


202 


395 .6 


107 


224 .6 


155 


311 .0 


203 


397 .4 


108 


226 .4 


156 


312 .8 


204 


399 .2 


109 


228 .2 


157 


314 .6 


205 


401 .0 


110 


230 .0 


158 


316 .4 


206 


402 .8 


111 


231 .8 


159 


318 .2 


207 


404 .6 


112 


233 .6 


160 


320 .0 


208 


406 .4 


113 


235 .4 


161 


321 .8 


209 


408 .2 


114 


237 .2 


162 


323 .6 


210 


410 .0 


115 


239 .0 


J 63 


325 .4 


211 


411 .8 


116 


240 .8 


164 


327 .2 


212 


413 .6 


117 


242 .6 


165 


329 .0 


213 


415 .4 


118 


244 .4 


166 


330 .8 


214 


417 .2 


119 


246 .2 


167 


332 ,6 


215 


419 .0 


120 


248 .0 


168. 


334 .4 1 


216 


420 .8 



APPENDIX. 



717 



Cent. 


Fahr. 


Cent. 


Fahr. 


Cent. 


Fahr. 


217° 


422° .6 


252° 


485°.6 


287° 


548°.6 


218 


424 .4 


253 


487 .4 


288 


550 .4 


219 


426 .2 


254 


489 .2 


289 


552 .2 


220 


428 .0 


255 


491 .0 


290 


554 .0 


221 


429 .8 


256 


492 .8 


291 


555 .8 


222 


431 .6 


257 


494 .6 


292 


557 .6 


223 


433 .4 


258 


496 .4 


293 


559 .4 


224 


435 ,2 


259 


498 .2 


294 


561 .2 


225 


437 .0 


260 


500 .0 


295 


563 .0 


226 


438 .8 


261 


501 .8 


296 


564 .8 


227 


440 .6 


262 


503 .6 


297 


566 .6 


228 


442 .4 


263 


505 .4 


298 


568 .4 


229 


444 .2 


264 


507 .2 


299 


570 .2 


230 


446 .0 


265 


509 .0 


300 


572 .0 


231 


447 .8 


266 


510 .8 


301 


573 .8 


232 


449 .6 


267 


512 .6 


302 


575 .6 


233 


451 .4 


268 


514 .4 


303 


577 .4 


234 


453 .2 


269 


516 .2 


304 


579 .2 


235 


455 .0 


270 


518 .0 


305 


581 .0 


236 


456 .8 


271 


519 .8 


306 


582 .8 


237 


458 .6 


272 


521 .6 


307 


584 .6 


238 


460 .4 


273 


523 .4 


308 


586 .4 


239 


462 .2 


274 


525 .2 


309 


588 .2 


240 


464 .0 


275 


527 .0 


310 


590 .0 


241 


465 .8 


276 


528 .8 


311 


591 .8 


242 


467 .6 


277 


530 .6 


312 


593 .6 


243 


469 ,4 


278 


532 .4 


313 


595 .4 


244 


471 .2 


279 


534 .2 


314 


597 .2 


245 


473 .0 


280 


536 .0 


315 


599 .0 


246 


474 .8 


281 


537 .8 


316 


600 .8 


247 


476 .6 


282 


539 .6 


317 


602 .6 


248 


478 .4 


283 


541 .4 


318 


604 .4 


249 


480 .2 


284 


543 .2 


319 


606 .2 


250 


482 .0 


285 


545 .0 


320 


608 .0 


251 


483 .8 


286 


546 .8 







718 



APPENDIX. 



TABLE II. 



TABLE of the elastic Force of Aqueous Vapour at different Temperatures, 
expressed in Inches of Mercury. 



Temp. 


Force of Vapour. 


Temp. 


Force of Vapour. 


Temp. 


Force of Vapour. 


Dalton. 


Ure. 


Dalton. 


Ure. 


Dalton. 


Ure. 


32° F. 


200 


0.200 


80° F. 


1.00 


1.010 


128°F. 


4.11 




33 


0.207 




81 


104 




129 


4.22 




34 


0.214 




82 


1.07 




130 


4.34 


4.366 


35 


0.221 




83 


1.10 




131 


4.47 




36 


0.229 




84 


1.14 




132 


4.60 




37 


0.237 




85 


1.17 


1.170 


133 


4.73 




38 


0.245 




86 


1.21 




134 


4.86 




39 


0.254 




87 


1.24 




135 


5.00 


5.070 


40 


0.263 


0.250 


88 


1.28 




136 


5.14 




41 


0.273 




89 


132 




137 


5.29 




42 


0.283 




90 


1.36 


1.360 


138 


5.44 




43 


0.294 




91 


1.40 




139 


5.59 




44 


0.305 




92 


1.44 




140 


5.74 


5.770 


45 


0.316 




93 


1.48 




141 


5.90 




46 


0.328 




94 


1.53 




142 


6.a5 




47 


0.339 




95 


1.58 


1.640 


143 


6.21 




48 


0.351 




96 


1.63 




144 


6.37 




49 


0-363 




97 


1.68 




145 


6.53 


6.600 


50 


0-375 


0.360 


98 


1.74 




146 


6.70 




51 


0-388 




99 


1.80 




147 


6.87 




52 


0401 




100 


1.86 


1.860 


148 


7.05 




53 


0-415 




101 


1.92 




149 


7.23 




54 


0-429 




102 


1.98 




150 


7.42 


7.530 ; 


55 


0443 


0.416 


103 


2.04 




151 


7.61 




56 


0-458 




104 


211 




152 


7.81 


i 


57 


0-474 




105 


2.18 


2.100 


153 


8.01 




58 


0490 




106 


2.25 




154 


8.20 


!' 


59 


0-507 




107 


2.32 




155 


8.40 


8.500 


60 


0524 


0.516 


108 


2.39 




156 


8.60 




61 


0-542 




109 


246 


157 


8.81 




62 


560 




110 


253 12.456 


158 


9.02 




63 


0-578 




111 


2.60 




159 


9.24 




64 


0-597 




112 


2.68 




160 


9.46 


9.600 


65 


0-616 


0.630 


113 


2.76 




161 


9.68 




66 


0-635 




114 


2.84 


162 


9.91 




67 


0-655 




115 


2.92 |2.820 


163 


10.15 




68 


676 




116 


3.00 


164 


10.41 




69 


0-698 




117 


3.08 




165 


10.68 


10.800 


70 


0-721 


0.726 


118 


3.16 




166 


10.96 




71 


0745 




119 


3.25 




167 


11.25 




72 


0-770 




120 


3.33 


2.300 


168 


11.54 




73 


0-796 




121 


3.42 




169 


11.83 




74 


0-823 




122 


3.50 




170 


12.13 


12.050 


75 


0851 


0,860 


123 


3.59 




171 


12.43 




76 


0-880 




124 


3.69 




172 


12.73 




77 


0910 




125 


3.79 


3.830 


173 


1302 




78 


0-940 




126 


3.89 




174 


13.32 




79 


0971 




127 


4.00 




175 


15.62 


L3.550 1 



APPENDIX. 



719 



Temp. 


Force of Vapour. 


Temp. 


Force of Vapour. 


Temp. 


Force of Vapour. 


i 










Dalton. | Ure. 




Dalton. 


Ure. 




Dalton. 


Ure. 


176°F. 


13.92 




20PF 


24.12 




226°R 


38.89 


40.100 


177 


14.22 




202 


24.61 




227 


39.59 




178 


14.52 




203 


25.10 




228 


40.30 




179 


14.83 




204 


25.61 




229 


41.02 




180 


15.15 


15.160 


205 


26.13 


25.900 


230 


41.75 


43.100 


181 


15.50 




206 


26.66 




231 


42.49 




1S2 


15.86 




207 


27.20 




232 


4324 




183 


16.23 




208 


27.74 




233 


44.00 




184 


16.61 




209 


28.29 




234 


44.78 


46.800 


185 


17.00 


16.900 


210 


28.84 


28.880J235 


45.58 


47.220 


186 


17.40 




211 


29.41 


236 


46.39 




187 


17.80 




212 


30.00 


30.000 237 


47.20 




188 


18.20 




213 


30.60 


238 


48.02 


50.300 


189 


18.60 




214 


31.21 




239 


48.84 




190 


19 00 


19.000 


215 


31.83 




240 


49.67 


51.700 


191 


| 19.42 




216 


32.46 


33.400 


241 


50.50 




192 


i 19.86 




217 


3309 




242 


51.34 


53.600 


193 


i 20.32 




218 


33.72 




243 


52.18 




194 


j 20.77 




219 


34.35 




244 


5303 




195 


| 21.22 


21.100 


220 


34.99 


35.540 


245 


5383 


56.340 


196 


! 21.68 




221 


3563 


36.700 


246 


54.63 




197 


j 22 13 




222 


36.25 




247 


55.51 




198 


22 69 




223 


i 36.88 




248 


56.42 


60.400 


199 


23.16 




224 


| 37.53 




249 


57.31 




200 


23 64 


2360C 


225 


| 38.20 


39.110 


250 


58.21 


61.900 



720 



APPENDIX. 



TABLE III. 



Dr. lire's Table of the quantity of Oil of Vitriol, of sp. gr. 1.8485, and of 
tftnhy droits dcid, in 100 Parts of dilute Sulphuric Acid, at different Den- 
sities. 



Liquid. 


Sp. Gr. 


Dry. 


| Liquid. 

i 


Sp. Gr. Dry. 


Liquid 


Sp. Gr. 


Dry. 


100 


1.8485 


81.54 


66 


1.5503 53.82 


32 


1.2334 


26.09 


99 


1.8475 


80.72 


65 


1.5390 53.00 


31 


1.2260 


25.28 


98 


1.8460 


79.90 


64 


1.5280 52.18 


30 


1.2184 


24.46 


97 


1.8439 


79,09 


63 


! 1.5170 51.37 


29 


1.2108 


23.65 


96 


1.8410 


78.28 


62 


1.5066 50.55 


28 


1.2032 


22.83 


95 


1.8376 


77.46 


61 


1.4960 49.74 


27 


1.1956 


22.01 


94 


1.8336 


76.65 


60 


1.4860 48.92 


26 


1.1876 


21.20 


93 


1.8290 


75.83 


59 


1.4760 48.11 


25 


1.1792 


1 20.38 


92 


1.8233 


75.02 


58 


1.4660 47.29 


24 


1.1706 


1957 


91 


1.8179 


74.20 


57 


1.4560 46.48 


23 


1.1626 


18.75 


90 


1.8115 


73.39 


56 


1.4460 45.66 


22 


1.1549 


17.94 


89 


1.8043 


72 57 


55 


1.4360 44.85 


21 


1.1480 


17.12 


88 


1.7962 


71.75 


54 


1.4265 44.03 


20 


1.1410 


16.31 i 


87 


1.7870 


70.94 


53 


1.4170 43 22 


19 


1.1330 


1549 


86 


1.7774 


70.12 


52 


1.4073 42.40 


18 


1.1246 


14.68 


85 


1.7673 


69.31 


51 


1.3977 41.58 


17 


1.1165 


13.86 


84 


1.7570 


68.49 


50 


1.3884 40.77 


16 


1.1090 


13.05 


83 


1.7465 


67.68 


49 


1.3788 39.95 


15 


1.1019 


12.23 


82 


1.7360 


66 86 


48 


1.3697 39.14 


14 


1.0953 


11.41 


81 


1.7245 


66.05 


47 


1.3612 38.32 


13 


1.0887 


10.60 ! 


80 


1.7120 65-23 


46 


1.3530 37.51 


12 


1.0809 


9.78 


79 


1.6993: 64.42 


45 


1.3440 36.69 


11 


1.0743 


8.97 I 


78 


1.6870' 63.60 


44 


1.3345 35.88 


10 


1.0682 


8.15 


77 


1.6750 62.78 


43 


1.3255 35.06 


9 


1.0614 


7.34 


76 


1.6630 


61.97 


42 


1.3165 34.25 


8 


1.0544 


6.52 


75 


1.6520 


61.15 


41 


1.3080 33.43 


7 


1.0477 


5.71 


74 


1.6415 


60 34 


40 


1.2999 32.61 


6 


10405 


4.89 


73 


1.6321 


59.52 


39 


1.2913 31.80 


5 


1.0336 


4.08 


72 


1.6204 


58.71 


38 


1.2826 30.98 


4 


1.0268 


3.26 


71 


1.6090 


57.89 


37 


1.2740 30.17 


3 


1.0206 


2.446 


70 


1.5975 


57.08 


36 


1.2654 


29.35 


2 


1.0140 


1.63 


69 


1.5868 


56.26 


35 


1.2572 


28.54 


1 


1.0074 


0.8154 


68 


1.5760 


55.45 


34 


1.2490 


27.72 








67 


1.5648 


54.63 


33 


1.2409 


26.91 






i 



APPENDIX. 



721 



TABLE IV. 

Dr. lire's Table of the Quantity of Real or Anhydrous Nitric Acid in 100 
Parts of Liquid Acid at different Densities, 



Specific 


Real Acid 


Specific 


Real Acid 


Specific 


Real Acid 


Gravity. 


iti 100 parts. 


Gravity. 


in 100 parts 


Gravity. 


in 100 parts 




of the Liquid 




of the Liquid. 




of the Liquid. 


1.5000 


79.700 


1.3783 


52.602 


1.1895 


26.301 


14980 


78.903 


1.3732 


51.805 


1.1833 


25.504 


1.4960 


78.106 


1.3681 


51.068 


1.1770 


24.707 


1.4940 


77.309 


1.3630 


50.211 


1.1709 


23.910 


1.4910 


76.512 


1.3579 


49.414 


1.1648 


23.113 


1.4880 


75.715 


1.3529 


48 617 


1.1587 


22.316 


14850 


74.918 


1.3477 


47.820 


1.1526 


21.519 


1.4820 


74.121 


13427 


47.023 


1.1465 


20.722 


1.4790 


73.324 


,1-3376 


46.226 


1.1403 


19.925 


1.4760 


72.527 


1.3323 


45.429 


1.1345 


19.128 


14730 


71.730 


13270 


44632 


1.1286 


18.331 


1.4700 


70.933 


1.3216 


43.835 


11227 


17.534 


14670 


70.136 


1.3163 


43.038 


1.1168 


16.737 


1.4640 


69.339 


1.3110 


42.241 


1.1109 


15.940 


1.4600 


68.542 


1.3056 


41.444 


1.1051 


15.143 


1.4570 


67.745 


1.3001 


40.647 


1.0993 


14346 


1.4530 


66.948 


1.2947 


39.850 


1.0935 


13.549 


1.4500 


66.155 


1.2887 


39.053 


1.0878 


12.752 


1.4460 


65.354 


1.2826 


38.256 


1.0821 


11.955 


1.4424 


64.557 


1.2765 


37.459 


1.0764 


11.158 


1.4385 


63.760 


1.2705 


36.662 


1.0708 


10.361 


1.4346 


62.963 


1.2644 


35.865 


1.0651 


9.564 


1.4306 


62.166 


1.2583 


35068 


1.0595 


8.767 


1.4269 


61.369 


1.2523 


34271 


1.0540 


7.970 


1.4228 


60.572 


1.2462 


33.474 


1.0485 


7.173 


1.4189 


59.775 


12402 


32.677 


1.0430 


6.376 


1.4147 


58.978 


1.2341 


31.880 


1.0375 


5579 


1.4107 


58.181 


1.2277 


31.083 


1.0320 


4.782 


1.4065 


57.384 


1.2212 


30.286 


1 0267 


3.985 


1.4023 


56.587 


1.2148 


29.489 


1.0212 


3.188 


1.3978 


55.790 


1.2084 


28 692 


1.0159 


2 391 


1.3945 


54.993 


1.2019 


27-895 


1.0106 


1.594 


1.3882 


54.196 


1.1958 


27.098 


1.0053 


0.797 


1.3833 


53.399 











61 



722 



APPENDIX. 



TABLE V. 

Table of M. Lowitz, showing the Quantity of absolute Alcohol in Spirits of 
different Specific Gravities. 



100 Parts. 


Sp. Gravity. 


100 Parts. 


Sp. Gravity. t 


100 Parts. 


Sp. Gravity. 


Ale. 


Wat. 


At 60°. 


At 68". 


Ale. 


Wat. 
34 


At 60 . 


At 68o. 


Ale. 
32 


Wat. 
68 


At 60". 


At 6fco. 


100 





0.796 


0.791 


66 


0.881 


0.877 


0.955 


0.952 


99 


1 


0.798 


0.794 


65 


35 


0.883 


0.880 


31 


69 


0.957 


0.954 


98 


2 


0.801 


0.797 


64 


36 


0.886 


0.882 


30 


70 


0.958 


0.956 


97 


3 


0.804 


0.800 


63 


37 


0.889 


0.885 


29 


71 


0.960 


0.957 


96 


4 


0.807 


0.803 


62 


38 


0.S91 


0.887 


28 


72 


0.962 


0.959 


95 


5 


0.809 


0.805 


61 


39 


0.893 


0.889 


27 


73 


0963 


0.961 


94 


6 


0.812 


0.808 


60 


40 


0.896 


0.892 


26 


74 


0.965 


0.963 


93 


7 


0.815 


0.811 


59 


41 


0.898 


0.894 


25 


75 


0.967 


0.965 


92 


8 


0.817 


0.813 


58 


42 


0.900 


0.896 


24 


76 


0.968 


0.966 


91 


9 


0.820 


0.816 


57 


43 


0.902 


0.899 


23 


77 


0.970 


0-968 


90 


10 


0.822 


0.818 


56 


44 


0.905 


0.901 


22 


78 


0.972 


0.970 


89 


11 


0.S25 


0.821 


55 


45 


0.906 


0.903 


21 


79 


0.973 


0.971 


88 


12 


0.827 


0.823 


54 


46 


0.908 


0.905 


20 


80 


0.974 


0.973 


87 


13 


0.830 


0.826 


53 


47 


0.910 


0.907 


19 


81 


0.975 


0-974 


86 


14 


0.832 


0.828 


52 


48 


0.912 


0.909 


18 


82 


0.977 


0.976 


85 


15 


0-835 


0.831 


51 


49 


0.915 


0.912 


17 


83 


0.978 


0.977 


84 


16 


0-838 


0.834 


50 


50 


0.917 


0.914 


16 


84 


0.979 


0-978 


83 


17 


0-840 


0.S36 


49 


51 


0.920 


0.917 


15 


85 


0.981 


0-980 


82 


18 


0-843 


0.839 


48 


52 


0.922 


0.919 


14 


86 


0.982 


0-981 


81 


19 


0-846 


0.842 


47 


53 


0.924 


0.921 


13 


87 


W.984 


0-983 


80 


20 


0-848 


0.844 


46 


54 


0.926 


0.923 


12 


88 


0.986 


0-985 


79 


21 


0-851 


0.847 


45 


55 


0.928 


0.925 


11 


89 


0-987 


0-986 


78 


22 


0-853 


0.849 


44 


56 


0.930 


0.927 


10 


90 


0.988 


0-987 


77 


23 


0-855 


0.851 


43 


57 


0.933 


0.930 


9 


91 


0.989 


0-988 


76 


24 


0-857 


0.853 


42 


58 


0.935 


0.932 


8 


92 


0.990 


0.989 


75 


25 


0-860 


0.856 


41 


59 


0.937' 


0.934 


7 


93 


0.991 


0.991 


74 


26 


0-863 


0.859 


40 


60 


0.939 


0.936 


6 


94 


0.992 


0.992 


73 


27 


0-865 


0.861 


39 


61 


0.941 


0.938 


5 


95 




0.994 


; 72 


28 


0-867 


0.863 


38 


62 


0.943 


0.940 


4 


96 




0.995 


71 


29 


0-870 


0.866 


37 


63 


0.945 


0.942 


3 


97 




0.997 


70 


30 


0-872 


0.868 


I 36 


64 


0.947 


0.944 


2 


98 




0998 


69 


31 


0-874 


0.870 


I 35 


65 


0.949 


0946 


1 


99 




0.999 


68 


32 


0-875 


0.872 


j 34 


66 


0.951 


0.948 





100 




1.000 


67 


33 


0.S79 


0.875 


| 33 


67 


0.953 


0.950 




1 







TABLE VI. 

Tables showing the Specific Gravity of Liquids, at the Temperature of 55° 
Fahr. corresponding to the Degrees of Beaume's Hydrometer. 



10 : 

11 
12 
13 
14 
15 
16 



Sp.Gr. 

1.000 
.990 
.985 
.977 
.970 
.963 
.955 



For Liquids lighter than Water. 



Deg. Sp. Gr. 

17 = .949 



18 
19 
20 
21 
22 



.942 
.935 
.928 
.922 
.915 



D« 



Sp. Gr. 



23 = .909 



24 
25 
26 
27 

28 



.903 
.897 
.892 
.886 
.880 



Beg. 

29 : 

30 
31 
32 
33 
34 



Sp. Gr. 

= .874 
.867 
.861 
.856 
.852 
.847 



For Liquids heavier than Water. 



)eg. 


Sp. Gr. 


0= 


=1.000 


3 


1.020 


6 


1.040 


9 


1.064 


12 


1.089 



Deg. 


Sp. Gr. 


15 = 


= 1.114 


18 


1.140 


21 


1.170 


24 


1.200 


27 


1.230 



Deg. Sp. Gr. 
30 = 1.261 
33 1.295 
36 1.333 
39 1.373 
42 1.414 



Deg. Sp. Gr. 
45 = 1.455 
48 1.500 
51 1.547 
54 1.594 
57 1.659 



Beg. 
35 
36 
37 

38 
39 
40 



Sp. Gr. 

= .842 
.837 
.832 
.827 
.822 
.817 



Beg. Sp. Gr. 
60=1.717 
63 1.779 
66 1.848 
69 1.920 
72 2.000 



APPENDIX. 



723 



TABLE VII. 



TABLES FOR REFERENCE IN QUALITATIVE ANALYSIS, 



I. GASES. 

Distinctive properties of oxygen> nitrogen, protoxide of nitrogen, deutoxide 
of nitrogen, hydro gen> carbonic oxide and carbonic acid. 



Soluble in 

water. 

Support 
combustion 

Combustible < 

Extinguish 
combustion 



iguish S 
ustion J 



Carbonic acid 
Protoxide of nitrogen 
Oxygen 
Protoxide of nitrogen 

Carbonic oxide 

Hydrogen 

Deutoxide of nitrogen 

Nitrogen 



Solution disturbs lime-water. 
Does not. 



Product of combustion dis- 
turbs lime-water. 

Does not. 

Forms brown fumes with oxy- 
gen. 

Does not. 



II. ACIDS. 



Distinctive properties of certain acids, in combination. 



ACIDS. 



Sulphuric 

Precipitated j ^,p hurou8 
by chloride { p hn F snh ori C 



of barium 



Precipitated 
by nitrate 
of silver. 



Phosphoric 

Pyrophosphoric 

Carbonic 

Hyposulphurous 

Hydrochloric, 

Hydriodic 

Phosphoric 

Pyrophosphoric 

Iodic 

Carbonic 

Sulphurous 

Hyposulphurous 



white 
yellow 

»» 
white 



Precipitate not dissolved by 
nitric acid. 



Precipitate dissolved by hy- 
drochloric acid. 



Precipitate not dissolved by 
nitric acid. 



Precipitate dissolved by nitric 
acid. 



sulphur appears. 



724 



APPENDIX. 



Indicated by 
strong sul- 
phuric acid. 



ACIDS. 

Carbonic 
Sulphurous 

Hyposulphurous- 

Hydriodic 
Chloric 



Effervescence of a gas which 
renders lime-water turbid. 

Effervescence: gas decomposes 
iodic acid. 

Effervescence of sulphurous 
acid, and sulphur deposit- 
ed. 

Iodine liberated. 

Peroxide of chlorine evolved, 
and liquid bleaches. 



SPECIAL TESTS. 

Hydriodic acid, by chlorine-water and starch. 
Iodic acid, by sulphurous acid water and starch* 
Sulphurous acid, by iodic acid and starch. 
Nitric acid, by sulphate of indigo. 
Hyposulphurous acid dissolves chloride of silver. 

" " is not precipitated by nitrate of strontian. 



MI. ALKALIES AND EARTHS. 

Distinctive properties of potash, soda, ammonia, barytes, lime, strontian, mag- 
nesia and alumina, in their salts; the reagents to be applied in succession 
as numbered.. 



REAGENTS. 



1° Carbonate of soda 
2° Oxalate of ammonia 
3° Diluted sulphate of soda 
4° Hyposulphite of soda 



Precipitates earths and not alkalies. 
Precipitates barytes, strontian and lime. 
Precipitates barytes and strontian, but not lime. 
Precipitates barytes but not strontian. 



SPECIAL TESTS. 



Caustic potash evolves ammonia. 
Tartaric acid in excess precipitates potash. 
Bicarbonate of potash does not precipitate magnesia. 
Caustic potash dissolves alumina. 



APPENDIX. 



125 



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APPENDIX. 



TABLE VIII. 

SELECTED ATOMIC WEIGHTS, WITH THEIR LOGARITHMS, FOR 
THE CALCULATIONS OF ANALYSIS. 

The numbers are the same as those given in the body of the work (from Berzelius,) with 
the exception of carbon, which is always taken here at 75, (Dumas,) and nitrogen at 175.6; 
the last deduced by Dr. Clark from M. Dumas' recent determinations of the densities of 
nitrogen and oxygen. 



Name. 


Symbol. 


Atomic Weight. 


Logarithm. 


Ammonia 


NH S 


21&13 


2.32864 


Antimony 


Sb 


1612.9 


3.20761 


(oxide of ) . 


Sb0 3 


1912.9 


3.28169 


(sulphuret of) . 


SbS 3 


2216.4 


3.34565 


Arsenic 


As 


940.1 


2.973174 


(sulphuret of ) . 


AsS, 


1543.6 


3.18854 


(sulphuret of ) . 


AsS 3 


1945.9 


3.28912 


Arsenic acid 


AsO s 


1440.1 


3.15839 


Arsenious acid 


As0 3 


1240.1 


3.09346 


Barium 


Ba 


856.88 


2.93292 


(chloride of) 


BaCl 


1299.5 


3.11378 


Barytes 


BaO 


956.88 


2.98086 


(carbonate of) . 


BaO,C0 2 


1231.9 


3.09058 


(phosphate of) . 


2BaO,P0 5 


2806.1 


3.44811 


(sulphate of) 


BaO,S0 3 


f 1458.1 


3.16379 


Calcium, chloride of 


CaCl 


698.67 


2.84427 


Carbon 


C 


75.00 


1.87506 


Carbonic acid 


C0 2 


275.00 


2.43933 


Carbonic oxide 


CO 


175.00 


2.24304 


Copper 


Cu 


395.70 


2.59737 


(protoxide of) . 


CuO 


495.70 


2.69522 


(suboxide of) 


Cu 2 


891.39 


2.95007 


Hydrogen 


H 


12.48 


1.09621 


Iron .... 


Fe 


339.21 


2.53047 


(peroxide of) 


Fe 2 3 


978.4a 


2.99053 


(protoxide of) 


FeO 


439.21 


2.64267 


Lead .... 


Pb 


1294.5 


3.11210 


(carbonate of) 


PbO,C0 2 


1669.5 


3.22259 


(chloride of) . 


PbCl 


1737.1 


3.23983 


(phosphate of) 


2PbO,P0 5 


3681.3 


3.56600 


(protoxide of ) 


PbO 


1394.5 


3.14442 


(sulphate of) 


PbO,S0 3 


1895.7 


3.27777 


Lime .... 


CaO 


356.02 


2.55147 


(carbonate of) 


CaO,C0 2 


631.03 


2.80004 


(sulphate of) 


CaO,S0 3 


857.19 


2.93308 


Magnesia 


MgO 


258.35 


2.41220 


(sulphate of) . 


MgO,S0 3 


759.52 


2.88054 


Manganese . 


Mn 


345.90 


2.53895 


(protoxide of) . 


MnO 


445.90 


2.64924 


(deutoxide of) . 


Mn 2 3 


991.80 


2.99642 


Mercury 


Hg 


1265.8 


3.10236 


(subchloride of) . 


KHg 2 Cl) 


1487.1 


3.17234 


(oxide of) . 


HgO 


1365.8 


3.13539 


(suboxide of) . 


Hg.O 


2631.6 


3.42022 



APPENDIX. 



727 



Name. 


Symbol. 


Atomic Weight. 


Logarithm. 


Nitrogen 


N 


175.6 


2.24452 


Phosphoric acid . 


P0 5 


892.31 


2.95052 


Phosphorous acid . 


PO, 


692.21 


2.84030 


Phosphorus . 


P 


392 31 


2.59363 


Platinum 


Pt 


1233.3 


3.09107 


(ammonium chlo- 
ride of ) . 


JPt,Cl 2 +? 
\ NH 4 C1 ] 


2786.5 


3.44506 


(potassium chlo- 








ride of ) . 


PtCl 2 +KCl 


3051.2 


3.48447 


Potash 


KO 


569.92 


2.77079 


(carbonate of) . 


KO,C0 2 


864.93 


2.93698 


(sulphate of) 


KO,S0 3 


1091.1 


3.03786 


Potassium 


K 


489 92 


2.69013 


(chloride of) 


KC1 


932.57 


2.96968 


Silver .... 


Ag 


1351.6 


3.13085 


(chloride of ) . 


AgCl 


1794.3 


3.25389 


(oxide of) 


AgO 


1451.6 


3.16185 




—2 


29032 


3.46288 




—3 


4354.8 


3.63897 




—4 


5806.4 


3.76391 




—5 


7258.0 


3.86082 


Soda .... 


NaO 


390.90 


2.59207 


(carbonate of) 


NaO.CO, 


665 91 


2.82341 


(sulphate of ) • 


NaO,S0 3 


892.07 


2.95040 


Sodium 


Na 


290.90 


2.46374 


(chloride of) 


NaCl 


733.55 


2.86543 


Strontian 


SrO 


647.29 


2.81110 


(carbonate of) . 


SrO, C0 2 


922.30 


2.96487 


(sulphate of) 


SrO,S0 3 


1148.50 


3.06013 


Strontium, chloride of . 


SrCl 


999.94 


2.99561 


Sulphur 


S 


201.17 


2.30356 


Sulphuric acid 


S0 3 


501.17 


2.69998 


Sulphurous acid . 


SO. 


401.17 


2.60333 


Tin ... . 


Sn" 


735.29 


2.86645 


(peroxide of ) . 


Sn0 2 


935.29 


2.97095 


(protoxide of) 


SnO 


835.29 


2.92184 


Water .... 


HO, 


112.48 


2.05107 




2 


224.96 


2.35210 




3 


337.44 


2.52820 




4 


449.92 


2.65314 




5 


562.40 


2.75005 




6 


674.88 


2.82923 




7 


787.36 


2.89618 




8 


899.84 


2.95417 




9 


1012.3 


3.00531 




10 


1124.8 


3.05107 




11 


1237.3 


3.09248 




12 


1349.8 


3.13027 




13 


1462.2 


3.16501 


Zinc .... 


Zn 


403.23 


2.60555 


(oxide of) 


ZnO 1 


503.23 


2.70177 




2 


1006.5 


3.00281 




3 


1509.7 


3.17889 




4 


2012.9 


3.30382 



728, 



APPENDIX. 



TABLE IX. 



ELECTRO-CHEMICAL DISTRIBUTION 



OF THE 



ELEMENTS. 



Electro- positive. 


Electro-negative. 


Oxygen. 


Mercury. 


Fluorine. 


Palladium. 


Chlorine. 


Silver. 


Bromine. 


Copper. 


Iodine. 


Lead. 


Sulphur. 


Tin. 


Selenium. 


Bismuth. 


Tellurium. 


Cobalt. 


Nitrogen. 


Nickel. 


Phosphorus. 


Iron. 


Arsenic. 


Manganese. 


Antimony. 


Cadmium. 


Silicon. 


Zinc. 


Boron. 


Hydrogen. 


Columbium. 


Carbon. 


Tungsten. 


Didymium. 


Molybdenum. 


Lantanum. 


Gold. 


Cerium. 


Titanium. 


Zirconium. 


Platinum. 


Aluminum. 


Osmium. 


Thorium. 


Uranium. 


Ittrium. 


Rhodium. 


Glucinum. 


Iridium. 


Magnesium. 


Vanadium. 


Calcium. 


Chromium. 


Strontium. 




Barium. 




Lithium. 




Sodium. 




Potassium. 



INDEX. 



Absorption, 689. 

Acetal, or compound of aldehyde with 

ether, 532. 
Acetate of alumina, 535. 

of barytes, 534. 

of ammonia, 534. 

of black oxide of mercury, 451. 

of copper, 406. 

of lead, 412. 

of oxide of ethyl, 534. 

of lime, 534, 

of magnesia, 535. 

of morphia, 662. 

of potash, 534. 

products of the action of heat upon, 540. 

of soda, 534. 

of etrontian, 534. 
Acetone, 486, 540. 

(met-), 541. 
Acetyl, series of compounds, 531. 

acetate of oxichloride of, 535. 

hydrate of the oxide of, 531. 

oxisulphuret of, 535. 

action of chlorine, bromine and iodine 
upon ethyl. 535. 

chloride of, 536, 539. 

hydruret of, 538. 

chlorhydrate of chloride of, 539. 

chloroplatinates of chloride of, 539, 540. 

bromide of, 539. 

bromhydrate of bromide of, 539. 

iodhydrate of iodide of, 539. 

arsenical compounds derived from, 543. 

series of compounds of amidogen, tables 
547, 549. 
Acid, acetic, 533. Its combinations, 534. 
Action of heat upon, 492, 540. 

acetous or aldehydic, 532. 

aconitic, 640. 

althionic, 531. 

alloxanic, 679. 

amygdalic, 577. 

antimonious, 442. 

anthranilic, 623. 

arsenic, 434. 



Acid, arsenious, 121, 126, 433. 
antidote to arsenious, 391, 439. 
azelaic, and others, 654. 
benzilic, 503, 586. 
benzoic, 577. 
boraCic, 155, 229. 
bromic, 274. 
brornobenzoic, 502. 
brunolic, 572. 
butyric, 646. 
cacodylic, 544. 
cafTelc, 611. 
capric, 544. 
caproic, 646. 
carbazotic, 622. 
carbolic, 572. 
carbonic, 224. 
cevadic, 647. 
chloracetic, 492, 537. 
chloranilic, 623. 
chloric, 266. 
chlorous, 269. 
chlorocarbonic, 272. 
chlorisatinic, 503, 622. 
chlorisatidic, 622. 
chlorochromic, 425. 
chloromolybdic, 430. 
ehlorosulphuric, 242,. 
chlorotungstic, 428. 
chromic, 423. 
chrysanilic, 623-. 
cinnamic, 588. 
citraconic, 640. 
citric, 639. 
comenic, 635. 
cocinic, 648. 
croconic, 633. 
crotonic, 647. 
cuminic, 608. 
cyan uric, 670, 67& 
cyanic, 500, 670, 673. 
delphinic, 647. 
ellagic, 638. 
eladic, 654. 
erythroleic, 625. 



730 



INDEX, 



Acid, etherosulphuric, 524. 
ethalic, 598, 649. 
ethionic and isethionic, 530. 
euchronic, 634. 
ferric, 122. 
ferricyanic, 500, 670. 
ferrocyanie, 500, 669. 
formic, 563 to 566. 
formobenzollic, 508* 
of fruits, 644, &c. 
fulminic, 670, 673. 
fu marie, 645. 

fuming, of Nordhausen, 238. 
gallic, pyrogallic, metagallic, and me- 

langallic, 637. 
hippuric, 580. 
hircic, 647. 
hydriodic, 279. 
hydrobromic, 274. 
hydrocyanic, 667. 
hydrochloric, 262. Preparation of, 

283. 
hydrofluorc, 283. 
hydroleic, 656. 
hydromargaric, 656. 
hyperchloric, 267. 
hyperiodic, 281. 
hypermanganic, 121. 
hypochlorous, 265. 
hypomargarylic, 656. 
hypophosphorous, 249. 
hyposulphuric, 244. 
hyposulphurous, 241. 
indigotic, 622. 
iodic, 279. 
itaconic, 640. 
japonic, 638. 
lactic, 550, 551. 
lignin-sulphuric, 518. 
malic, 644. 

margaric, 649, 651, 655. 
meconic, 634. 
melassic, 515. 
melitic, 633. 
methionic, 531. 
metoleic, 656. 
molybdic, 429. 
mucic, 515. 
muriatic, 262. 
naphtalic, 575. 
nitric, action upon copper, 213. Its 

preparation, 217. Its properties, 213. 

et seq. Neutral nitrates, 219. Uses 

of the acid, 220. 
nitrosulphuric, 243. 
nitrous, 121, 215, 216. 
oleic, 653. 
oleophosphoriGj 713. 
osmic, 475. 
oxalic, 631. 
oxalovinic, 529.. 
palmitic, 648. 



Acid, parabanic, 679. 

paratartaric or racemic, 643. 

pectic, 599. 

phocenic, 647. 

phosphoric, 116, 251. 

picrie, 622. 

pi marie, 605. 

platinocyanic, 670. 

prussic, 667. 

pyromaric, 605. 

pyromeconic, 635. 

pyrotartaric, 643. 

quinic or kinic, 645. 

rhodizonic, 632. 

roccellic, 625. 

rosolic, 572. 

saccharic, 512. 

sacchulmic, 515. 

salicylous, 502, 591. 

sebacic, 654. 

selenic, 246. 

selenious, 245. 

sericic, 648. 

stearic, 650. 

suberic, 518, 652. 

succinic, 652. 

sulpha ntimonic, 443* 

sulpharsenious, 435. 

sulpharsenic, 435. 

sulphate of oxide of ethyl, 524. 

sulphosaccharic, 514. 

sulphonaphtalic, 573. 

sulphonaphtic, 573. 

sulphovinic, sulphethylic, &c.,,524. Its- 
formation, 525. 

sulphomesitilic, 542. 

sulphocymenic, 608. 

sulphurous, 234, 503. 

liquid sulphurous, 28, 235. 

series of the sulphurous, 236. 

sulphuric, 236, 655. 

anhydrous sulphuric, 238. 

properties of the sulphuric, &c., 238. 

hydrates of sulphuric, 239. 

tannic, 137, 635. 

tartaric and paratartaric, 640, et seq. 

tungstic, 427. 

valeric or valerianic, 555. 

vanadic, 426. 

veratric, 647. 

xanthic, 529. 

xylitic, 569. 

compounds, definitions of, 89. 

nomenclature of, 90. 

those containing carbonic oxide, 631. et 
seq. 

of castor oil, 655. 

action of sulphuric, on the fat oils, 655^ 

formation of, 119, 502i 
Aconitic acid, 664. 
Aconitine, 982. 
Aconitura napellus, acid of, 487, 640^ 



INDEX. 



731 



Acroleine, 656. 
Adhesion, 145. 
Affinity, of chemical, 145. 
order of, 149. 
modified by volatility, 150. 

by insolubility, 151. 
inductive, 156, et seq. 
Air, atmospheric, 68, 684. 

movement of masses of, produced by 

inequality of temperature, 206. 
atmospheric vapour, 207. Analysis of 
the air, 208. 
Albite or soda felspar, 364. 
Albumen, vegetable, 509,618,688. 

animal, 688, 690. 
Albuminous ferments, 550. 
Alcargen, 544. 

Alcarsin, or liquor of cadet, 543, 544, 545. 
Alcoates, crystalline, compounds of alco- 
hol with various salts, 520 
Alcohol, 119. Distilled from liquids after 
vinous fermentation, 519. 
type, 499. 
absolute, 519, 520. 
its compounds, 520. 
products of its combustion, 520. 
congeners of, (of an uncertain constitu- 
tion,) 538, et seq. 
mesitic, 540. 
amilic, 554. 
Aldehyde, 486, 531, 
its type, 490. 
ammonia. 532. 
(met-), 532. 
mesitic, 542. 
resin of, 532. 
Algaroth, powder of, 441. 
Alkalimetry, and the alkalimeter, 329, 

353. 
Alkaline earths, their metallic bases, &c, 
119, 120, 342, 650. 
reaction, neutralized, 330. 
Alkalies, of 329. et seq. 
[See sodium, potassium, &c] 
Alkalies, veseto-, 656. 
Alizarin. 626. 
Allantoic 501, 678. 
Alloxan, 678. 

Alloxantin, 680, dimorphous, 681. 
Alloy, white, of nickel, 397, 399. 
Alloys of bismuth, 415. 
of cadmium, 402. 
of copper, 406. 
of gold, 464. 
of lead and tin, 412. 
of silver, 463. 
of tin, 419. 
of zinc, 401. 
Almonds, oil or essence of bitter, 486, 502 
579. 
constituents of, 587. 
the white of (sweet and of bitter,) 586 



Alum, 361. et seq, burnt, 362. 
ammoniacal, 161, 363. 
soda, 363. 

salts isomorphous with, 363. 
chrome, 422. 
iron, 393. 
slate, 362. 

stone of the Roman states, 362. 
Alumina, acetate of, 535. 
hydrate of, 359. 
salts of, 361, 
sulphate of, 361. 
sulphate of potash and, 361. 
nitrate of, 363. 
silicates of, 364. 
insoluble phosphate of, 363. 
mellitate of, 634. 
Aluminum, its class, 119. 
anhydrous chloride of, 560. 
fluoride of, 361. , 
sulphocyanide of, 361. 
sulphuret of, 360. 
Amarythrin, 624. 
Amber, 614. 
Amblygonitc, a phosphate of alumina and 

litlna, 364. 
Amides, 144. 

Amidin, or gelatinous starch, 505. 
Amidogen and amides, 144, 290. 

tables of the corresponding compounds 
of acetyl, and, 547, 549. 
Ammeline, 676. 
Ammelide, 676. 
Amilene, 556. 
Ammonia, 291, 657, 684. 
oxal urate of, 6S1. 
alum, 116, 363. 
acetate of, 534. 
bichloride of tin and, 419. 
chloride of mercury and, 452, 499. 
with anhydrous salts, 294. 
hydrochlorate of, 294. 
carbonic acid and, 293. 
in solution, 292, 293. 
molecular formula of, 499. 
neutral mellitate of, 634. 
oxalate of, 632. 

phosphate of magnesia and, 357. 
compounds of cyanic acid and, 671. 
salts of, 142, 293,295. 
sulphate of, 293, 296. 
neutral tannate of, 636. 
Ammoniated salts, 295. 
Ammoniacal gas, 291. 
Ammoniacal alum, 363. 
Ammoniaret of silver, 460. 
Ammonio-nitrate of silver, 436. 

sulphate of copper, 437. 
Ammonium, 120, 143, 294. 
its chloride, &c, 294, et seq. 
theory, 143. Salts of, 295. 



732 



INDEX. 



Ammonium, and ethyl series, on the rela- 
tion between them, 546 to 549. 
Amphibole or hornblende, 357. 
Amphigen or leucite, 364. 
Amygdalates, the, 577. 
Amygdalic acid, 577. 
Amygdalin, 156, 576. 

bodies derived from its decomposition, 
576, 587, et seq. 
Amyl, 552. 

series of compounds, 552. Table 554, 

vinous, 59. 

bromide of, 554. 

hydrate of oxide of, 554. 

iodide of, 554. 

chloride of, 554., 

chlorinated chloride of. 554. 

sulphates of oxide of, 554, 555. 

acetate of oxide of, 555. 

chlorinated acetate of oxide of, 555. 
Amylaceous and saccharine substances, 

504. 
Amylene, bihydrate of, 554. 
Analcime, 364. 
Analyses of, 95. 
Analysis of organic compound substances, 

479. 
Animals, food of, 685. 
Anhydrite, mineral, 350. 
Animalculse of stagnant water, 690. 
Anilic acid, 622. 
Aniline, 623. 
Animal charcoal, 223. 

fat, 649, 685. 

organization, 496; processes, 683. 

substances, salts produced by potassium 
and, 665. 

secretions, 703 to 710. 

solid parts, 711, et seq. 

heat, 687. 
Anthiarin, 617. 

Anthracite a nearly pure carbon, 222. 
Antimoniate of potash, 442. 

of soda, 442. 
Antimonic acid, 442. 
Antimonious acid, 442. 
Antimony, 121, 439. 

sulphurets of, 440, 443. 

oxide of, 440. 

chloride of, 441. 

pentachloride of, 443. 

sulphate of, 441. 

precipitated sulphuret of, 125, 440. 

and potash, the oxalate of, 441. 

the tartrate of, 441. 
Ants, red ; and formic acid, &c, 563. 

artificial oil of, 566. 
Apatite, 350. 

Apples, and their acid, 644. 
Archil weed, 624,. 

of commerce, 624. 
Aricine, 660, 664. 



Arragonite, 117, 125. 
Arrangement, chemical, 129. 
Arrow-root, from the marantha arundina- 

cea, 505. 
Arseniates and phosphates isomorphous, 

116. 
Arseniates of the earths and alkalies, 434. 

of silver, 435. 
Arsenic, its characters and properties, 433. 
Arsenic, its classification, 121. 

acid, 434. 

bromide of, 435. 

chlorides of, 435. 

fluoride of, 435. 

iodide of, 435. 

sulphurets of, 435. 

reduction of the sulphuret of, 437. 

tests and testing for, 436. 

and hydrogen, 435. 

solid arseniuret of hydrogen, 435. 
Arsenious acid, 121,433. 

tests of, 436, et seq. 

antidotes for, 391, 439. 

phenomenon observed during its crys- 
tallization, 126. 
Arteries, middle coat of the, 701. 
Asparagin, 616. 

Atmosphere, the, 204. Temperature of 

the, 205. Blue colour of the sky, 205. 

Winds, 206. Mean pressure of the 

atmosphere, 55, 204, et seq^ 

Atmospheric air, weight of the oxygen 

and nitrogen in, 209. 
Atomic theory, 103, 498. 

weights, 103. Definition of, 103. 
Atoms of the elementary bodies, how re- 
presented, 103. 

specific heat of, 105- 

relation between the weight and volume 
of, 107. 
Atropine, 660, 664. 
Augite, 357. 

Attraction, electrical and magnetical re- 
pulsion and, 161. 
Aurate of ammonia, &c, 465. 

of potash, 465. 
Auric oxide, 465. 
Aurum, see Gold, 464. 
Aurum musium, 418. 
Azoerythrin, 625. 
Azolitmin, 635. 
Azote, protoxide of, 211. 

deutoxide of, 213. 
Azotic acid, 217. 
Azotous acid, 215. 

Balsams of Peru, Tolu, &c, 590. 
Barium, 342. Its classification with stron- 
tium and lead, 120. 

chloride of, 343. 

peroxide of, 343. 
Bark, gray, 662. 



INDEX. 



733 



Bark, yellow, 662. 

quinquina, 665. 
Barley-sugar, transparency of, 52. 
Barytes, 342. 

the hydrate of, 342. 

solution of, 343. 

chlorate, &c. of, 344. 

carbonate of, 344. 

sulphate of, 344. 

nitrate of, 344. 

isethionate of, 530. 

oxalate of, 632. 
Bases, chemical, 116. Law of their com- 
binations with acids, &c, 133. 

organic, 656, et seq. 
Basic salts of lead, 640, et passim. 
Beer, Bavarian, 533. 
Benzamide, 502, 530. 
Benzilate of potash, 503> 
Benzile, 503, 586. 
Benzilic acid, 586* 
Benzimide, 585. 
Benzin or benzole, 486, 583. 
Benzoate of peroxide of iron, 394* 
Benzoates, the, 578, 580. 
Benzoic acid, 577. 
Benzoine, 585. 

Benzoyl or benzoile series of compounds, 
577. 

products of the decomposition of, 581. 

hydruret of, 579. 

products of the decomposition of, 584. 
Berberin, obtained from roots of the bar- 
berry, 630. 
Beryl, 368. 
Binary theory, the, 130, 498. 

objections to the, 132, 141. 
Bismuth, general account of, 413. 

the suboxide, 413. 

protoxide, sulphuret, chloride, sulphate 
of the oxide, and nitrate of, 120, 414. 

subnitrate, magistery, and peroxide of, 
414. 

the alloys of, 415. 
Bitter of Welter, 622. 
Bittern of sea-water, 328. 
Bitumen, of, 575. 
Bile and biliary secretions, of, 704. 

sugar, 704. 
Biliary matter, 705. 
Bilin, 704. 
Biliverdin, 706. 
Black lead, 221. 

Bleaching acids and compounds, 351. 
Bleaching powder, 350, et seq. 
Blood, and animal secretions, 156, 496, 
687. 
calcined, 665, 666. 
pure serum of, 608. 
constitution of the, 794. 
Blue basic Prussian, 393. 
copper ore, 404. 
62 



Blue, Prussian, precipitated with a salt of 
iron, &c, 388, 393, 668, 669, 670. 

Turnbull's, 388, 670. 
Boilers, various forms of, 62. 
Boiling temperature of liquids, 54. 
Boneblack, 223. 
Bones, of the, 710. 
Boracic acid, liberated, 155, 229. 
Boracite, mineral, 357. 
Borate of soda, 155, 229. 

of magnesia, 357. 

of lime and magnesia, double, 357. 
Borax, 155. 
Boron, and boracic acid, 122, 223, 229. 

fluoride of, 229, 285. Chloride of, 272. 
Brain, substance of the, 711. 
Breezes, land and sea, 206. 
Brewing, process of, 509. 
Brezilin, colouring matter of Brazil wood. 

629. 
Bromal, 533. 
Bromide of carbon, 275. 

of phosphorus, 275. 

of silicon, 275. 

of sulphur, 275. 
Brominated ether, 533. 
Bromine, the element, 121, 273. 

its preparation, 273. 

properties of, 274. 

chloride of, 275. 

action of, upon ethyl, acetyl and their 
compounds, 535. 

compounds of formyl with, 566. 
Brucine, 659, 663. 
Brunolic acid, 572. 
Butter, volatile acids of, 646. 

of cocoa, nutmegs, etc., G4^. 

butyrous qualities in milk, 709. 
Butyrone, 646. 

Cacodyl, 543. 

chloride of, 545. 

cyanide of 545. 

oxide of, 544, 545. 

sulphurets, 544. 
Cacodylic acid, 544. 
Cadet, liquor of, 543. 
Cadmia fossil is, 401. 
Cadmium, of, 401. 

oxide of, and sulphuret of, 116, 401. 

definite alloys of, 402. 
Caffeic acid, 618. 
CafPein, obtained from coffee, 617. 
Cajeput oil, 608. 
Calamine, 399. 
Calc-spar, 116, 117. 
Calcium the basis of lime, 346. 

chloride of, 348, 559. 

sulphurets of, 348. 

fluoride of, 348. 

peroxide of, 347. 

phosphuret of, 348. 



734 



INDEX. 



Calomel, 449. i 

black compound by solution of ammonia 
with, 450, 499. 
Camomile, oil of, 609. 
Camphogen, 610. 
Camphor, of, 610. 
Caoutchine, 613. 
Caoutchouc, passage of gases through a 

sheet of, 74. 
Capillary action, 71. 
Capnomor, 572. 
Caramel, 512. 
Carbamide, 291. 

Carbon, general description of, 221, et 
seq. 
its class, 122. 
chlorides of, 270. 
and hydrogen, 299. 
tisulphuret of, 117, 303. 
of plants, 210. 
Carbonic acid of the atmosphere, 209, 
684. 
acid, 224. 
Carbonic acid, fluid, 28, 66, 225. 

oxide, 227, said to be contained in acids, 
631. 
Carthamin, 628. 
Cassava, 505. 

Casein, 688. Also caseum, or coagu- 
lated milk, 693. 
vegetable, 689. 
Caseous principle, and cheese, 709. 
Cast iron, 383. 

white, 384. 
Castor oil, and its acids, 655. 
Catalytic agents, 155, 494. 
Catalysis or decomposition by contact, 

155, 494. 
Catalytic force explained, 155, 156. 
Catechin, 638. 
Catechu, 638. 
Cedriret, 572. 
Celestine, 345. 
Cement, Roman, 347. 
Centaurium minorius, 496. 
Cerebric acid, 713. 
Cerium, formiate of, 565. 
Ceruse or white lead, 410. 
Cetene, 598. 
Cetyl series of compounds, 597. 

hydrate of oxide of, 597. 
Cevadic acid, 647^ 
Chabasie, mineral, 120. 
Chains, polar, repulsed by each other, 161, 

&c. 
Charcoal, and its varieties, 222, et seq. 

crystalline forms of, 117. 
Chelidonine, 659, 664. 
Chemical affinity, 145, et seq. 

nomenclature and notations. Table i, 
86. Table ii, 87. Table iii, 88. 



Chemical terms, comparison of some old 
and new, 131. 
theory, 145. 
types, 490, 493, et seq. 
pneumatic, 70, &c. 
China-clay or kaolin, 364. 
Chloracetic acid, 537. 
Chloric acid, 266. 
Chlorates, 267. 
Chlorous acid, 269. 
Chloral, a fluid oleaginous liquid, 536. 
hydrate of, 537, insoluble, 537. 
mesitic, 542. 
Chloranile, 622. 
Chlorhydric acid, 262. 
Chlorides, 261, 454, 559, 566. 

[see the substances and metals nomina- 
tim.~\ 
Chlorimetry, experiments in, 352. 
Chlorine, a simple substance, 256. Its 
class and affinities, 121, 257. Pro- 
cess for its preparation, 257. 
its compounds with other elements, 

90, with lime, 350. 
its classification with iodine, bromine 

and fluorine, 121. 
properties of, 259. 
uses of, 260. 
its action upon ethyl, acetyl and their 

compounds, 535. 
its action upon oxide, and upon chlo- 
ride of methyl, 568. 
its substitution for hydrogen, 490. 
Chlorisatin, 503, 622. Bichlorisatin, 622. 
Chlorisatinic acid, 503, 622. 
Chlorisatyde and Bichlorisatyde, 622. 
Chloroid, the term, 169. 
Chloromenthene, 609. 
Chloronaphtalese, chlorhydrate of chloro- 

naphtalase, &c. 573. 
Chlorophyl, 615. 
Chlorosalicylirnide, 502. 
Chlorous attraction, 161. 
or negative elements, 498. Their or- 
der, 499. 
Chloroxalic ether, and compounds derived 

from it, 492. 
Cholesterin, 706. 
Cholic acid, 705. 
Cholinic acid, 706. 
Chondrin, 700. 
Chromate of lead, 424. 

the subchromate of lead, 424. 
of silver, 425. 
of magnesia, 425. 
of soda, 424. 

of potash, yellow and red, 424. 
the terchromate, 624. 
Chrome alum, 363, 422. 
Chrome iron, 423. 
Chrome yellow, 424. 



INDEX. 



735 



Chromic acid, 423. 
Chromium of, 421, et seq. 
oxide of, 116, 421. 
the hydrated oxide, 422. 
sesquisulphuret of, 422. 
sesquichloride of, 422. 
sesquicyanide of, 670. 
sulphate of, 422. 
oxalate of potash and, 423. 
terfluoride of, 425. 
salts of the oxide of, 120, 422. 
Chronometers, balance-wheel of, 27. 
Chrysene, 572. 
Chrysoberyl, 368. 
Chyle and chyme, 704. 
Cinchona, bark of, 662. 
Cinchonine, 659, 662, 663. 
Cinnabar, 451. 
Cinnamic acid, 588. 
Cinnamon oil, or essence of, and bodies 

derived from it, 588. 
Cinnamyl, and its series of compounds, 

588. 
Citrates of silver, copper, lead, &c. 640. 
Citric acid, its decomposition by heat, 487. 

products of its decomposition, 639. 
Classification of elementary bodies, L19, 

et seq. 
Clay, varieties of; silicates of alumina, 

364. 
Climates, 205, et seq.. 
Clouds, colours of the, 206. 

origin of, 207. 
Cloves, oil of, 82, 607. 
Coal, products of the distillation of, viz: 
leucol, pyrrol, naphtaline, &c. 572. 
caking-, cannel, wood, 489. 
gas, 73, 301, 489. 
Cobalt of, 395. 

the oxide zaffre, 395. 
protoxide, 395, phosphate, &c. of, 396. 
sulphurets of, 397. 
the cyanides of, 670. 
Cobalticyanide of potassium, 670. Cobal- 

ticyanogen, 670. 
Cocinic acid, 648. 
Cocoa, 648. 
Codeine, 659, 662. 
Cohesion, force of, 145. 
Colchicine, 664. 
Cologne, eau de, 601. 
Colophony, or resin of turpentine, 604. 
Colouring matters, neutral 619, 623, 626. 
Columbium, 446. 
Combination of chemical substances, &c. 

148, et seq. 
Combination, laws of chemical, 96, et seq. 
Combining proportions, 86, 87, 88, 92, 95. 
Combustion, principles of, 190. 
furnace for, 480. 
tube for, 479. 



Comenic acid, 635. 

Compounds, arrangement of elements in, 

129. 
Conduction of heat, 41, laws, 49. 
Coneine, conicine, or conia, 660, 664. 
Contact, of decomposition by, 155, et seq. 
Contagion, matters producing, 210. 
Copahuvic acid, 606. 
Copaiba, oil of, 606. 
Copper, or cuprum, 402. 

subchloride, &c. of, 403. 

protoxide of, 403. 

acetates of, 406. 

alloys of, 406. 

its chloride and carbonates, 404. 

isethionate of, 531. 

oxalate of, 632. 

oxalate of potash and, 406. 

sulphates of, 137, 404, et seq. 

ammonia-sulphate of, 405, 437. 

ammoniacal oxide of, 404. 

subsulphates of, 405. 

subsulphuret of, 120. 
Copperas, 389. 

class of sulphates, 137. 
Corrosive sublimate, 452. 
Corydaline, 660, 664. 
Coumarin, 618. 

Creosote and its compounds, 571. 
Croconate of lead, 633. 

of potash, 633. 
Croconic acid, 633. 
Crotonic acid, 647. 
Cryophorus of Wollasten, 66. 
Crystalline form and atomic constitution 
of bodies, their relation, 115, et seq. 
Crystallization of, 115, et seq. 

[see descriptions of the crystallization of 
various substances nominatim.] 
Cubebs of, from piper cubeba, 606. 
Cudbear, or persio, 626. 
Cuminic acid, 608. 
Cumyl or cuminol, 608. 
Curarine, or curara poison, 664. 
Cyamelide, 671. 
Cyanates, alkaline, 671, 672. 
Cyanic acid, 500, 670. 
Cyanides of silver, iron, potash, &c. 500, 
665, 669. 

of mercury, 455, 500, 669. 

double, 669. 

of hydrogen, 500, 667. 
Cyanogen, 304, 499, 665. 

compounds of, 90, 665, 670. 
Cyanol, 572. 
Cymene, 608. 

Daphnin, 618. 

Daturine, 664. 

Decomposition of animal matters, 700. 

Delphinine, 660, 664. 



736 



INDEX. 



Dew, deposition of, 48. 

Dextrin, or mucilaginous starch, 507. 

colourable or not colourable by iodine, 
508. 
Diabetic sugar, 513. 
Dialuric acid, 681. 
Diamond, the, 221. 

glazier's, 221. 
Diastase, a vegetable principle, 155, 

508. 
Dichroite, 365. 
Didymum, 446. 
Diffusion of gases, 70. 

of vapours, 75. 
Digestion, laws of, 687, et seq. 707. 
Disability of fluids, 28. 
Dilatation of solids by heat, 26. 

of liquids, 28. 

of gases, 31. 
Dimorphism, 124. 
Dislysin, 705. 
Disthene,.364. 

Distillation, 63. Engravings illustrative 
of, 63, 64. 

dry, 487. 

with an alkali, 486. 
Dolomite, a magnesian limestone, 355. 
Drying of, 78. Illustration of a drying- 
stove, 79. 
Dry rot, 518. 

Ductility of metals, 52, 307. 
Dutch liquid, 501. 
Dyeing, use of alum in, 363, 629, 

lichens, used in, 623. 

madder for, 627. 

use of logwood for, 629. 

Brazil wood, 629. 

Earth's temperature, the 49, 

Earthenware and pottery, 365, 

Earth's metallic bases of the, 358, 

Eggs, white of, 688, 690. 
coagulated, 690* 

Elaene, 656. 

Elaidic acid, 654. 

Elayl, 538. 

Electrical phenomena, 159. &c. 

Electrical theory as modified by Mr. Fa- 
raday, 162. 

Electricity of, 158. 
the voltaic circle, 157, et seq. 378, et 

passim. 
of friction and of high tension, 174. 

Elements: First class, 119; second, 119; 
third, 120; fourth, 120; fifth, 121; 
sixth, 121 ; seventh, 121 ; eighth, 
122; ninth, 122; tenth, 122; ele- 
venth, 122. Those without isomor- 
phous relations not classified, 122, et 
seq. Table of isamorphous elements, 



Elements, their arrangement in com- 
pounds, 129. 

names of, with their symbols and least 
combining proportions. 86, 87, 88. 
Ellagic acid, 637, 638. 
Emerald, 368. 
Emetine, 660, 664. 
Emulsin, 587. 
Enamel, 418. 
Enchelide monad, 690. 
Equivalents, or equivalent quantities, 92. 

definition of, 103. 
Eremacausis, 488. Definition of, 488. 
Erythrylin, 624. 
Erythrin, 624. 

bitter, 624. 

pseudo, 624. 
Erythrolein, 625. 
Esculin, 617. 
Etna], and the cetyl series of compounds, 

597. 
Ether, or sulphuric ether, 520 to 522. 

formation of, 525. 

carbonic, 528. 

chloropyromucic, 516. 

chloroxalic, and its compounds, 492, 
535, 536. 

chloroxi-carbonic, 529. 

cyanic, 529. 

formic, 564. 

hydrochloric, 491, 522. 

hippuric, 529, 

mucic, 515. • 

nitrous, 527. 

CDnanthic, 496, 556. 

oxalates of, 528. 

oxalic and its compounds, 492> 528. 

pyromucic, 516. 

salts of, 524. 

type, 499. 

acetic, 534. 

oxalic, 528. 

heavy chlorinated, 537. 

sericic, 648. 

veratric, 647. 
Etherine, 538. 
Ethers, theory of, 144, 525. 
Ethyl, 518. 

series of compounds of, 518, et seq.. 

cyanide of, 523. 

hydrated oxide of, 518. 

oxide of, 520. 

chloride of, 522. 

bromide of, 522. 

hippurate of oxide of, 529. 

iodide of, 522. 

the sulphuretsof, 522, et seq.. 

benzoate of oxide of, 529. 

bisulphuret of, 523. 

bicyan urate of oxide of, 529* 

seleaiuret of, 523. 



INDEX. 



737 



Ethyl, telluret of, 523. 
salts of oxide of, 524. 
acid sulphate of oxide of, 524. 
acid phosphate of, 527. 
sulphates, arseniate, carbonate, and ni- 
trate of its oxide with various sub. 
stances, 52/7528. 
protochlorinated chloride of, 501. 
relation between the series of ammo- 
nium and, 546. Tables 547 to 549. 
sulphocarbonate of oxide of ethyl and 

water, 529. 
transformations of the bodies contain- 
ing, 530. 
sulphate of oxide of, and of etherole, 

526, 530. 
acetate of oxide of, 534. 
products of the action of chlorine, bro- 
mine and iodine upon, 535. 
oxichloride of, 535. 
Euchlorine, 266. 

Euchrone, and euchronic acid, 634. 
Euclase, a silicate, 368. 
Eudiometer, Ure's, 208. 
Eupion, 571. 

Evaporation in vacuo, 64. Spontaneous, 75. 
Excrements, 707. 
Expansion, 25. Of solids, 26. 
of liquids, 28. 
of gases, 31. 
Extractive matter, 488. 
Eye of the, 713. Its aqueous and vitre- 
ous humours, cornea, crystalline lens, 
pigmentum nigrum, and scelerotica, 
713. 

Fahlerze, and formula of its composition, 

460. 
Fat and suet, 649, 687, 712. 
Feathers, constituents and material pro- 
perties of, 703. 
Fecula, 504. 
Felspar, 364. 
Fellinic acid, 706. 
Fermentation, 533, 156, 504, 551, 556. 

of sugar, 511, 518. 

by yeast, 509. 518. 

acetous, 533. 

vinous, 519. 

of vegetable juices, 519, 550. 

lactic and viscous, 550, et seq. 
Ferments, action of, 494. 
Ferric oxide, 390. 

acid, 122. 
Ferrocyanic acid, 500, 669. 
Ferrocyanides of copper, hydrogen, potas- 
sium, and those denominated double, 
669, et seq, 
Ferrocyanides, the, 669. 
Ferroso- ferric sulphate, 394 
Fibrin vegetable, 688, 691. 

animal, 712. 



Flame of coal gas, 302. 
Flint glass, 26. 

Fluidity as an effect of heat, 50. 
Fluids secreted and subservient to diges- 
tion, 703. 
Fluor spar, 348. 
Fluoride of silicon, 235. 

of boron, 285. 
Fluoride of aluminum, 361. 
Fluorine, specific gravity of, 115. 
Fluorine, of, 232. 
Fluosilisic acid, 285. 
Fluoboric acid, 285. 
Formiates the, 564. 

of ammonia, 564. 

of barytes, 565. 

of oxide of ethyl, 564. 

of cerium, 565. 

of lead, 565. 

of oxide of methyl, 565. 

of potash, 565. 

of soda, 565. 

of alumina, 565. 

of silver, 565. 

of suboxide and oxide of mercury, 565. 

of manganese, iron, zinc, cadmium, 
nickel, cobalt and copper, 565. 
Formic acid, obtained from red ants, 563, 
et seq. 

ether, 564. 
Formula of compounds, 93. 
Formyl, series of compounds, 562, et seq. 

compounds of, with chlorine, bromine 
and iodine, 566. 

chloride, bichloride and perchloride of, 
566, et seq. 

perbromide and periodide of, 567. 

sulphuretof, 567. 
Fousel oil, 552, 554. 
Freezing of water by its own evaporation, 

66. 
Friction, phenomena of electricity by, 174. 
Frost, 49, see Ice. 
Fruit, sugar and acids of, 513, 644. 
Fusctis pal mat us, 276. 
Fumaramide, 645. 
Fumaric acid, 645. 

ether, 645. 
Fumigation by nitric acid, 220. 
Fulminating ammoniaret of silver, 460. 
Fulminic acid, 137, 670, 673. 
Fulminates, 673. 

Gadolinite, the mineral, 126. 

Gahnite, an aluminate of zinc, 360. 

Galipot, 605. 

Gallic acids, 637. 

Galvanometer, with an engraving, 183. 

Gases, the liquefiable, 68, 74. 

diffusion of, 70. 

rushing of, into a vacuum, 73. 

their passage through membranes, 74. 
62* 



738 



INDEX. 



Gases, the permanent, 68. 

specific gravities of the, 110. 
Gaseous bodies, Table I of their specific 
gravities, 113. Table II and sym- 
bolic formula? of the same, 114. 
Gaseous state, relation between the atomic 
weights and volumes of bodies in the, 
107. 
Gastric juice, its agency, 703. 
Gaultheria, oil of, and bodies derived from 

it, 594. 
Gaylussite, 349. 

Gelatin, the basis of glue, size and animal 
jelly, 698. Products of its alteration 
and decomposition, 700. 

sugar, or glycicoll, 700. 
German silver or packfong, 399. 
Glass, of, 125, 338. 

composition of the varieties of, 339. 

expansion of, 26. 

unequal expansion by heat of plate, 27. 

white Bohemian, 339, 479. 

of antimony, 440. 

and platinum cemented together, 26. 
Globulin, 698. 
Glucic acid, 515. 
Glucina, the earth, 367. 
Glucinum, 367. 
Glucose, 513. 
Gluten, of, 509, 618, 688, 689. 

of indigo, 619. 

its conversion into yeast, 495. 
Glyceryl, of, 596. 

hydrate of oxide of, 596. 
Glycerin, 486, 596, et seq. 
Glycicoll, 700. 

Gold, its native form, crystallization, &c., 
464. 

quartation of the alloy, 464. 

chloride and sulphuret of, 465. 

peroxide of, 465. Oxide, 464. 

sesquisulpliuret, sesquichloride or per- 
ch loride of, 466. 

sesquibromide of, 467. 

iodide of, 467. 

chloride of potassium and, 467. 
of sodium and, 467. 
of ammonium and, 467. 

salts of (a fulminate and seleniate,) 467. 
Grape sugar, 513. 
Graphite, 117, 221. 

artificial, 221. 
Green, mineral, 404. 
Gum, of, 517, 685.' 

arabic, 517. 
' British corresponding with dextrin, 508. 

tragacanth, 517. 

resins, 615. 
Gunpowder, 323. 
Gypsum, 349. 

Hail, formation of, 208.. 



Hair, 701. 

Harmotome, 364. 

Heat, laws of, 25, et seq. Nature of, 80. 

central, of the earth, 49. 

specific, of atoms, 105. Capacities of 
compound atoms for heat, 107. 

conduction of, 41. 

radiation of, 43. 

of combustion, 190. 

absorption of, 51. 

assumption of latent, 52, 65. 

products of its action upon acetic acid 
and the acetates, 486, et seq. 

its transmission, through media, and the 
effect of screens, 45. 
Hedyphane, 350. 
Hellebore, white, 664. 
Hematite, red and brown, 381, 390. 
Hematosin,.697. 
Hematoxylin or hematin, 629. 
Hemlock, 664. 
Hesperidin, 618. 
Hippuric acid, 580. 
Honeystone, 634. 

Hornblende, a silicate of lime and mag- 
nesia, 357. 
Horny matter, compact, membranous, 701. 
Humboldite, 631. 
Humus, 488, 683. 

Hurricanes, rotatory evolution of, 207. 
Hyacinth, 369. 
Hydrate of bary tes, 342. 
Hydrates, definitions of the, 92. Ele- 
ments of various, 503- 
Hydriodates of ammonia, &c, 121. 
Hydriodic acid, 279. 
Hydrobenzamide, 502. 
Hydroboracite, of what substances com- 
bined, 357. 
Hydrochlorate of morphia, 661. 
Hydrochloric acid, 111, 262 ; of commerce, 
264. 

concentrated, 264. 

properties of, 262. 

tables of density, 263. 

ether, 491, 522. 
Hydrocyanic acid, 667, et seq. 

aqueous solution of, 667. 

how recognised, 668. 

antidote for, 667. 

tests for, 668. 
Hydrogen, 193 to 202. Oxide of, 197. 

and nitrogen, 290. 

and carbon, 299. 

the combining weight and volume of, 
109, 110. 

arsenietted, 435. 

selenietted, 289. 

sulphurets of, 287, et seq. 

a chlorous constituent of certain com 
pounds, 493. 

ferrocyanide of, 669. 



INDEX. 



739 



Hydrogen, peroxide of, 129, 201. 

Hydrobromic acid, 274. 

Hydrosulphuret of the sulphuret of ethyl, 

523. 
Hydruret of benzoyl, 501, 579. 
Hygrometers, 76. 
Hyoscyamine, 664. 
Hyperchloric acid, 91, 267. 
Hypochlorous acid, 265. 
Hyponitrous acid, 215. 
Hoponitric acid, 216. 
Hyposulphurous acid, 241. 
Hyposulphuric acid, 244. 

Ices for the table, 53. 
Ice, liquefaction of, 51, 53. 
Indigo, blue, 619, 621. 

sulphate of, 352, 621. 

gluten of, 619. 

brown, 619. 

red, 619, 620. 

white or reduced, 620. 

action of fused potash on, 621. 
Indigogen, 620. 
Indigotic acid, 622. 
Inductive affinity of, 156 to 184. 
Infection in hospitals averted by fumiga- 
tions, 220. 

matters productive of, 210. 
Ink, black, 636. 

red, 629. 
Insolubility, influence of, 151. 
Inulin, discovered in the root of Inula 

Helenium, 509. 
Iodal, an oleaginous liquid, 538. 
Iodates, salts of iodic acid, 280. 
Iodic acid, &c, 279. 
Iodides, 278, 281. 
Iodine, 121, 158, 275. 

discovered in kelp, 275* 

compounds of, 279. 

preparation of, 275. 

ley, prepared from kelp, 276. 

properties of, 277. 

uses in medicine, 278. 

action of, upon ethyl, acetyl and their 
compounds, 535. 

compounds of formyl with, 566, et seq. 
Ipecacuanha, 664. 
Iridium, 473. 

chlorides of, 474. 

oxides of, 473. 

sulphurets of, 474. 
Iron, native, 379, 380, 381. 

black oxide of, 381. 

specular or oligistic iron, 381, 390. 

red and brown hematite, 381, 390. 

spathic, 381. 

malleable, 384. 

stone, clay, 381. 

diagram of the blast furnace for smelt- 
ing it, 382. • 

solid slag of, 382. 



Iron, properties of, 384. 

converted into steel, 384. 

passive condition of, 385. 

observations on the oxidation of, 39L 

cast, 383. 

black or magnetic oxide of, 391. 

alum, 363, 393. 

bar possessing magnetism, its polarized 
condition, &c, 159. 

unequal expansion of cast, 28. 

clamps, atmospheric effects on, 27. 

wire, 26. 

arseniates of, 489. 

peroxide of, an antidote for arsenic, 391, 
439. 

benzoate and succinate of peroxide of, 
394. 

carbonate of, its formation, 389. 

ferrocyanide of potassium and, 3S8, 665, 
668. 

ferricyanide of, 388. 

lactate of protoxide of, 552. 

percompounds of, 390. 

perch loride of, 392. 

percyanide or sesquicyanide of, 392, 
669. 

period id e of, 392. 

pernitrate of, 394. 

peroxalate of, 394. 

peroxide of, 390. 

the persulphates of, 393. 

protacetate of, 390. 

protocompounds of, 387. 

protoxide of, 387. 

protosulphuret of, 387. 

protochloride of, 388. 

protiodide of, 388. 

protocyanide of, 388, 669. 

protonitrate of, 390. 

soluble protosalts of, 214. 

sesquiferrocyanide, 393, 669. 

sulphate of, 389. 

sesquisulphuret of, 392. 
Isomerism of, 127, et seq. 
Isomorphism, doctrine of, 115, et seq. 

objections to the principles of, 117. 
Isomorphous relations of elementary sub- 
stances, 119, et seq. 
Isomorphous elements, 123. 
Ivory black, 223. 

Jervine, 660, 664. 
Jeweller's putty, 418. 
Junipers, oil of, 605. 

Kaolin, 364, 366, et seq. 
Kelp, 275. 

produces the iodine ley, 276. 
Kermes mineral, 440. 
Kinates of silver, copper, lead, and lime, 

646. 
Kinic acid, 645. 
Kinoile, 646. 



740 



INDEX, 



Lactate of bary tes, 551. 

of lime, 551. 

of magnesia, 552. 

of urea, 552. 

of alumina, lead, mercury and nickel, 
552. 

of soda, potash and ammonia, 551. 

of silver and protoxide of iron, 552. 
Lactic and viscous fermentations, 550, et 
seq. 

acid, 551. 
Lactine, 515. 
Lake, the colour, 627. 
Lantanum, 445. 
Latent heat, 51. 

of vapours, 59. 
Lavender water, 601. 
Leaves, pure oxygen gas emitted by, 210. 
Lead, 407. 

suboxide of, 407. 

protoxide of, 138, 407. 

peroxide of, 408. 

red (minium,) 408. 

protosulphuret of, 409. 

chloride of, 409. 

iodide of, 409. 

cyanides of, 410, 669. 

carbonate of, 410. 

formiate of, 565. 

sulphate of, 411. 

silicate of, 125. 

insoluble seleniate of, 246. 

nitrates of, 411. 

the nitrites of, 411. 

acetates of, 412. 

alloys of tin and, 412. 

silver contained in, 413. 
Leather, various chemical treatments of, 
699. 

tawed, wash, and curried, 699. 
Leconorin, 626. 

Legumin, or vegetable casein, 618, 689. 
Lemons, oil of, 605. 
Leucin, 693. 
Leucite, 364. 
Leucol, 572. 
Lichen starch, 510. 
Lichens, properties of, 623. 
Light, mechanical properties of, 81. 
Common light, 82. Polarized light, 
82. Decomposition of, 83. 
Light, reflection and polarization of, 205, 

508. 
Lignin or woody fibre, 517. 

combines with neutral salts, 518. 
Lignin-sulphuric acid, 518. 
Lignone, 569. 
Lime uncombined, or quicklime, 346. 

acetate of, 534. 

carbonate of, 346, 349, 

hydrate of, 346. 

sulphate of, 349* 



Lime, oxalate of, 348, 632. 

hyposulphite of, 350. 

double carbonate of soda and, 349. 

lactate of, 551. 

nitrate of, 350. 

phosphates of, 350. 

chloride of, bleaching powder, 350. 

constitution of the chloride, 351. 

its carbonate dimorphous, 117. 

carbonates of, characterized, 119, 120. 

iodate of, 280. 

tartrate of, 641. 
Limestone, 346, 347. 
Limestone, magnesian, 355, 356. 
Liquation, 415. 
Liquefaction, intermediate condition of, 

50. 
Liquefied gases, 28. 
Liquids, expansion of, 28. 

produced by the condensation of gases, 
28. 

boiling point of, 55. 
Liquorice sugar, 516. 
Lithia, its hydrate, sulphate, phosphate, 

carbonate and chloride, 341. 
Lithia and alumina, silicates of, 364. 
Lithium, 341. 

oxide and chloride of, 341. 
Litmus, 623, 625. A re-agent, 626. 
Logwood, its use in dyeing, 629. 
Luminous phenomena of salts, &c. 126. 
Lymph, 707. 



Magistery of bismuth, 414. 
Magnesia, preparations of, 354. 

alba, the subcarbonate of pharmacy, 
355. 

carbonate of, 354. 

the sulphates of, 355, 356. 

nitrate of, 356. 

borate of, 357. 

silicates of, 357. 

phosphate of ammonia and, 357. 

bicarbonate of potash and, 355. 

aluminate of, 360. 

formiate of, 565. 

nigra, 370. 

usta, 354. 
Madder, of, 626, et seq* 

purple, red, yellow, orange, and brown, 
627. 
Magnesite, 354. 
Magnesian sulphates, 137. 
Magnesium, properties of, 354. 

chloride of, 354. 
Magnet, the, 159. 
Magnetic bar, representation of a, 159l 

power of certain metals, 371. 

ore, 381, 391. 
Magnetical induction, 159 to 161. 

polarity, 159, &c. 



INDEX. 



741 



Magnetism and magnetic phenomena, 
159 to 161, &c. 

theory of, 159. 

Austral, 159. 

Boreal, 159. 
Malachite, a native carbonate of copper, 

404. 
Malates, the, 645. 
Maleic acid, 645. 
Malic acid, or of apples, 644. 
Malleability of metals, 52, 307. 
Malt, 508. 

Manganese, 119, general description ofi 
370. 

deutoxide and protoxide, 89, 371, 
373. 

peroxide, 374, valuation of, 375. 

isomorphous relations of, 377. 

alum, 363. 
Manganic acid, 119, 375. 
Manna sugar, or mannite, 516, 550. 
Margarat.es, 649. 
Margaric acid, 649, 651, 
Margarone, 651. 
Marty clay, 366. 
Marshes, carburetted hydrogen of, 210. 

miasmata of, 210. 
Matter, dependence of electricity upon, 
158. 

combination of, its natural condition, 
498. 
Meconate of lead, (?35. 
Meconic acid, and its congeners, 634, et 

seq. 
Meerschaum, 357. 
Melam, 676. 
Melamine, 676. 
Melassic acid, 515. 
Mellitates, 633. 
Millite, a mineral, 634. 
Mellitic acid, 633. 
Melting of wax, tallow, sulphur and solid 

bodies, 52. 
Menispermine, 660. 
Mentbene, 609. 
Mercaptan, 119, 523. 
Mercaptide of mercury, 523. 
Mercurial column, its depression produced 

by water vapour, 65. 
Mercuric compounds, 451. 

nitrates, 456. 

sulphates, 456. 
Mercurous compounds, 448. 
Mercury, expansion of, 28, et seq. 

general account of, 447, et seq. 

analogies of, 122. 

acetate of, 451. 

black oxide of, 448. 

bromide of, 455. Sub-bromide of, 450. 

cyanide of, 455, 500. 

of potassium and, 456. 

tribasic cyanide of, 456. 



Mercury, fluid, repulsion of, 55. 
freezing of, 53. 
Hahnemann's soluble, 451. 
chloride of, 452. Subchloride of, 449. 
chloride of, ammonia and, 452. 
chloride and sulphuret of, 454. 
double salts of chloride of, 454. 
iodide of, 125, 455. Subiodide of, 

450. 
nitrates of, 450, 456, et seq. 
oxichloride of, 454. 
oxicyanide of, 456. 
red oxide of, 451. 
sulphate of, 450, 456. 
sulphuret of, 125, 449, 451. 
Mesite and mesiten, 569. 
Mesityle, oxide, chloride, and chloroplati- 

nate of oxide of, 542. 
Mesitylene, 541, bihydrate of, 540. 
Mesotype, 364. 
Metacechlorplatin, 542. 
Metacetone, a combustible liquid, 512, 

541. 
Metaldehyde, 532. 

Metals, the positive and the negative, of 
the voltaic circle, 164. Diagrams, 
166,- el seq. 
Metallic bases of the alkaline earths, 311, 
342. 
of the earths, 311, 358. 
Metals, expansion of, 26, et seq. Their 
contraction, 26. 
order of their affinity for nitric acid 

and oxygen, 149, 150. 
names and densities, 306. Fusibility 
of, 307. General properties, 308. 
Classification of, 311. 
sali-molecular structure of, 378. 
proper, having protoxides isomorphous 
with magnesia, with bismuth, &c. 
370, et seq. et passim. 
isomorphous with phosphorus, 433. 
formation of cyanides of, 665. 
Methol, 570. 

Methyl, series of compounds, 145, 558. 
chloride of, 559. 
iodide of, 559. 
oxide of, 558. 
hydrate of oxide of, 558. 
sulphurets, fluoride, cyanide, &c. of, 

559. 
oxygen salts of, 560; 
nitrate, carbonate, and oxalate of, 561. 
sulphates of oxide of, 560. 
acetate, benzoate, bicyanurate and mu- 

cate of oxide of, 561. 
oxide of, its compounds of an uncertain 

constitution, 561. 
and its derivatives, products of the de- 
composition of, 562. 
action of chlorine upon oxide and chlo- 
ride of, 568. 



?42 



INDEX, 



Methyl, products of the distillation of 
wood in relation to oxide of, 557, 
569. V 

Methylal, and formomethylal, 563. 
Methylic ether, 558. 
Miasmata, 210. 
Milk, sugar of, 515. 

properties and constituents of, 708. 

coagulated, as casein, 693. 
Mineral, fibrous, of CafFraria, 363. 

waters, salts of, analyzed, 155. 

factitious of Struve, &c. 155. 
Minium or red lead, 408. 
Molecular theory of organic compounds, 

Molecule, or chemical atom, 497. A 

complex organic, defined, 498. 
Molybdate of molybdic oxide, 429. 

of potash, 429. 

of soda, 429. 

the bi molybdate of soda, 429. 

of lead, 429. 

of magnesia, 429. 
Molybdenum, 122, 428. 

oxides of 428. 

chlorides of, 430. 

sulphurets of, 429. 
Molybdic acid, 429. 

oxide, 428. 
Molybdous oxide, 428. 
Morphine or morphia, 657, 659, 660. 
Moroxite, 350. 
Mortar, hydraulic, 347. 
Mosaic gold of the alchemists, 418. 
Mucic acid, 515. Modified, 515. 

ether, 515. 
Muriatic acid, 257, 262. 

process for, 262. 
Mushroom sugar, 516. 
Murexan, 682. 
Murexide, 681. 

Mucus, pus, and purulent matters, 707. 
Mulberry culculus, 710. 
Muscle, animal, 712. 

Naptha, napthene, and napthol, 575, 576. 

Naphtaline, 572. 

Napbtalin-hyposulphuric acid, &c, 573. 

Narceine, 660, 662. 

Narcotine, 659, 662. 

Natrium, 326. 

Natrolite, 364. 

Nerves of animals, tendons, ligaments and 

cartilages, 713. 
Nickel, as an allov affords imitations of 
silver, 397, 399. 

its characteristics, 398. 

oxides of, 398. 

carbonate of, 398. 

sulphuret of, 398. 

chloride of, 398. 

sulphate of, 398. 



Nicotine, 665. 
Nitrate of silver, 462. 
Nitrates of copper, 220. 

of magnesia, 220. 

of mercury, 450, 456. 

of potash, 217. 

the subnitrates defined, 220. 

of certain elements, 120. 
Nitre in certain earths, 217, 322. 
Nitric acid, 217 to 221. 

its action on margaric and stearic acids, 
652. 
Nitric oxide, preparation of this gas, 213. 

properties of, 214. 
Nitrocumide, 608. 
Nitrogen, 203. Free atmospheric, 684. 

its class, 121. 

and hydrogen, 290. 

estimation in organic analysis, 483, et 
seq. 

chloride of, 269. Iodide of, 281. 

deutoxide of, 213. 

peroxide of, 216. 
Nitronaphdehyde, 574. 
Nitronaphtalic acid, 574. 
Nitronaphtalide, 574. 
Nitronaphtalise, 574. 
Nitrous acid, 121, 216. 

gas, 213, 216. 

oxide, 211. 

its preparation, 211. 

its properties, 212. • 
Nomenclature and notation, chemical, 85, 

et seq. 
Nutmegs, oily acid of, 648. 
Nux vomica, 663. 

Oderiferous principles of plants and 

flowers, 210, 600. 
(Enanthic acid, 557. 

ether, 496, 556. 
Oils of anise, 607. 

of balsam of Peru and Tolu, 590. 

of bergamotte, 606. 

of camphor, 611. 

of caraways, 608. 

cajupet, 608. 

of cinnamon, 588. 

of cloves, 607. 

of copaiba, 606. 

of cubebs, 606. 

of cummin, 608. 

of elemi, 606. 

of bitter fennel, 607. 

of junipers, 605. 

of hysop, 608. 

laurel-turpentine, 606. 

of lemons, 605. 

of pepper, 606. 

of peppermint, 609. 

of savin, 606. 

of storax, 606. 



INDEX. 



743 



Oils, of turpentine, 602. 
lavender, 608. 
castor, 655. 
of cedar, solid, 609. 
of chamomile, 609. 
of roses, 609. 
of valerian, 609. 
of rnentha viridis, 609. 
of rue, 609. 

of mustard, volatile, 611. 
of grain-spirits or fousel oil, and bodies 

derived from it, 552. 
of ants, artificial, 556. 
of potatoes, 496, 552, 554. 
palm, 648. 

volatile of almonds, 486, 502, 579. 
of wine, sweet or heavy, 530. 
of wines, ethereal, 556. 
from seeds of croton tiglium, &c, 647. 
of gaultheria, 594. 
of spiraea, 502, 591. 
' xylite, 569. 
essential, 600. 

those containing no oxygen, 602. 
those containing oxygen, 606. 
those containing sulphur, 611. 
acids formed by sulphuric acid on the 

fat, 655. 
fixed, 28, 649. 
sweet principles of, 596. 
volatile, 600, et seq., 646. 
Oily acids, 646, 648, 649, 653, et seq. 
Oleates, 653. Of potash, soda, lead, &c, 

653. 
Oleene, 656, 713. 
Oleic acid, 653, and acids relating to it, 

654. 
Olefiant gas, 303, 491, 526. Its type, 499. 
Oleine, 653, 713. 
Oleophosphoric acid, 713. 
Olive oil, 649. 
Opium, 634. 
chemical bases of the white poppy, &c, 
150, 657, 659, 660, et seq. 
Optics, of, 82. 
Orcein of archil, 624. 
Orcin, 139, 624. 

Organic Chemistry, preliminary observa- 
tions, 478, et seq. 
compounds, molecular theory of, 497. 
radicals, 665. 

substances, definition, 478. Their com- 
position and analysis, 479. Trans- 
formation of, 485. 
acids, 631, 640. 
analysis, 479. 
bases, 656, 660. 

compounds, artificial processes pro- 
ducing modifications of, 485. 
processes of plants and animals, 683. 
Orpiment, 435. 
Osmic acid, 475. 



Osmium, 474, et seq. 

chlorides and oxides of, 475. 
Oxalates, 119, 632. 
Oxalic acid, 631. 
ether, and compounds derived from it, 
492. 
Oxamide, 291. 
Oxichlorides, 261. 
Oxides, definition of, 80. 
of antimony, 440. 
carbonic, 631. 
ferrous, 387. Ferric, 390. 
of hydrogen, 197, 201. 
of mercury, formiate of the suboxide 

and, 565. 
molybdic, 428. 
molybdous, 428. 
nitric, 213. 
nitrous, 211. 
of potassium, 119, 315. 
stannic, 417. 
stannous, 416. 

protoxide, deutoxide, peroxide, sesqui- 
oxide, tritoxide and suboxide, defined, 
89. 
composition of, 95. 

of ethyl in the form of sulphates, arseni- 
ate, nitrate, carbonate, &c, with 
other substances, 527, et seq. 
[*** For many of the Oxides see the 
metals, &c, nomijiatim.] 
Ox-bile, 704. 
Oxygen, 135 to 193. 
its class, 119. 
binary compounds of, 90. 
acid salts, 137, 145. 
affinity of metals for, 149, 150. 
absorption of, by alcohol, 438, 489. 
and nitrogen of atmospheric air, 209. 
action of free, 438. 
Oxygenated water, 129, 201. 

Paints, see colouring matters. 
Palladium, the metal, 471. 

protoxide, &c, of, 472. 

nitrate, peroxide, and bichloride of, 472. 
Palm oil, 648. 
Palmitic acid, 648. 
Palmitine, 649. 

Pancreatic juice, its agency, 704. 
Papaver somniferum, 634, 659, 660. 
Paracyanosren, 669. 
Paraffin, 570. 
Paramorphine, 662. 
Paranaphtaline, 575. 
Para tartaric or racemic acid, 643. 
Paratartrates, salts denominated, 644. 
Pectin, of, 599. 
Pendulum rod of clocks, 26. 
Periote (olivine or chrysolyte,) 357. 
Peroxide of iron, 390. 
Peroxides of metals, 116, 126. 



744 



JNDEX. 



Peroxide of manganese, valuation of, 375. 
Persulphates of iron, 393. Double per- 
sulphate of iron and sulphate of pot- 
ash, 393.- 
Peruvian bark, 602. 
Perspiration, human, 712. 
Pepsin, a peculiar animal principle, 695. 

acetate of, 696. 

hydrochlorate of, 696. 
Petalite, 364. 

Petrifactions, calcareous, 349. 
Phloretic acid, 595. 
Phloretin, 595. 
Phloridzin and the bodies derived from it, 

595. 
Phlorizein, 595. 

Phosphates, 253, see the various sub- 
stances nomination. 
Phosphates, tribasic, 137. Earthy, 685. 
Phosphorescent light of certain sub- 
stances, 511. 
Phosphoric acid, 116, 251. 

hydrates of, 251, 503. 
Phosphorous and hypo-phosphorous acids, 

249, 250. 
Phosphorus, its class, 121. 

its preparation and properties, 247. 

essential to animal organization, 246. 

chlorides of, 273. 

oxidation of, 247. 

oxide of, 248. Acids of, 249, &c. 

vapour, 115, 247. 
Phosphuretted hydrogen, 121, 297. 

bichloride of tin and, 419. 
Picamar, 571. 
Picrosmine, 357. 
Picrotoxin, 617. 
Picromel, or sugar in bile, 704. 
Pigments, see Colours. 
Pipe clay, 366. 
Piperin, 616. 
Pittacal, 571. 
Plants, ordinary constituents of, 599, 683. 

families of and particular, their consti- 
tuents, 616, el seq. 683. 

neutral principles, peculiar to certain, 
616. Food of, 683. 

See Vegeto-alkalies. 
Plaster of Paris, 350. 
Platinic oxide, 470. 
Platinocyanic acid, 670. 
Platinocyanide of hydrogen, 670. 
Platinous iodides and cyanides, 470. 
Platinum, its expansion uniform, 26, 27, 
et passim. 

its derivation from plata silver, 467. 

its properties, 468. 

chlorides and protochlorides of, 469, 
471. 
• action of spongy, 149, 468. 

black powder of, 468. 

bicyanide of, 670. 



Platinum, oxides of, 469, 470. 

nitrate of the chloramide of, 470. 

resin of, 542. 

sulphurets of, 469, 470. 
Plumbagin, 618. 
Plumbago, 221. 

crystals of, 117. 
Plumbocalcite, mineral, 120, 408. 
Pneumatic trough, the, 71, &c. 
Pneumatics, observations regarding che- 
mistry and, 74, 
Poisons, mineral, 436, 452, et passim. 

vegetable, 663, 664, 667, et passim. 

of ill-cured meat, 497. 
Polarity, doctrine of, 158. 

and induction, the chemical, 161, et 
seq. 
Polarization of light, 205. 
Poles and axis of the earth, 206. Currents 
of the polar atmospheric steam, 206. 
Polybasite, 460. 
Polychrome, 630. 
Poppy, the, 634, 659, 660. 
Populin, 618. 

Porcelain, substances used in the manu- 
facture of, 365. Dresden, 365. Se- 
vres, 366. Staffordshire, 366. Ber- 
lin, 366. 
Porphyroxine, 662. 

Potash, its relations with other substances, 
120, 316, 632, et passim. 

salts of, 321. 

and alumina, double silicates of, 364. 

sulphate of alumina and, 361. 

antimoniate of, 442. 

and antimony, oxalate and tartrate of, 
441. 

and magnesia, bicarbonate of, 355. 

croconate and rhodizonate of, 633. 

yellow chromate of, 424. 

bichromate, or red chromate of, 424. 

bichromate of chloride of, 424. 

hydrate of, 315. 

hypermanganate of, 121. 

nitrate of, 217, 322. 

oxalate of, 632. 

red prussiate of, 319. 

neutral tellurate of, 432. 

bitellurite of, 432. 

bistearate of, 650. 

tungstate of, 427. 
Potassium, 312. 

its class, 120. 

compounds of, 315, et seq. 

bichloride of tin, and, 419. 

cyanide of, 319. 

ferrocyanide of, 318,500, 668. 

ferricyanide of, 319, 500. 

sulphocyanide of, 320. 

double salts of chromium and, 422. 

protochloride of tin and, 417. 
Potato starch, 504. 



INDEX. 



745 



Potatoes, oil of, 496, 552, 554. 

it becomes acid in contact with air, 555. 

solanine from, 665. 
Potter's clay, 367. 
Protein, 692, modifications of, 690. 

formula, &c. of, 692. 
Protoxides of elementary bodies, 119, 120. 
Prussian blue, 388, 393, 668, 669. 
Prussiates, 666. 
Prussic acid, 667. 

antidotes for, 667. 
Pseudo-morphine, 660, 662. 
Pteleyl, nitrate of oxide of, 542» 

chloride of, 543. 
Pumice, 347. 
Purple of Cassius, 465. 
Pus, 707. 

Putrefaction of meat, 497. 
Puzzolano, 347. 
Pyrallolite, 357. 
Paramide, 634. 
Pyrene, 572. 
Pyroacetic spirit, 540. 
Pyrogallateoflead,638. 
Pyrogallic acid, 638. 
Pyrometers, 36. 
Pyrophorus, 362. 

Pyrotartaric acids, liquid and solid, 643. 
Pyroxanthin, 570. 
Pyroxene, 357. 
Pyroxylic spirit, 558. 
Pyrrol, 572. 

Quercitrin, yellow dye, 630. 
Quercitronic acid, 630. 
Quinic acid, 645. 
Quinine, 657, 659, 662. 
sulphate and subsulphate, &c, of, 663. 

Radiation of heat, 43, solar, 205. 

the cause of dews, 48. 
Radicals, the term, 131. 
Rain, causes of clouds, and, 207. 
Rays, chemical and de-oxidizing, 85. 
Red dyes, 626, 627, 628, et seq. 
Red lead, 408. 
Red precipitate, 45 L. 
Refraction of light, 82* 
Rennet, 695. 
Resinous varnishes, 614. 
Resins, of, 600, 613. 
Respiration, laws of, 685, et seq. 

effects on air by, 686. 
Retinylene, 608. 
Rhodium, the metal, 476. 

chloride, oxides, sulphate and eulphuret 
of, 476, 477. 

nitrate of, 477. 
Roccella tinctoria, 624. 
Rock salt, 328. 

Rotal action of chemical affinity, 378, 
note. 
63 



Rouge, the pigment, 628. 
Rutilin, 591. 

Sabadilline, 660. 

Saccharates of zinc, lead, potash, ammo- 
nia, &c. 511, 513. 
Saccharic acid, 512. 
Saccharine substances, 510, et seq. 
Sacchulmic acid, 515. 
Sacchulmine, 515. 
Safflower, 628. 

Saffron colour and croconic acid, 633* 
Saffron of antimony, 440. 
Sago, 505. 
Sal-ammoniac, 294. 
Sal-gem, 328. 
Salicin and bodies derived from its deconv 

position, 590. 
Salicyl series of compounds, 591. 
Salicylimide, 502, 592. 
Salhydramides, 593. 
Salicylous acid, 502, 592. 
Saliretin, 591. 
Saliva, of, 703. 

Salt, and the salt-radical, definitions, &c. 
132. 

common, 327. 

the binarseniate of potash* 435. 

of cyanogen, 669. 

Glauber's, 89, 332. 

lakes, 328. 

miCrocosmic, 138. 

-petre or nitre, 217. 

green crystalline salt from ammonium 
and platinum, 469. 

Peligot's, 424. 

Rochelle, 92. 

of tin, 416. 
Salts, definitions of the, 91. Of double 
salts, 92. 

law in the construction of, 133. 

haloid, 133. Amphide, 133. 

table of their solubility, 147. 

liquefaction of ice and snow by, 53. 

physical constitution of various, 116, 
130, et seq. 

binary constitution of, 130, 378. 

binary theory of, 133. Objections to, 
132 to 138, 141. 

various combinations of, defined, 91. 

of isolable radicals, 136. 

monobasic, 137. 

bibasic, 137. 

tribasic, 137. 

double, 139, 539. 

denominated subsalts, the, 138. 

of ammonia, 142. 

of barytes, 344, 565, 640. 

of barytes, strontian and lead isomor- 
phous, 346. 

of chromium, 363, 394, 422* 

of copper, 404* 



746 



INDEX. 



Salts of croconic acid, 633. 
Epsom, 356. 
of ether, 524. 
of gold, 467. 
Klauer's, 363. 

of lead, 346, 410, 512, 565, 579, 640. 
of magnesia, zinc, &c. 119, 354. 
of lime and calcium, 349, 578, 640. 
of margaric acid, 649. 
in mineral waters, 155. 
neutral, 133, 517, et passim. 
of phosphoric acid, 136. 
of potash and antimony, &c. 441. 
of silver, 461, et seq. 565. 
of soda, 329. 
stannic, 419. 
stannous, 417. 
of strontian, 345. 
telluric, 432. 
valeric, 556. 
of zinc, 400. 
Saltpetre, 217. 
Sap of plants, 156. 
Santonin, 616. 

Sausages, causes of poison of, 497. 
Sea-salt in solution, its evaporation, 

115. 
Sea-water, evaporation of, by culm, 328. 
Sebacic acid, 654. 

ether, 654. 
Sebates, 654. 

Secondary voltaic decompositions, 174, 
Secretions, animal; serving digestion, 

703, et seq. 
Seleniates, 246. 
Selenic acid, 246. 
Selenious acid, 245. 
Selenium, 119, 245. 
its properties, 245. 
oxide of, 245. 
and hydrogen, 289. 
Sericic acid, 64S. 

ether, 648. 
Sericine, 648. 
Serous liquids, &c. 707. 
Serpentine, 357. 
Silica, 231. 
Silicates, 232. 
of alumina, 364, et seq. 
of lime and magnesia, 357. 
of lithia and alumina, 364. 
of lime and alumina, 365. 
of magnesia and alumina, 365« 
Silicic acid, 122, 231. 
Silicium, 230. 
Silicon, 122, 230. 
chloride of, 272. 
Silver, 458. 
pure, 459. 
native, 458, 463. 
ammoniaret of, 460. 
oxides of, 459, et seq*. 



Silver, acetate of, 463. 
bromide of, 461. 
benzoate of, 579. 
chloride of, 460. 
cyanide of, 461. 
carbonate of, 461. 
sulphuret of, 120, 460. 
sulphate of, 461. 
hyposulphate of, 461. 
hyposulphite of, 462. 
iodide of, 461. 
nitrate of, 462. 
nitrite of, 463. 
ammonio-nitrate of, a test of arsenious 

acid, 436. 
oxalate of, 463, 632. 
peroxide of, 463. 
lactate of, 552. 
valerate of, 556. 
alloys of, 463. 
Skin of animals, of the, 712. 
Sky, blue colour of the, 205. 
Smelting of clay iron-stone. Flux. Slag 

and Hot blast, 382. 
Snow, its formation, 208. 

liquefaction of by salts, 53. 
Soapstone, 365. 
Soaps of vegetable oils, 648. 
Soda, and its solutions, 327. 
arseniate of, 116. 
binarseniate of, 435. 
carbonate of, 329. 
the anhydrous carbonate, 329. 
the carbonate prepared from its sul- 
phate, 333. 
bicarbonate of, 331. 
the sesquicarbbnate, 332. 
felspar, 364. 
hydrate of, 327. 

nitrate of, of S. America, 217, 335. 
oxalate of, 632. 
phosphate of, 116, 335. 
reverberatory furnace for the making 

of, 333. 
salts of, 329. 
acid tungstate of, 427. 
Sodalite, 364. 

Sodium or natrium, its classification, 120, 
326. 
compounds of, 327. 
chloride of, 327. 
sulphurets of, 327. 
bromide of, 328. 
iodide of, 328. 

double cyanides of potassium and, 669. 
Solanine, 660, 665. 
Solar rays, 81, et seq. 206. 
Solid bodies, their expansion, 26. 

liquefaction, or partial liquefying of, 5. 
Solubility of the salts, diagram, 147. 
Solution and solvent powejs, 146. 
Spar, calcareous, 26. 



INDEX. 



747 



Spar, Iceland, 82. 

fluor, 348. 
Specific gravities of the gases, 110, tables, 
113, 114. 

of metals, 306. 

heat, 39. 

of atoms, 105. 
Spectrum, 83, black lines in, 84. 

rays of heat in, 84, chemical rays, 85. 
Speiss, 397. 

Spinell, an aluminate of magnesia, 360. 
Spireea oil of, 502. 
Spirit, wood, 558. 
Spirits, rectified, 519. 

proof, 519. 

grain, oil of, 552, 554. See alcohol. 
Spodumene, 364. 
Stalactites, their formation, 349. 
Stannous oxide, 416. 
Staphisaine, 660. 
Starch, fecula or amylin, 504, 685. 

gelatinous, 505. 

granules of, 506. 

gum, 503. 

mucilaginous, 507. 

sugar of, 503, 508, 513. 

inulin, 509. 

lichen, 510. 

potato, 504, 513. 

sour water of the manufacture of, 551. 
Steam, 57, et seq. 

engine, illustrations of the, 61, et seq. 

engines, boilers of locomotive, 63. 

specific gravity of, 111. 

passed over red hot iron, 151. 

the origin of certain colours of the at- 
mosphere and clouds, 205. 
Stearates, neutral, 650. 
Stearic acid, 649, 650. 
Stearine, 651. 
Steatite, 357. 

Steel, conversion of iron into, 384. 
Stilbite, lustrous, 365. 
Stoneware, 366. 

pink colour of, 367, 421. 
Strontian, strontia or strontites, 344. 

carbonate, sulphate, hyposulphite, and 
nitrate of, 345. 
Strotianite, 345. 
Strontium, 344. 

peroxide of, 345. 

chloride of, 345. 
Strychnine or strychnia, 659, 663. 
Stucco, its composition, 350. 
Suberic acid, 518, 652. 
Subnitrates possessing excess of metallic 

oxide, 220. 
Subsalts, account of the, 138. 
Substances, simple, 89. 
Substitution, 152, 490. 
Succinate of peroxide of iron, 394. 
of ammonia, etc., 652. 



Succinic acid, 652. 

Suet, 649. 

Sugar of; 139, 510, 635. 

cane, 510. 

loaf and muscovado, 510. 

compound of lime and, 511, 

compound of oxide of lead and, 512. 

candy, 510, 511. 

compound of chloride of sodium and, 512. 

grape, 513. 

of fruits, 513. 

diabetic, 513. 

compounds of grape, 514. 

insipid, 516. 

liquorice, 516. 

manna, or mannite, 516. 

melted, 52, 511. 

of milk, 515, 708. 

starch, 513. 

products of the fermentation of, 513, et 
seq. 
Sulphamide, 291. 

Sulphates, 116, 117, 113. The term de- 
fined, 239. 

of copper, 116, 404. 

ferrous, 339. 

of oxide of ethyl (and water,) 524. 

of lime and soda, double, 534. 

the magnesian, 137. 

and bisulphate of morphia, 662. 

neutral, 134. 

of strontian, 345. 
Sulphatoxide, the term, 131. 
Sulphocyanogen, 500, 674. 
Sulphatoxygen, the term, 131. 
Sulpholeic acid, 655. 
Sulphomargaric acid, 655. 
Sulphonaphtalide, 573. 
Sulphonaphtaline, 573. 
Sulphosaccharic acid, 514. 
Sulphovinic acid. 524. 
Sulphovinales, 527. 
Sulphur, 232, et seq. 

chloride of. 273. 

its class, 119. 

acids, the, 91. 

bases, 119. 

crystalline forms of, 117, 124. 
Sulphuret, ferric, 392. 

of potassium, 119, 317. 
Sulphurets, composition of, 96. 
Sulphuretted hydrogen, 234. 

its preparation and properties, 237. 
Sulphuretted sulphites, 241. 
Sulphuric acid, 236. 
affinities, &c, 150. 
hydrates of, 239. 
its action on the fat oils, 655. 
Sulphurous acid gas, 69, 234, 503. 
Sun's heat on the surface of the earth, 49. 
what termed chemical rays of the, 85. 
Symbols of chemical elements, 86 to 88. 



748 



INDEX. 



Synaptase of, 586. 

Tables, of chemical nomenclature and no- 
tation, 86, 87, 88. 
specific gravity of gaseous bodies, 113, 

114. 
of isomorphous elements, 123. 
of metals according to their electric re- 
lations, 170. 
of metals, 306. Fusibility of, 307. 
of classification of, 311. 
of corresponding compounds of acetyl 

and amidogen, 547, 548, 549. 
of the ethylic and amylic series, 553. 
Tanners, spent ley of the, 551. 
Tannates, the; of antimony, ammonia, 

potash, and of peroxide of iron, 636. 
Tannic acid, 635. 
Tannin, 635, 636. 
Tannogelatin, 636. 
Tantalum, 446. 
Tantalic oxide, 446. 

acid, 447. 
Tapioca, 505. 
Tar, products of the distillation of wood 

contained in, 570. 
Tartar, cream of, 641, 
Tartaric and paratartaric acids, and the 
products of their decomposition, 640, 
et seq. 
Tartralic and tartrelic acids, 643. 
Tartrate of potash and iron, 390, 394. 
Tartrates, 641 ; see various substances, 

nominatim. 
Taurin, how prepared, 705. 
Telluretted hydrogen, 432. 
Telluric acid, 431. Alphatelluric acid, 432. 
Tellurites, 431. 
Tellurium, 119, 430. 

sulphurets of, 432. Chlorides of, 432. 
Tellurous acid, 430. Alphatellurous acid, 

431. 
Temperature, effects of changes of, 26, 50, 
54, &c. 
of the atmosphere, 205, et seq. 
equilibrium of, 48. 
Test acid, 337. 

paper, 331. 
Teeth, of the, 712. 
Thebaine, 661, 662. 
Thermometer, the, 33, et seq. 
by Breguet, 27. 
self registering, 38. 
Thermo-electrical phenomena, 179. 
Thermo-multiplier, the, 46. 
Thorina, 368. 
Thorite, 368. 
Thorium, 119, 368. 

Tin, its classification, 121. General ac- 
count of, 415. 
mines, 415. 
stream, 415. 



Tin, grain, 415. 

block or ordinary, 415. 

properties of pure, 415. 

stone, crystals of, 417. 

bichloride of, 418. Of ammonia and, 
419, etc. 

bisulphuret of, 418, 419. 

carbonate of, 417. 

deutoxide of, 417. 

peroxide of, 122, 417. 

hydrated peroxide of, 418. 

protoxide of, 416. 

protochloride of potassium and, 417. 

anhydrous protochloride of, 416. 

protiodide of, 417. 

protosulphate of, 417. 

protonitrate of, 417. 

tartrate of potash and, 417. 

nitrate of peroxide of, 419. 

sulphate of peroxide of, 419. 

alloys of, 419. 

alloys of lead and, 412. 
Titanate of iron, 390. 
Titanic acid, 122, 41Q, 420. 

its sulphate, 420. 
Titanium, its class, 121. The metal, 419. 

oxide of, 420. 

bichloride of, 420. 

bisulphuret of, 420. 

bifluoride of, 420. 
Tobacco, seeds of nicotiana or, 665. 
Tolu, balsam of, 590. 
Topaz and quartz, fluids in minute cavities 

of, 28. 
Triphane or spodumene, 364. 
Tungstate of potash, 427. 

of soda, 427. 

of soda, acid, 427. 
Tungsten, 122; form of the element, 426. 

sulphurets of, 427. 

bichloride of, 428. 

terchloride of, 428. 
Tungstic acid, 427. 

oxide, 427. 
Turpentine, oil of, 602. 

resin of, 604. 

Uranium, 443. Protoxide and peroxide of 

443, 444. 
Uranic and uranous oxide, 443, 444. 
Urea, 501, 658, 665, 671. 

lactate of, 552. 
Urethane, 529. 
Urethylane, 561. 
Uramile and uramilic acid, 680. 
Uric acid, 665, 667, 711. 
Urine, 709. 

of diabetes, 513. 

of the horse, 581. 
Urinary concretions, 710. 

Valerate of silver, 556. 



INDEX. 



749 



Valerate of soda, 556. 

of potash and barytes, 556. 
Valerian root, its odour, 555. 
Valeric or valerianic acid, 555. 

aldehyde, 555. 
Vanadiates, the, 120. 
Vanadic acid, 426. 
Vanadium, 425. 

protoxide of, 426. 

peroxide of, 426. 
Vaporization, 54, et seq. 

effect of pressure on, 55. 
Vapour of water, its specific gravity, cal- 
culated from its density, 111. 

table of elastic force of, 718. 
Vapours, atmospheric, 207. 
Varnishes, resinous, 614. 
Vegetation, 209, 683. 
Vegeto-aikalies, 656, et seq. 
Veratrine, 660, 664. 
Veratrum album, 660, 664. 
Verdigris, distilled ; a green salt of copper, 

406. 
Vermilion, 125. 
Vinegar, of, 533, et seq. 

wood, 533. 
Viscous and lactic fermentations, 550, et 

seq. 
Vitrification, of, 125. 
Vitriol, blue, 404. 

white, 400. 

green, 389. 

oil of, 236. 
Voltaic circle, the chemical theory of the, 
378. 

simple, 157 to 159. Diagrams, illustra- 
tive of its connecting wire, &c, 163, 
et seq. 

the compound, 166, et seq. 

solid elements of the, 169, et seq. 

the liquid elements, 171, 174. 

decomposition by, 172. 

secondary, 174. 

instruments, 180. 
Volta-meter, 183. 

Wagon boiler, delineations of the, 62. 
Water, composition and properties, 197, 
et seq. 
its influence on chemical reactions, 132, 

note. 
its boiling point, 56. Its expansion, 28, 

60. 
constitutional, replaced by a salt, 138* 
Waters, mineral, 200, 349. 
Wheaten fluor, gluten from, 618. 



White lead, or ceruse, 410. 
White precipitate, 453. 
Winds, causes of, 206. 
Wines, ethereal oil of, 556. 

bouquet of, 556. 
Wolfram, 426. 
Wood, properties of, 517, et seq. 

of oak saw dust, 488. 

products of the dry distillation of, 557 v 

spirit, 558. 

products of the distillation of wood 
having some relation to the oxide of 
methyl, 569, et seq. 

those contained in tar, 570. 

coal, 487. 
Woody fibre or lignin, 514, 517. 
Wool, 702. 
Wort, sugar of, 509. 

Xanthic oxide, 710. 
Xanthoproteic acid, 693. 
Xylite and lignone, 569. 

naphtha, 569. 

oil, 569. 

resin, 569. 
Xylitic acid, 569. 

Yeast, action of, 156, 495. See fermenta- 
tion. 
Yellow, king's, 435. 
of berberin, 630. 
Yttria, the protoxide, 36S. 
Yttrium, 119, 368. 

Zaffre, 395. 

Zeolites, the, 365. 

Zero of Fahrenheit's scale, 53. 

Zinc, aluminate of, 360. 

alloys of, 401. 

blende, 399. 

bloom, 400. 

principal ores of, 399. 

chloride, iodide, sulphuretof, 400. 

nitrate, phosphate and silicate of, 401. 

plates and solution of, 156, et seq. (see 
voltaic circle, &c.) 

and copper plates, 158. 

and acid in contact, 161. 

and mercury, (amalgam of,) 164. 

salts of, 401. 
Zincoid, the term, 169. 
Zincous, positive, and basic elements, 498. 
Zirconia, 369. 

salts of, 369. 
Zirconium, 369. 

fluoride of, 120. 



THE END. 



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